Articles de revues : « Secretina »

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Park, Hyung Seo, Hyeok Yil Kwon, Yun Lyul Lee, William Y. Chey et Hyoung Jin Park. « Role of GRPergic neurons in secretin-evoked exocrine secretion in isolated rat pancreas ». American Journal of Physiology-Gastrointestinal and Liver Physiology 278, n^o 4 (1 avril 2000) : G557—G562. http://dx.doi.org/10.1152/ajpgi.2000.278.4.g557.

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Effects of intrapancreatic gastrin-releasing peptide (GRP)-containing neurons on secretin-induced pancreatic secretion were investigated in the totally isolated perfused rat pancreas. Electrical field stimulation (EFS) increased secretin (12 pM)-induced pancreatic secretions of fluid and amylase. EFS induced a twofold increase in GRP concentration in portal effluent, which was completely inhibited by tetrodotoxin but not modified by atropine. An anti-GRP antiserum inhibited the EFS-enhanced secretin-induced secretions of fluid and amylase by 12 and 43%, respectively, whereas a simultaneous infusion of the antiserum and atropine completely abolished them. Exogenous GRP dose-dependently increased the secretin-induced pancreatic secretion with an additive effect on fluid secretion and a potentiating effect on amylase secretion, which was not affected by atropine. In conclusion, excitation by EFS of GRPergic neurons in the isolated rat pancreas results in the release of GRP, which exerts an additive effect on fluid secretion and a potentiating effect on amylase secretion stimulated by secretin. The release and action of GRP in the rat pancreas are independent of cholinergic tone.

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Solomon, Travis E., John H. Walsh, Louis Bussjaeger, Yumei Zong, James W. Hamilton, F. J. Ho, Terry D. Lee et Joseph R. Reeve. « COOH-terminally extended secretins are potent stimulants of pancreatic secretion ». American Journal of Physiology-Gastrointestinal and Liver Physiology 276, n^o 4 (1 avril 1999) : G808—G816. http://dx.doi.org/10.1152/ajpgi.1999.276.4.g808.

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Posttranslational processing of preprosecretin generates several COOH-terminally extended forms of secretin and α-carboxyl amidated secretin. We used synthetic canine secretin analogs with COOH-terminal -amide, -Gly, or -Gly-Lys-Arg to examine the effects of COOH-terminal extensions of secretin on bioactivity and detection in RIA. Synthetic products were purified by reverse-phase and ion-exchange HPLC and characterized by reverse-phase isocratic HPLC and amino acid, sequence, and mass spectral analyses. Secretin and secretin-Gly were noted to coelute during reverse-phase HPLC. In RIA using eight different antisera raised against amidated secretin, COOH-terminally extended secretins had little or no cross-reactivity. Bioactivity was assessed by measuring pancreatic responses in anesthetized rats. Amidated canine and porcine secretins were equipotent. Secretin-Gly and secretin-Gly-Lys-Arg had potencies of 81 ± 9% ( P > 0.05) and 176 ± 13% ( P < 0.01), respectively, compared with amidated secretin, and the response to secretin-Gly-Lys-Arg lasted significantly longer. These data demonstrate that 1) amidated secretin and secretin-Gly are not separable under some chromatographic conditions, 2) current RIA may not detect bioactive COOH-terminally extended forms of secretin in tissue extracts or blood, and 3) the secretin receptor mediating stimulation of pancreatic secretion recognizes both amidated and COOH-terminally extended secretins.

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Possot, Odile M., Guillaume Vignon, Natalia Bomchil, Frank Ebel et Anthony P. Pugsley. « Multiple Interactions between Pullulanase Secreton Components Involved in Stabilization and Cytoplasmic Membrane Association of PulE ». Journal of Bacteriology 182, n^o 8 (15 avril 2000) : 2142–52. http://dx.doi.org/10.1128/jb.182.8.2142-2152.2000.

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ABSTRACT We report attempts to analyze interactions between components of the pullulanase (Pul) secreton (type II secretion machinery) fromKlebsiella oxytoca encoded by a multiple-copy-number plasmid in Escherichia coli. Three of the 15 Pul proteins (B, H, and N) were found to be dispensable for pullulanase secretion. The following evidence leads us to propose that PulE, PulL, and PulM form a subcomplex with which PulC and PulG interact. The integral cytoplasmic membrane protein PulL prevented proteolysis and/or aggregation of PulE and mediated its association with the cytoplasmic membrane. The cytoplasmic, N-terminal domain of PulL interacted directly with PulE, and both PulC and PulM were required to prevent proteolysis of PulL. PulM and PulL could be cross-linked as a heterodimer whose formation in a strain producing the secreton required PulG. However, PulL and PulM produced alone could also be cross-linked in a 52-kDa complex, indicating that the secreton exerts subtle effects on the interaction between PulE and PulL. Antibodies against PulM coimmunoprecipitated PulL, PulC, and PulE from detergent-solubilized cell extracts, confirming the existence of a complex containing these four proteins. Overproduction of PulG, which blocks secretion, drastically reduced the cellular levels of PulC, PulE, PulL, and PulM as well as PulD (secretin), which probably interacts with PulC. The Pul secreton components E, F, G, I, J, K, L, and M could all be replaced by the corresponding components of the Out secretons of Erwinia chrysanthemi and Erwinia carotovora, showing that they do not play a role in secretory protein recognition and secretion specificity.

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Villanger, O., T. Veel et M. G. Raeder. « Secretin causes H+ secretion from intrahepatic bile ductules by vacuolar-type H(+)-ATPase ». American Journal of Physiology-Gastrointestinal and Liver Physiology 265, n^o 4 (1 octobre 1993) : G719—G724. http://dx.doi.org/10.1152/ajpgi.1993.265.4.g719.

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Intrahepatic bile duct epithelial cells contribute to bile formation by hormone-dependently secreting HCO3- to bile and H+ to periductular fluid. The present study was undertaken to determine whether the secretin-induced H+ secretion is due to activation of a H(+)-ATPase or Na(+)-H+ exchange. H+ secretion was estimated from the rate of intracellular pH (pHi) recovery after acid loading (24 mM NH4Cl) of microdissected bile ductules from pig liver mounted in a flow-through chamber on the stage of a microscope. pHi was measured from an estimated average of 10-15 epithelial cells using the fluorescent pHi indicator 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein and dual-wavelength excitation of fluorescence. The ducts were superfused with HCO3(-)-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffers. We found that secretin induced net H+ secretion of 4.53 +/- 0.7 mumol.ml cell volume-1 x min-1. This H+ secretion was blocked by 10(-6) M bafilomycin A1 but was unaffected by Na+ substitution with choline in the superfusion buffer. The experiments also showed that bafilomycin A1 did not block Na(+)-H+ exchange. The secretin-induced H+ secretion is probably caused by a vacuolar-type H(+)-ATPase and may constitute an important element of the cellular mechanisms causing secretin-dependent ductular HCO3- secretion into bile

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Frank, Steven A. « Microbial secretor–cheater dynamics ». Philosophical Transactions of the Royal Society B : Biological Sciences 365, n^o 1552 (27 août 2010) : 2515–22. http://dx.doi.org/10.1098/rstb.2010.0003.

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Microbial secretions manipulate the environment and communicate information to neighbours. The secretions of an individual microbe typically act externally and benefit all members of the local group. Secreting imposes a cost in terms of growth, so that cheaters that do not secrete gain by sharing the benefits without paying the costs. Cheaters have been observed in several experimental and natural settings. Given that cheaters grow faster than secretors when in direct competition, what maintains the widely observed patterns of secretion? Recent theory has emphasized the genetic structure of populations, in which secretors tend to associate spatially with other secretors, reducing direct competition and allowing highly secreting groups to share mutual benefits. Such kin selection can be a powerful force favouring cooperative traits. Here, I argue that, although kin selection is a factor, the combination of mutation and demographic processes dominate in determining the relative fitness of secretors versus cheaters when measured over the full cycle of microbial life history. Key demographic factors include the local density of microbes at which secretion significantly alters the environment, the extent to which secretion enhances microbial growth and maximum local density, and the ways in which secretion alters colony survival and dispersal.

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Blocker, Ariel, Pierre Gounon, Eric Larquet, Kirsten Niebuhr, Véronique Cabiaux, Claude Parsot et Philippe Sansonetti. « The Tripartite Type III Secreton of Shigella flexneri Inserts Ipab and Ipac into Host Membranes ». Journal of Cell Biology 147, n^o 3 (1 novembre 1999) : 683–93. http://dx.doi.org/10.1083/jcb.147.3.683.

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Bacterial type III secretion systems serve to translocate proteins into eukaryotic cells, requiring a secreton and a translocator for proteins to pass the bacterial and host membranes. We used the contact hemolytic activity of Shigella flexneri to investigate its putative translocator. Hemolysis was caused by formation of a 25-Å pore within the red blood cell (RBC) membrane. Of the five proteins secreted by Shigella upon activation of its type III secretion system, only the hydrophobic IpaB and IpaC were tightly associated with RBC membranes isolated after hemolysis. Ipa protein secretion and hemolysis were kinetically coupled processes. However, Ipa protein secretion in the immediate vicinity of RBCs was not sufficient to cause hemolysis in the absence of centrifugation. Centrifugation reduced the distance between bacterial and RBC membranes beyond a critical threshold. Electron microscopy analysis indicated that secretons were constitutively assembled at 37°C before any host contact. They were composed of three parts: (a) an external needle, (b) a neck domain, and (c) a large proximal bulb. Secreton morphology did not change upon activation of secretion. In mutants of some genes encoding the secretion machinery the organelle was absent, whereas ipaB and ipaC mutants displayed normal secretons.

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Seo, Jin, Anja Brencic et Andrew J. Darwin. « Analysis of Secretin-Induced Stress in Pseudomonas aeruginosa Suggests Prevention Rather than Response and Identifies a Novel Protein Involved in Secretin Function ». Journal of Bacteriology 191, n^o 3 (21 novembre 2008) : 898–908. http://dx.doi.org/10.1128/jb.01443-08.

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ABSTRACT Secretins are bacterial outer membrane proteins that are important for protein export. However, they can also mislocalize and cause stress to the bacterial cell, which is dealt with by the well-conserved phage shock protein (Psp) system in a highly specific manner. Nevertheless, some bacteria have secretins but no Psp system. A notable example is Pseudomonas aeruginosa, a prolific protein secretor with the potential to produce seven different secretins. We were interested in investigating how P. aeruginosa might deal with the potential for secretin-induced stress without a Psp system. Microarray analysis revealed the absence of any transcriptional response to XcpQ secretin overproduction. However, transposon insertions in either rpoN, truB, PA4068, PA4069, or PA0943 rendered P. aeruginosa hypersensitive to XcpQ production. The PA0943 gene was studied further and found to encode a soluble periplasmic protein important for XcpQ localization to the outer membrane. Consistent with this, a PA0943 null mutation reduced the levels of type 2 secretion-dependent proteins in the culture supernatant. Therefore, this work has identified a novel protein required for normal secretin function in P. aeruginosa. Taken together, all of our data suggest that P. aeruginosa lacks a functional equivalent of the Psp stress response system. Rather, null mutations in genes such as PA0943 may cause increased secretin-induced stress to which P. aeruginosa cannot respond. Providing the PA0943 mutant with the ability to respond, in the form of critical Psp proteins from another species, alleviated its secretin sensitivity.

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Pugsley, Anthony P., Nicolas Bayan et Nathalie Sauvonnet. « Disulfide Bond Formation in Secreton Component PulK Provides a Possible Explanation for the Role of DsbA in Pullulanase Secretion ». Journal of Bacteriology 183, n^o 4 (15 février 2001) : 1312–19. http://dx.doi.org/10.1128/jb.183.4.1312-1319.2001.

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ABSTRACT When expressed in Escherichia coli, the 15Klebsiella oxytoca pul genes that encode the so-called Pul secreton or type II secretion machinery promote pullulanase secretion and the assembly of one of the secreton components, PulG, into pili. Besides these pul genes, efficient pullulanase secretion also requires the host dsbA gene, encoding a periplasmic disulfide oxidoreductase, independently of disulfide bond formation in pullulanase itself. Two secreton components, the secretin pilot protein PulS and the minor pseudopilin PulK, were each shown to posses an intramolecular disulfide bond whose formation was catalyzed by DsbA. PulS was apparently destabilized by the absence of its disulfide bond, whereas PulK stability was not dramatically affected either by adsbA mutation or by the removal of one of its cysteines. The pullulanase secretion defect in a dsbA mutant was rectified by overproduction of PulK, indicating reduced disulfide bond formation in PulK as the major cause of the secretion defect under the conditions tested (in which PulS is probably present in considerable excess of requirements). PulG pilus formation was independent of DsbA, probably because PulK is not needed for piliation.

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Honzawa, Norikiyo, Kei Fujimoto, Masaki Kobayashi, Daisuke Kohno, Osamu Kikuchi, Hiromi Yokota-Hashimoto, Eri Wada et al. « Protein Kinase C (Pkc)-δ Mediates Arginine-Induced Glucagon Secretion in Pancreatic α-Cells ». International Journal of Molecular Sciences 23, n^o 7 (4 avril 2022) : 4003. http://dx.doi.org/10.3390/ijms23074003.

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The pathophysiology of type 2 diabetes involves insulin and glucagon. Protein kinase C (Pkc)-δ, a serine–threonine kinase, is ubiquitously expressed and involved in regulating cell death and proliferation. However, the role of Pkcδ in regulating glucagon secretion in pancreatic α-cells remains unclear. Therefore, this study aimed to elucidate the physiological role of Pkcδ in glucagon secretion from pancreatic α-cells. Glucagon secretions were investigated in Pkcδ-knockdown InR1G9 cells and pancreatic α-cell-specific Pkcδ-knockout (αPkcδKO) mice. Knockdown of Pkcδ in the glucagon-secreting cell line InR1G9 cells reduced glucagon secretion. The basic amino acid arginine enhances glucagon secretion via voltage-dependent calcium channels (VDCC). Furthermore, we showed that arginine increased Pkcδ phosphorylation at Thr505, which is critical for Pkcδ activation. Interestingly, the knockdown of Pkcδ in InR1G9 cells reduced arginine-induced glucagon secretion. Moreover, arginine-induced glucagon secretions were decreased in αPkcδKO mice and islets from αPkcδKO mice. Pkcδ is essential for arginine-induced glucagon secretion in pancreatic α-cells. Therefore, this study may contribute to the elucidation of the molecular mechanism of amino acid-induced glucagon secretion and the development of novel antidiabetic drugs targeting Pkcδ and glucagon.

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Park, Hyung Seo, et Hyoung Jin Park. « Effects of γ-aminobutyric acid on secretagogue-induced exocrine secretion of isolated, perfused rat pancreas ». American Journal of Physiology-Gastrointestinal and Liver Physiology 279, n^o 4 (1 octobre 2000) : G677—G682. http://dx.doi.org/10.1152/ajpgi.2000.279.4.g677.

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Because GABA and its related enzymes have been determined in β-cells of pancreas islets, effects of GABA on pancreatic exocrine secretion were investigated in the isolated, perfused rat pancreas. GABA, given intra-arterially at concentrations of 3, 10, 30, and 100 μM, did not exert any influence on spontaneous or secretin (12 pM)-induced pancreatic exocrine secretion. However, GABA further elevated CCK (10 pM)-, gastrin-releasing peptide (100 pM)-, or electrical field stimulation-induced pancreatic secretions of fluid and amylase dose dependently. The GABA (30 μM)-enhanced CCK-induced pancreatic secretions were completely blocked by bicuculline (10 μM), a GABAA receptor antagonist, but were not affected by saclofen (10 μM), a GABAB receptor antagonist. The enhancing effects of GABA (30 μM) on CCK-induced pancreatic secretions were not changed by tetrodotoxin (1 μM) but were partially reduced by cyclo-(7-aminoheptanonyl-Phe-d-Trp-Lys-Thr[BZL]) (10 nM), a somatostatin antagonist. In conclusion, GABA enhances pancreatic exocrine secretion induced by secretagogues, which predominantly induce enzyme secretion, via GABAA receptors in the rat pancreas. The enhancing effect of GABA is partially mediated by inhibition of islet somatostatin release.

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Rau, Reina, et Andrew J. Darwin. « Identification of YsaP, the Pilotin of the Yersinia enterocolitica Ysa Type III Secretion System ». Journal of Bacteriology 197, n^o 17 (15 juin 2015) : 2770–79. http://dx.doi.org/10.1128/jb.00238-15.

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ABSTRACTSecretins are multimeric outer membrane pore-forming proteins found in complex export systems in Gram-negative bacteria. All type III secretion systems (T3SSs) have a secretin, and one of these is the YsaC secretin of the chromosomally encoded Ysa T3SS ofYersinia enterocolitica. In some cases, pilotin proteins, which are outer membrane lipoproteins, are required for their cognate secretins to multimerize and/or localize to the outer membrane. However, if secretin multimers mislocalize to the inner membrane, this can trigger the protective phage shock protein (Psp) stress response. During a screen for mutations that suppress YsaC toxicity to apspnull strain, we isolated several independent mutations predicted to increase expression of the YE3559 gene within the Ysa pathogenicity island. YE3559, which we have namedysaP, is predicted to encode a small outer membrane lipoprotein, and this location was confirmed by membrane fractionation. ElevatedysaPexpression increased the steady-state level of YsaC but made it less toxic to apspnull strain, and it also decreased YsaC-dependent induction ofpspgene expression. Subsequent experiments showed that YsaP was not required for YsaC multimerization but was required for the multimers to localize to the outer membrane. Consistent with this, aysaPnull mutation compromised protein export by the Ysa T3SS. All these observations suggest that YsaP is the pilotin for the YsaC secretin. This is only the second pilotin to be characterized forYersiniaand one of only a small number of pilotins described for all bacteria.IMPORTANCESecretins are essential for the virulence of many bacterial pathogens and also play roles in surface attachment, motility, and competence. This has generated considerable interest in understanding how secretins function. However, their fundamental differences from typical outer membrane proteins have raised various questions about secretins, including how they are assembled into outer membrane multimers. Pilotin proteins facilitate the assembly of some secretins, but only a small number of pilotins have been identified, slowing efforts to understand common and distinct features of secretin assembly. This study provides an important advance by identifying a novel member of the pilotin family and also demonstrating a method of pilotin discovery that could be broadly applied.

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Bitter, Wilbert, Ria van Boxtel, Mathijs Groeneweg, Patricia Sánchez Carballo, Ulrich Zähringer, Jan Tommassen et Margot Koster. « Species-Specific Functioning of the Pseudomonas XcpQ Secretin : Role for the C-Terminal Homology Domain and Lipopolysaccharide ». Journal of Bacteriology 189, n^o 8 (2 février 2007) : 2967–75. http://dx.doi.org/10.1128/jb.01583-06.

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ABSTRACT Secretins are oligomeric proteins that mediate the export of macromolecules across the bacterial outer membrane. The members of the secretin superfamily possess a C-terminal homology domain that is important for oligomerization and channel formation, while their N-terminal halves are thought to be involved in system-specific interactions. The XcpQ secretin of Pseudomonas spp. is a component of the type II secretion pathway. XcpQ from Pseudomonas alcaligenes is not able to functionally replace the secretin of the closely related species Pseudomonas aeruginosa. By analysis of chimeric XcpQ proteins, a region important for species-specific functioning was mapped between amino acid residues 344 and 478 in the C-terminal homology domain. Two chromosomal suppressor mutations were obtained that resulted in the proper functioning in P. aeruginosa of P. alcaligenes XcpQ and inactive hybrids. These mutations caused a defect in the synthesis of the lipopolysaccharide (LPS) outer core region. Subsequent analysis of different LPS mutants showed that changes in the outer core and not the loss of O antigen caused the suppressor phenotype. High concentrations of divalent cations in the growth medium also allowed P. alcaligenes XcpQ and inactive hybrids to function properly in P. aeruginosa. Since divalent cations are known to affect the structure of LPS, this observation supports the hypothesis that LPS has a role in the functioning of secretins.

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Solomon, Travis E., Gabor Varga, Ning Zeng, S. Vincent Wu, John H. Walsh et Joseph R. Reeve. « Different actions of secretin and Gly-extended secretin predict secretin receptor subtypes ». American Journal of Physiology-Gastrointestinal and Liver Physiology 280, n^o 1 (1 janvier 2001) : G88—G94. http://dx.doi.org/10.1152/ajpgi.2001.280.1.g88.

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Only one secretin receptor has been cloned and its properties characterized in native and transfected cells. To test the hypothesis that stimulatory and inhibitory effects of secretin are mediated by different secretin receptor subtypes, pancreatic and gastric secretory responses to secretin and secretin-Gly were determined in rats. Pancreatic fluid secretion was increased equipotently by secretin and secretin-Gly, but secretin was markedly more potent for inhibition of basal and gastrin-induced acid secretion. In Chinese hamster ovary cells stably transfected with the rat secretin receptor, secretin and secretin-Gly equipotently displaced125I-labeled secretin (IC50 values 5.3 ± 0.5 and 6.4 ± 0.6 nM, respectively). Secretin, but not secretin-Gly, caused release of somatostatin from rat gastric mucosal D cells. Thus the equipotent actions of secretin and secretin-Gly on pancreatic secretion appear to result from equal binding and activation of the pancreatic secretin receptor. Conversely, secretin more potently inhibited gastric acid secretion in vivo, and only secretin released somatostatin from D cells in vitro. These results support the existence of a secretin receptor subtype mediating inhibition of gastric acid secretion that is distinct from the previously characterized pancreatic secretin receptor.

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Matos, Esmeire Cruz, et Élder Antônio Sousa Paiva. « Structure, function and secretory products of the peltate glands of Centrolobium tomentosum (Fabaceae, Faboideae) ». Australian Journal of Botany 60, n^o 4 (2012) : 301. http://dx.doi.org/10.1071/bt12009.

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The glandular structures of Centrolobium tomentosum Guill. ex Benth. have been little studied despite the economic importance of this species. We describe here the distribution, development, structure and ultrastructure of the secretory cells of the peltate glands found on the vegetative organs of this species. Stem apices and leaves in various stages of development were collected and prepared for examination by light, scanning and transmission electron microscopy. Chemical analyses and conventional histochemical tests to determine the chemical nature of the secretory products were also carried out. Peltate glands occur on aerial vegetative organs during their primary growth stage. These trichomes are structurally stable, persisting throughout the development of the organ. During the initial stages of the gland development, cell separation creates a central space that expands as secretions accumulate. Maximum secretion rates occur during this phase and the secreting cells characteristically have well developed smooth and rough endoplasmic reticulum, and high numbers of plastids and mitochondria. During the later stages of the secretory phase, the central cells show symptoms of cell death and are incorporated in to the secretions. At trichome maturity, the central space is delimited by a uniseriate epithelium. In addition to the resin, which is the main secretory product, an extensive three-dimensional carbohydrate matrix was observed that extended throughout the central space, apparently giving support to the resin droplets. The terpenic nature of the secretion was confirmed by thin-layer chromatography. Given the terpenic nature of the secretion and the permanence of trichomes throughout all phases of leaf development, it is postulated that the resin-secreting trichomes act to protect the plant against herbivores.

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Olsen, Ole, Morten Wøjdemann, Belinda Berner, Gunvor Christiansen et Berit Sternby. « Secretin and Gastric Lipase Secretion ». Digestion 59, n^o 6 (1998) : 655–59. http://dx.doi.org/10.1159/000007571.

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Greco, A., R. Manna, G. Ghirlanda, L. Altomonte et A. Bertoli. « Does Secretin Control Insulin Secretion ? » Experimental and Clinical Endocrinology & ; Diabetes 84, n^o 04 (17 juillet 2009) : 81–86. http://dx.doi.org/10.1055/s-0029-1210369.

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Beglinger, C., E. Kohler, I. Whitehouse et K. Gyr. « Secretin and pancreatic enzyme secretion. » Gut 26, n^o 3 (1 mars 1985) : 320–22. http://dx.doi.org/10.1136/gut.26.3.320.

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Kim, C. D., P. Li, K. Y. Lee, D. H. Coy et W. Y. Chey. « Effect of [(CH2NH)4,5]secretin on pancreatic exocrine secretion in guinea pigs and rats ». American Journal of Physiology-Gastrointestinal and Liver Physiology 265, n^o 5 (1 novembre 1993) : G805—G810. http://dx.doi.org/10.1152/ajpgi.1993.265.5.g805.

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[psi 4,5]Secretin was shown to be a secretin receptor antagonist that inhibits secretin-stimulated increase in adenosine 3',5'-cyclic monophosphate in isolated pancreatic acini of the guinea pig. To determine whether it inhibits pancreatic exocrine secretion in vivo, we have studied the effect of [psi 4,5]secretin on the pancreatic secretion stimulated by secretin in anesthetized guinea pigs and rats. In basal state, [psi 4,5]secretin given intravenously for 2 or 3 h in varying doses of 1.6-32.7 nmol.kg-1.h-1 dose dependently increased pancreatic secretion of both fluid and bicarbonate during the 1st h, but it returned gradually to basal level within 2 or 3 h. On the other hand, [psi 4,5]secretin significantly inhibited the pancreatic secretion stimulated by either exogenous or endogenous secretin in a dose-related manner. The inhibitory effect of [psi 4,5]secretin in guinea pigs was greater than that in rats. However, it did not completely block the secretin-stimulated pancreatic secretion, whereas a rabbit antisecretin serum suppressed it completely. We conclude that 1) in the unstimulated state, [psi 4,5]secretin is a partial agonist of pancreatic exocrine secretion of both fluid and bicarbonate; and 2) when pancreatic secretion is stimulated by secretin, unlike an antisecretin serum, it is a partial inhibitor in intact guinea pigs and rats.

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Lazzaro, Mark D., et William W. Thomson. « Ultrastructural localization of calcium in the organic acid secreting trichomes of chickpea (Cicer arietinum) ». Canadian Journal of Botany 70, n^o 12 (1 décembre 1992) : 2319–25. http://dx.doi.org/10.1139/b92-290.

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In the organic acid secreting trichomes of chickpea (Cicer arietinum L.), calcium is localized in the stalk and head cells using pyroantimonate and X-ray microanalysis. Light calcium deposits are present in the endoplasmic reticulum, mitochondria, and cytoplasm of the stalk and head cells and in the cell walls of the stalk cells. Dense calcium deposits are present in the vacuoles of stalk and head cells and within the plasmodesmata between stalk cells. In the head cells, heavy calcium deposits are present in small, secretory vesicles that fuse with the plasma membrane. In addition, calcium deposits are localized in the cell wall space around the head cells, in the secretion chamber, and in collected secretions. These observations suggest that secretion from the head cells occurs predominantly through an exocytotic, vesicular pathway. We conclude that once secreted, calcium diffuses through the walls to the collecting chamber and subsequently through the cuticular pores into the secretion droplet. Key words: calcium secretion, Cicer arietinum, pyroantimonate, secretory vesicles, trichome.

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Clock, Sarah A., Paul J. Planet, Brenda A. Perez et David H. Figurski. « Outer Membrane Components of the Tad (Tight Adherence) Secreton of Aggregatibacter actinomycetemcomitans ». Journal of Bacteriology 190, n^o 3 (30 novembre 2007) : 980–90. http://dx.doi.org/10.1128/jb.01347-07.

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ABSTRACT Prokaryotic secretion relies on proteins that are widely conserved, including NTPases and secretins, and on proteins that are system specific. The Tad secretion system in Aggregatibacter actinomycetemcomitans is dedicated to the assembly and export of Flp pili, which are needed for tight adherence. Consistent with predictions that RcpA forms the multimeric outer membrane secretion channel (secretin) of the Flp pilus biogenesis apparatus, we observed the RcpA protein in multimers that were stable in the presence of detergent and found that rcpA and its closely related homologs form a novel and distinct subfamily within a well-supported gene phylogeny of the entire secretin gene superfamily. We also found that rcpA-like genes were always linked to Aggregatibacter rcpB- or Caulobacter cpaD-like genes. Using antisera, we determined the localization and gross abundances of conserved (RcpA and TadC) and unique (RcpB, RcpC, and TadD) Tad proteins. The three Rcp proteins (RcpA, RcpB, and RcpC) and TadD, a putative lipoprotein, localized to the bacterial outer membrane. RcpA, RcpC, and TadD were also found in the inner membrane, while TadC localized exclusively to the inner membrane. The RcpA secretin was necessary for wild-type abundances of RcpB and RcpC, and TadC was required for normal levels of all three Rcp proteins. TadC abundance defects were observed in rcpA and rcpC mutants. TadD production was essential for wild-type RcpA and RcpB abundances, and RcpA did not multimerize or localize to the outer membrane without the expression of TadD. These data indicate that membrane proteins TadC and TadD may influence the assembly, transport, and/or function of individual outer membrane Rcp proteins.

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Deng, Xiaoying, Dulce R. Guarita, Martha R. A. Pedroso, Christianna Kreiss, Paul G. Wood, Alan F. Sved et David C. Whitcomb. « PYY inhibits CCK-stimulated pancreatic secretion through the area postrema in unanesthetized rats ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 281, n^o 2 (1 août 2001) : R645—R653. http://dx.doi.org/10.1152/ajpregu.2001.281.2.r645.

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Peptide YY (PYY) inhibits CCK-8-secretin-stimulated pancreatic secretion in vivo. To investigate whether CCK-8-secretin-stimulated pancreatic secretion is mediated through a vago-vagal pathway and whether PYY inhibits this pathway through the area postrema (AP), chronic pancreatic, biliary, and duodenal catheters were implanted in AP-lesioned (APX) or sham-operated rats. The effects of APX on pancreatic secretion stimulated by bethanechol, pancreatic juice diversion (PJD), or CCK-8-secretin, were tested, with and without background PYY infusion, in unanesthetized rats. APX reduced basal pancreatic secretion by 15–20% ( P < 0.01). APX had no effect on bethanechol-stimulated secretion and potentiated protein secretion stimulated by PJD (396 vs. 284%) and exogenous CCK-8-secretin. In sham-operated rats, background PYY potently inhibited CCK-8-secretin-stimulated pancreatic fluid (1.8 vs. 48.2%) and protein secretion (3.7 vs. 45.8%) but potentiated fluid (52.9 vs. 43.1%) and protein (132.9 vs. 68.9%) secretion in APX rats. Our findings demonstrate that PYY inhibits CCK-8-secretin-stimulated pancreatic secretion through an AP-dependent mechanism in sham-operated rats. The AP also contributes to basal pancreatic secretion.

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Vignon, Guillaume, Rolf Köhler, Eric Larquet, Stéphanie Giroux, Marie-Christine Prévost, Pascal Roux et Anthony P. Pugsley. « Type IV-Like Pili Formed by the Type II Secreton : Specificity, Composition, Bundling, Polar Localization, and Surface Presentation of Peptides ». Journal of Bacteriology 185, n^o 11 (1 juin 2003) : 3416–28. http://dx.doi.org/10.1128/jb.185.11.3416-3428.2003.

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ABSTRACT The secreton or type II secretion machinery of gram-negative bacteria includes several type IV pilin-like proteins (the pseudopilins) that are absolutely required for secretion. We previously reported the presence of a bundled pilus composed of the pseudopilin PulG on the surface of agar-grown Escherichia coli K-12 cells expressing the Klebsiella oxytoca pullulanase (Pul) secreton genes at high levels (N. Sauvonnet, G. Vignon, A. P. Pugsley, and P. Gounon, EMBO J. 19:2221-2228, 2000). We show here that PulG is the only pseudopilin in purified pili and that the phenomenon is not restricted to the Pul secreton reconstituted in E. coli or to PulG. For example, high-level expression of the endogenous E. coli gsp secreton genes caused production of bundled pili composed of the pseudopilin GspG, and the Pul secreton was able to form pili composed of PulG-like proteins from secreton systems of other bacteria. PulG derivatives in which the C terminus was extended by the addition of eight different peptides were also assembled into pili and functioned in secretion. Three of the C-terminal peptides were shown to be exposed along the entire length of the assembled pili. Hence, the C terminus of PulG may represent a permissive site for the insertion of immunogenic epitopes or other peptide sequences. One of these PulG variants, with a six-histidine tag at its C terminus, formed nonpolar, nonbundled pili, suggesting that bundle formation and polar localization are not correlated with the ability of PulG to function in secretion. We propose that the PulG pilus is an artifactual manifestation of a periplasmic “pseudopilus” and that cycles of pseudopilus extension and retraction within the periplasm propel pullulanase through secretin channels in the outer membrane. Abnormally long pili that extend beyond the outer membrane are produced only when pilus length control and retraction are deregulated by overproduction of the major pseudopilus subunit (PulG).

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Blot-Chabaud, M., M. Dumont, M. Corbic et S. Erlinger. « Effect of acid-base balance on biliary bicarbonate secretion in the isolated perfused guinea pig liver ». American Journal of Physiology-Gastrointestinal and Liver Physiology 258, n^o 6 (1 juin 1990) : G863—G872. http://dx.doi.org/10.1152/ajpgi.1990.258.6.g863.

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Secretin-induced choleresis is of ductal origin and involves bicarbonate transport. Its mechanism is unknown. To determine the relative effects of systemic pH, PCO2, and bicarbonate concentration on secretin-stimulated bicarbonate transport, states of acute metabolic and respiratory acidosis or alkalosis were created in isolated perfused guinea pig livers with or without secretin infusion. During spontaneous secretion conditions, biliary bicarbonate secretion was not correlated with perfusate pH (7.19-7.62) or perfusate PCO2 (23.9-59.7) but was significantly correlated with perfusate bicarbonate concentration (17.5-37.9 mM). Under secretion infusion (25 mU/min), bile flow and biliary bicarbonate concentration increased significantly (109 and 51%, respectively). Biliary bicarbonate secretion was not correlated with perfusate pH (7.19-7.60) but was significantly correlated both with perfusate bicarbonate concentration (14.6-36.8 mM) and PCO2 (25.8-54.3 mmHg). Spontaneous and secretin-induced bile flow were correlated with biliary bicarbonate concentration. The correlation between biliary bicarbonate secretion and PCO2 during secretin-induced choleresis supports the hypothesis that secretin-induced biliary bicarbonate secretion could, at least in part, involve a transport of H+ (or OH-) rather than HCO3- itself and that intracellular pH could play a role in the regulation of this secretion. Amiloride (5 X 10(-4) M) did not influence secretin-induced biliary bicarbonate secretion. This result suggests that the Na(+)-H+ exchange is not involved in bicarbonate secretion by ductular cells.

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Caligiuri, Alessandra, Shannon Glaser, Rebecca E. Rodgers, Jo Lynne Phinizy, Willie Robertson, Emanuela Papa, Massimo Pinzani et Gianfranco Alpini. « Endothelin-1 inhibits secretin-stimulated ductal secretion by interacting with ETA receptors on large cholangiocytes ». American Journal of Physiology-Gastrointestinal and Liver Physiology 275, n^o 4 (1 octobre 1998) : G835—G846. http://dx.doi.org/10.1152/ajpgi.1998.275.4.g835.

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We studied the expression of endothelin-1 (ET-1) receptors (ETA and ETB) and the effects of ET-1 on cholangiocyte secretion. The effects of ET-1 on cholangiocyte secretion were assessed in normal and bile duct-ligated (BDL) rats by measuring 1) basal and secretin-induced choleresis in vivo, 2) secretin receptor gene expression and cAMP levels in small and large cholangiocytes, and 3) luminal expansion in response to secretin in intrahepatic bile duct units (IBDU). ETA and ETB receptors were expressed by small and large cholangiocytes. ET-1 had no effect on basal bile flow or bicarbonate secretion in normal or BDL rats but decreased secretin-induced bicarbonate-rich choleresis in BDL rats. ET-1 decreased secretin receptor gene expression and secretin-stimulated cAMP synthesis in large cholangiocytes and secretin-induced luminal expansion in IBDU from normal or BDL rats. The inhibitory effects of ET-1 on secretin-induced cAMP synthesis and luminal duct expansion were blocked by specific inhibitors of the ETA (BQ-610) receptor. ET-1 inhibits secretin-induced ductal secretion by decreasing secretin receptor and cAMP synthesis, two important determinants of ductal secretion.

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Burghout, Peter, Ria van Boxtel, Patrick Van Gelder, Philippe Ringler, Shirley A. Müller, Jan Tommassen et Margot Koster. « Structure and Electrophysiological Properties of the YscC Secretin from the Type III Secretion System of Yersinia enterocolitica ». Journal of Bacteriology 186, n^o 14 (15 juillet 2004) : 4645–54. http://dx.doi.org/10.1128/jb.186.14.4645-4654.2004.

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ABSTRACT YscC is the integral outer membrane component of the type III protein secretion machinery of Yersinia enterocolitica and belongs to the family of secretins. This group of proteins forms stable ring-like oligomers in the outer membrane, which are thought to function as transport channels for macromolecules. The YscC oligomer was purified after solubilization from the membrane with a nonionic detergent. Sodium dodecyl sulfate did not dissociate the oligomer, but it caused a change in electrophoretic mobility and an increase in protease susceptibility, indicating partial denaturation of the subunits within the oligomer. The mass of the homo-oligomer, as determined by scanning transmission electron microscopy, was approximately 1 MDa. Analysis of the angular power spectrum from averaged top views of negatively stained YscC oligomers revealed a 13-fold angular order, suggesting that the oligomer consists of 13 subunits. Reconstituted in planar lipid bilayers, the YscC oligomer displayed a constant voltage-independent conductance of approximately 3 nS, thus forming a stable pore. However, in vivo, the expression of YscC did not lead to an increased permeability of the outer membrane. Electron microscopy revealed that the YscC oligomer is composed of three domains, two stacked rings attached to a conical domain. This structure is consistent with the notion that the secretin forms the upper part of the basal body of the needle structure of the type III secreton.

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Li, James P., Ta-Min Chang et William Y. Chey. « Roles of 5-HT receptors in the release and action of secretin on pancreatic secretion in rats ». American Journal of Physiology-Gastrointestinal and Liver Physiology 280, n^o 4 (1 avril 2001) : G595—G602. http://dx.doi.org/10.1152/ajpgi.2001.280.4.g595.

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5-Hydroxytryptamine (serotonin, 5-HT) is a hormone and neurotransmitter regulating gastrointestinal functions. 5-HT receptors are widely distributed in gastrointestinal mucosa and the enteric nervous system. Duodenal acidification stimulates not only the release of both 5-HT and secretin but also pancreatic exocrine secretion. We investigated the effect of 5-HT receptor antagonists on the release of secretin and pancreatic secretion of water and bicarbonate induced by duodenal acidification in anesthetized rats. Both the 5-HT2 receptor antagonist ketanserin and the 5-HT3 receptor antagonist ondansetron at 1–100 μg/kg dose-dependently inhibited acid-induced increases in plasma secretin concentration and pancreatic exocrine secretion. Neither the 5-HT1 receptor antagonists pindolol and 5-HTP-DP nor the 5-HT4 receptor antagonist SDZ-205,557 affected acid-evoked release of secretin or pancreatic secretion. None of the 5-HT receptor antagonists affected basal pancreatic secretion or plasma secretin concentration. Ketanserin or ondansetron at 10 μg/kg or a combination of both suppressed the pancreatic secretion in response to intravenous secretin at 2.5 and 5 pmol · kg−1 · h−1 by 55–75%, but not at 10 pmol · kg−1 · h−1. Atropine (50 μg/kg) significantly attenuated the inhibitory effect of ketanserin on pancreatic secretion but not on the release of secretin. These observations suggest that 5-HT2 and 5-HT3receptors mediate duodenal acidification-induced release of secretin and pancreatic secretion of fluid and bicarbonate. Also, regulation of pancreatic exocrine secretion through 5-HT2 receptors may involve a cholinergic pathway in the rat.

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Tam, Janice K. V., Leo T. O. Lee, Jun Jin et Billy K. C. Chow. « MOLECULAR EVOLUTION OF GPCRS : Secretin/secretin receptors ». Journal of Molecular Endocrinology 52, n^o 3 (juin 2014) : T1—T14. http://dx.doi.org/10.1530/jme-13-0259.

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In mammals, secretin is a 27-amino acid peptide that was first studied in 1902 by Bayliss and Starling from the extracts of the jejunal mucosa for its ability to stimulate pancreatic secretion. To date, secretin has only been identified in tetrapods, with the earliest diverged secretin found in frogs. Despite being the first hormone discovered, secretin's evolutionary origin remains enigmatic, it shows moderate sequence identity in nonmammalian tetrapods but is highly conserved in mammals. Current hypotheses suggest that although secretin has already emerged before the divergence of osteichthyans, it was lost in fish and retained only in land vertebrates. Nevertheless, the cognate receptor of secretin has been identified in both actinopterygian fish (zebrafish) and sarcopterygian fish (lungfish). However, the zebrafish secretin receptor was shown to be nonbioactive. Based on the present information that the earliest diverged bioactive secretin receptor was found in lungfish, and its ability to interact with both vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide potently suggested that secretin receptor was descended from a VPAC-like receptor gene before the Actinopterygii–Sarcopterygii split in the vertebrate lineage. Hence, secretin and secretin receptor have gone through independent evolutionary trajectories despite their concurrent emergence post-2R. A functional secretin–secretin receptor axis has probably emerged in the amphibians. Although the pleiotropic actions of secretin are well documented in the literature, only limited information of its physiological functions in nonmammalian tetrapods have been reported. To decipher the structural and functional divergence of secretin and secretin receptor, functional characterization of the ligand–receptor pair in nonmammals would be the next perspective for investigation.

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Song, Y., P. Li, K. Y. Lee, T. M. Chang et W. Y. Chey. « Canine pancreatic juice stimulates the release of secretin and pancreatic secretion in the dog ». American Journal of Physiology-Gastrointestinal and Liver Physiology 277, n^o 3 (1 septembre 1999) : G731—G735. http://dx.doi.org/10.1152/ajpgi.1999.277.3.g731.

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A secretin-releasing factor (SRF) was found in canine pancreatic juice that increases plasma secretin and stimulates pancreatic secretion in rats, suggesting that a positive feedback mechanism may be involved in the regulation of pancreatic secretion. In the present study, we investigated to determine whether or not SRF releases endogenous secretin and stimulates exocrine pancreatic secretion in conscious dogs. Fresh pancreatic juice was collected from four dogs by intravenous administration of secretin at 0.5 μg ⋅ kg−1 ⋅ h−1and CCK at 0.2 μg ⋅ kg−1 ⋅ h. The juice was boiled for 10 min at 100°C. Experiments were carried out in phase I of spontaneous cycle of interdigestive pancreatic secretion. The testing solutions were infused intraduodenally in separate experiments: NaHCO3solution (0.1 M, 4.5 ml/min, 60 min), a corn oil (Lipomul, 2 ml/min, 10 min), boiled pancreatic juice (BPJ, 4.5 ml/min, 60 min), and mixture of BPJ and Lipomul. Pancreatic secretion of fluid and bicarbonate was significantly increased by either BPJ or a mixture of BPJ and Lipomul (34- and 31-fold or 41- and 38-fold, respectively). Plasma secretin level also significantly increased by 164.7 ± 13.4% and 223.1 ± 35.0%, respectively, from basal concentration of 1.7 ± 0.5 pM. In contrast, neither bicarbonate solution nor Lipomul influenced the plasma secretin level or pancreatic secretion. In addition, when Lipomul was incubated with BPJ, no fatty acid was produced. Thus the increased pancreatic secretion in the dog infused with a combination of BPJ and Lipomul was caused by SRF in BPJ, which released endogenous secretin. Moreover, the increases by BPJ of both plasma secretin level and bicarbonate secretion were completely blocked by intravenous administration of an antisecretin antibody in these dogs. The observations suggest that SRF in pancreatic juice exerts a positive feedback effect on exocrine pancreatic secretion that is mediated by the release of secretin in the interdigestive state in dogs.

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Tetsi Nomigni, Milène, Sophie Ouzounian, Alice Benoit, Jacqueline Vadrot, Frédérique Tissier, Sylvie Renouf, Hervé Lefebvre, Sophie Christin-Maitre et Estelle Louiset. « Steroidogenic enzyme profile in an androgen-secreting adrenocortical oncocytoma associated with hirsustism ». Endocrine Connections 4, n^o 2 (juin 2015) : 117–27. http://dx.doi.org/10.1530/ec-15-0014.

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Hirsutism induced by hyperandrogenism can be associated with polycystic ovary syndrome, 21-hydroxylase (OH) deficiency or androgen-secreting tumors, including ovarian and adrenal tumors. Adrenal androgen-secreting tumors are frequently malignant. Adrenal oncocytomas represent rare causes of hyperandrogenism. The aim of the study was to investigate steroidogenic enzyme expression and steroid secretion in an androgen-secreting adrenal oncocytoma in a young woman presenting with hirsutism. Hyperandrogenism was diagnosed on the basis of elevated plasma Δ4-androstenedione and testosterone levels. Pelvic ultrasound was normal, CT scanning revealed a right adrenal mass. Androgens were assessed in adrenal and ovarian vein samples and proved a right adrenal origin. Adrenalectomy normalized androgen levels and the adrenal tumor was diagnosed as an oncocytoma. Real time-PCR, immunohistochemistry and cell culture studies were performed on tumor explants to investigate the steroid secretion profile. Among enzymes required for cortisol synthesis, 17α-OH and 3β-hydroxysteroid dehydrogenase 2 (3β-HSD2) were highly expressed whereas 21-OH and 11β-OH were weakly produced at the mRNA and/or protein levels. Enzymes involved in testosterone production, 17β-HSD5 and 17β-HSD3, were also detected. ACTH receptor was present in the tissue. Cortisol, Δ4-androstenedione and testosterone secretions by cultured cells were increased by ACTH. These results provide the first demonstration, to our knowledge, of abnormal expression profile of steroidogenic enzymes in an adrenocortical oncocytoma. Our results also indicate that Δ4-androstenedione hypersecretion resulted from high 17α-OH and 3β-HSD2 expression in combination with low expression of 21-OH and 11β-OH. Testosterone production was ascribed to occurrence of 17β-HSD5 and 17β-HSD3. Finally, our results indicate that androgen secretion was stimulated by ACTH.

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Giusti, Francesca, Federica Cioppi, Caterina Fossi, Francesca Marini, Laura Masi, Francesco Tonelli et Maria Luisa Brandi. « Secretin Stimulation Test and Early Diagnosis of Gastrinoma in MEN1 Syndrome : Survey on the MEN1 Florentine Database ». Journal of Clinical Endocrinology & ; Metabolism 107, n^o 5 (18 décembre 2021) : e2110-e2123. http://dx.doi.org/10.1210/clinem/dgab903.

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Abstract Context Multiple endocrine neoplasia type 1 (MEN1) is a rare inherited endocrine cancer syndrome. Multiple gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs) affect 30% to 80% of MEN1 patients, with the most common functioning GEP-NET being gastrinoma. Biochemical identification of hypergastrinemia may help to recognize the presence of gastrinomas before they are detectable by instrumental screening, enabling early diagnosis and start of therapy, preferably before tumor progression and metastases occurrence. Objective Evaluate the effectiveness of secretin stimulation test to precociously diagnose the presence of gastrin-secreting tumors. Design Results of secretin stimulation tests, performed between 1991 and February 2020, were retrospectively analyzed, as aggregate, in a cohort of MEN1 patients with GEP-NETs. Setting Data were extracted from the MEN1 Florentine database. Patients The study included 72 MEN1 patients with GEP-NETs who underwent a secretin stimulation test for the evaluation of gastrin secretion. Outcomes A positive secretin stimulation test was assumed with a difference between basal fasting serum gastrin (FSG) and the maximum stimulated value of gastrin over 120 pg/mL. Results The secretin stimulation test showed a secretin-induced hypergastrinemia in 27.8% (20/72) of patients with GEP-NETs, and a positive test in 18 cases. The test allowed the identification of a positively stimulated hypergastrinemia in 75.0% (3/4) of patients who presented a basal FSG within the normal range. Conclusions Diagnosis of gastrinoma is complex, difficult, and controversial. Results of this study confirm that a positive secretin stimulation test allows early diagnosis of gastrinomas, even in the presence of borderline or normal levels of nonstimulated FSG.

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Fiorucci, Stefano, Eleonora Distrutti, Barbara Federici, Barbara Palazzetti, Monia Baldoni, Antonio Morelli et Giuseppe Cirino. « PAR-2 modulates pepsinogen secretion from gastric-isolated chief cells ». American Journal of Physiology-Gastrointestinal and Liver Physiology 285, n^o 3 (septembre 2003) : G611—G620. http://dx.doi.org/10.1152/ajpgi.00388.2002.

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In the present study, we investigated whether activation of protease-activated receptor type 2 (PAR-2) with SLIGRL (SL)NH2, a short mimetic agonistic peptide, directly stimulates pepsinogen secretion from gastric-isolated, pepsinogen-secreting (chief) cells. Immunostaining of gastric-dispersed chief cells with a specific anti-PAR-2 antibody demonstrated expression of PAR-2 receptors on membrane and cytoplasm. SL-NH2 and trypsin potently stimulated pepsinogen secretion (EC50 = 0.3 nM) and caused Ca2+ mobilization (EC50 = 0.6 nM). In contrast to SL-NH2, the scramble peptide LSIGRL-NH2 failed to stimulate pepsinogen release. Exposure to SL-NH2 also resulted in ERK1/2 phosphorylation and activation. Exposure of chief cells to phosphotyrosine kinase inhibitors and 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one, a selective MEK inhibitor, significantly reduced secretion induced by SL-NH2. Pepsinogen secretion induced by SL-NH2 was desensitized by pretreating the cells with the mimetic peptide and trypsin, and exposure to SL-NH2 abrogates pepsinogen secretion induced by carbachol and CCK-8, but not secretion induced by secretin and vasointestinal peptide. Exposure to Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2 (substance P) but not to calcitonin gene-related peptide increased pepsinogen release. The neurokinin-1 receptor antagonist, N-acetyl-l-tryptophan 3,5-bis(trifluoromethyl)benzyl ester, inhibited substance P-stimulated pepsinogen secretion, whereas it did not affect secretion induced by SL-NH2. Collectively, these data indicate that PAR-2 is expressed on gastric chief cells and that its activation causes a Ca2+-ERK-dependent stimulation of pepsinogen secretion.

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Sutliff, V. E., J. P. Raufman, R. T. Jensen et J. D. Gardner. « Actions of vasoactive intestinal peptide and secretin on chief cells prepared from guinea pig stomach ». American Journal of Physiology-Gastrointestinal and Liver Physiology 251, n^o 1 (1 juillet 1986) : G96—G102. http://dx.doi.org/10.1152/ajpgi.1986.251.1.g96.

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Vasoactive intestinal peptide and secretin increased cellular cAMP and pepsinogen secretion in dispersed chief cells from guinea pig gastric mucosa. With each peptide there was a close correlation between the dose-response curve for changes in cellular cAMP and that for changes in pepsinogen secretion. Vasoactive intestinal peptide-(10–28) and secretin-(5–27) had no agonist activity and antagonized the actions of vasoactive intestinal peptide and secretin on cellular cAMP and pepsinogen secretion. Studies of binding of 125I-vasoactive intestinal peptide and of 125I-secretin indicated that gastric chief cells possess four classes of binding sites for vasoactive intestinal peptide and secretin and that occupation of two of these classes of binding sites correlates with the abilities of vasoactive intestinal peptide and secretin to increase cellular cAMP and pepsinogen secretion. What function, if any, is mediated by occupation by the other two classes of binding sites remains to be determined.

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Kanno, Noriatsu, Gene LeSage, Shannon Glaser et Gianfranco Alpini. « Regulation of cholangiocyte bicarbonate secretion ». American Journal of Physiology-Gastrointestinal and Liver Physiology 281, n^o 3 (1 septembre 2001) : G612—G625. http://dx.doi.org/10.1152/ajpgi.2001.281.3.g612.

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The objective of this review article is to discuss the role of secretin and its receptor in the regulation of the secretory activity of intrahepatic bile duct epithelial cells (i.e., cholangiocytes). After a brief overview of cholangiocyte functions, we provide an historical background for the role of secretin and its receptor in the regulation of ductal secretion. We review the newly developed experimental in vivo and in vitro tools, which lead to understanding of the mechanisms of secretin regulation of cholangiocyte functions. After a description of the intracellular mechanisms by which secretin stimulates ductal secretion, we discuss the heterogeneous responses of different-sized intrahepatic bile ducts to gastrointestinal hormones. Furthermore, we outline the role of a number of cooperative factors (e.g., nerves, alkaline phosphatase, gastrointestinal hormones, neuropeptides, and bile acids) in the regulation of secretin-stimulated ductal secretion. Finally, we discuss other factors that may also play an important role in the regulation of secretin-stimulated ductal secretion.

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Possot, Odile M., Manon Gérard-Vincent et Anthony P. Pugsley. « Membrane Association and Multimerization of Secreton Component PulC ». Journal of Bacteriology 181, n^o 13 (1 juillet 1999) : 4004–11. http://dx.doi.org/10.1128/jb.181.13.4004-4011.1999.

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ABSTRACT The PulC component of the Klebsiella oxytocapullulanase secretion machinery (the secreton) was found by subcellular fractionation to be associated with both the cytoplasmic (inner) and outer membranes. Association with the outer membrane was independent of other secreton components, including the outer membrane protein PulD (secretin). The association of PulC with the inner membrane is mediated by the signal anchor sequence located close to its N terminus. These results suggest that PulC forms a bridge between the two membranes that is disrupted when bacteria are broken open for fractionation. Neither the signal anchor sequence nor the cytoplasmic N-terminal region that precedes it was found to be required for PulC function, indicating that PulC does not undergo sequence-specific interactions with other cytoplasmic membrane proteins. Cross-linking of whole cells resulted in the formation of a ca. 110-kDa band that reacted with PulC-specific serum and whose detection depended on the presence of PulD. However, antibodies against PulD failed to react with this band, suggesting that it could be a homo-PulC trimer whose formation requires PulD. The data are discussed in terms of the possible role of PulC in energy transduction for exoprotein secretion.

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Ko, S. B. H., S. Naruse, M. Kitagawa, H. Ishiguro, M. Murakami et T. Hayakawa. « Arginine vasopressin inhibits fluid secretion in guinea pig pancreatic duct cells ». American Journal of Physiology-Gastrointestinal and Liver Physiology 277, n^o 1 (1 juillet 1999) : G48—G54. http://dx.doi.org/10.1152/ajpgi.1999.277.1.g48.

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The effects of arginine vasopressin (AVP) on pancreatic ductal secretion were studied in guinea pigs. In the isolated vascularly perfused pancreas, AVP reduced secretin-stimulated fluid secretion and increased the vascular resistance when the perfusion rate was held constant. In the isolated interlobular duct segments, AVP inhibited secretin-stimulated fluid secretion, indicating the direct inhibitory action of AVP on the duct cells. AVP affected neither the basal nor the secretin-induced cAMP productions, suggesting that AVP inhibits the fluid secretion at a point distal to the production of cAMP. AVP increased intracellular Ca2+ concentration ([Ca2+]i) in the absence of extracellular Ca2+. When [Ca2+]iwas elevated by the application of thapsigargin, AVP caused a rapid decrease in [Ca2+]i. AVP seems to activate both Ca2+release from intracellular stores and Ca2+ efflux across the plasma membrane, but its relation to the inhibition of fluid secretion remains to be clarified. It is concluded that AVP directly inhibits secretin-stimulated ductal fluid secretion in the guinea pig pancreas.

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Westholm, Efraim, Anna Wendt et Lena Eliasson. « Islet Function in the Pathogenesis of Cystic Fibrosis-Related Diabetes Mellitus ». Clinical Medicine Insights : Endocrinology and Diabetes 14 (janvier 2021) : 117955142110312. http://dx.doi.org/10.1177/11795514211031204.

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Cystic fibrosis-related diabetes mellitus (CFRD) is the most common non-pulmonary co-morbidity in cystic fibrosis (CF). CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene ( CFTR), which leads to aberrant luminal fluid secretions in organs such as the lungs and pancreas. How dysfunctional CFTR leads to CFRD is still under debate. Both intrinsic effects of dysfunctional CFTR in hormone secreting cells of the islets and effects of exocrine damage have been proposed. In the current review, we discuss these non-mutually exclusive hypotheses with a special focus on how dysfunctional CFTR in endocrine cells may contribute to an altered glucose homeostasis. We outline the proposed role of CFTR in the molecular pathways of β-cell insulin secretion and α-cell glucagon secretion, and touch upon the importance of the exocrine pancreas and intra-pancreatic crosstalk for proper islet function.

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Francis, Heather, Gene LeSage, Sharon DeMorrow, Domenico Alvaro, Yoshiyuki Ueno, Julie Venter, Shannon Glaser et al. « The α2-adrenergic receptor agonist UK 14,304 inhibits secretin-stimulated ductal secretion by downregulation of the cAMP system in bile duct-ligated rats ». American Journal of Physiology-Cell Physiology 293, n^o 4 (octobre 2007) : C1252—C1262. http://dx.doi.org/10.1152/ajpcell.00031.2007.

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Secretin stimulates ductal secretion by activation of cAMP → PKA → CFTR → Cl−/HCO3− exchanger in cholangiocytes. We evaluated the expression of α2A-, α2B-, and α2C-adrenergic receptors in cholangiocytes and the effects of the selective α2-adrenergic agonist UK 14,304, on basal and secretin-stimulated ductal secretion. In normal rats, we evaluated the effect of UK 14,304 on bile and bicarbonate secretion. In bile duct-ligated (BDL) rats, we evaluated the effect of UK 14,304 on basal and secretin-stimulated 1) bile and bicarbonate secretion; 2) duct secretion in intrahepatic bile duct units (IBDU) in the absence or presence of 5-( N-ethyl- N-isopropyl)amiloride (EIPA), an inhibitor of the Na+/H+ exchanger isoform NHE3; and 3) cAMP levels, PKA activity, Cl− efflux, and Cl−/HCO3− exchanger activity in purified cholangiocytes. α2-Adrenergic receptors were expressed by all cholangiocytes in normal and BDL liver sections. UK 14,304 did not change bile and bicarbonate secretion of normal rats. In BDL rats, UK 14,304 inhibited secretin-stimulated 1) bile and bicarbonate secretion, 2) expansion of IBDU luminal spaces, and 3) cAMP levels, PKA activity, Cl− efflux, and Cl−/HCO3− exchanger activity in cholangiocytes. There was decreased lumen size after removal of secretin in IBDU pretreated with UK 14,304. In IBDU pretreated with EIPA, there was no significant decrease in luminal space after removal of secretin in either the absence or presence of UK 14,304. The inhibitory effect of UK 14,304 on ductal secretion is not mediated by the apical cholangiocyte NHE3. α2-Adrenergic receptors play a role in counterregulating enhanced ductal secretion associated with cholangiocyte proliferation in chronic cholestatic liver diseases.

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Miyamoto, S., M. Irahara, K. Ushigoe, A. Kuwahara, H. Sugino et T. Aono. « Effects of activin on hormone secretion by single female rat pituitary cells : analysis by cell immunoblot assay ». Journal of Endocrinology 161, n^o 3 (1 juin 1999) : 375–82. http://dx.doi.org/10.1677/joe.0.1610375.

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We investigated the effect of activin A on secretion of LH, FSH, and prolactin (PRL) by female cultured rat pituitary cells at the single-cell level by means of the cell immunoblot assay. Anterior pituitary cells from 8-week-old female rats were preincubated with or without activin A for 24 h, after which they were monodispersed and immediately used for cell immunoblot assay. The percentages of LH-, FSH- and PRL-immunoreactive cell blots detected were 5.5, 5.3 and 43.1%, respectively, of all pituitary cells applied to the transfer membrane. The percentage of LH-secreting cells and mean LH secretion per cell did not change after treatment with activin. In contrast, activin significantly increased the percentage of FSH-secreting cells and mean FSH secretion per cell to 136.0 and 114. 5% respectively. In addition, activin significantly decreased the percentage of PRL-secreting cells and mean PRL secretion per cell to 52.2 and 72.0% respectively. These results suggest that (1) activin A has effects on female rat pituitary cells that increase not only the amount of FSH secretion per cell but also the number of FSH-secreting cells, and (2) activin A decreases both the amount of PRL secretion per cell and the number of PRL-secreting cells.

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Li, P., T. M. Chang et W. Y. Chey. « Secretin inhibits gastric acid secretion via a vagal afferent pathway in rats ». American Journal of Physiology-Gastrointestinal and Liver Physiology 275, n^o 1 (1 juillet 1998) : G22—G28. http://dx.doi.org/10.1152/ajpgi.1998.275.1.g22.

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Secretin is an enterogastrone that inhibits gastric acid secretion and motility. Recently, it was reported that secretin inhibited gastric emptying via a capsaicin (Cap)-sensitive vagal afferent pathway. However, a possible role of the sensory afferent pathway in secretin-inhibited acid secretion has not been clarified. We investigated whether or not the acid secretion suppressed by secretin is modulated by a vagal and/or splanchnic afferent pathway in rats. Subdiaphragmatic perivagal (PV) or periceliac ganglionic (PCG) application of Cap (10 mg/ml) or vehicle was performed in both conscious and anesthetized rats 2 wk before experiments. Bilateral vagotomy was performed in some conscious rats 5 days before studies. Pentagastrin was administered intravenously at 0.6 μg ⋅ kg−1 ⋅ h−1. Secretin (20 pmol ⋅ kg−1 ⋅ h−1iv) or 0.03 N HCl (4.32 ml/h id) was infused in conscious rats with gastric cannulas or anesthetized rats with ligation of the pylorus, respectively. A rabbit antisecretin serum was injected in some anesthetized rats before duodenal acidification. Secretin significantly inhibited pentagastrin-stimulated acid secretion by 63% ( P < 0.01), which was abolished by both vagotomy and PV treatment of Cap in conscious rats. In anesthetized rats, duodenal infusion of 0.03 N HCl suppressed pentagastrin-induced acid secretion by 59.4% ( P < 0.01), which was reversed not only by antisecretin serum but also by PV application of Cap. However, PCG treatment with Cap did not influence the inhibition by secretin or duodenal acidification in either awake or anesthetized rats. These results indicate that the inhibition by secretin of pentagastrin-stimulated acid secretion is mediated by a Cap-sensitive vagal afferent pathway but not via a splanchnic afferent pathway in rats.

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Glaser, Shannon S., Rebecca E. D. Rodgers, Jo Lynne Phinizy, Willie E. Robertson, John Lasater, Alessandra Caligiuri, Ziga Tretjak, Gene D. Lesage et Gianfranco Alpini. « Gastrin inhibits secretin-induced ductal secretion by interaction with specific receptors on rat cholangiocytes ». American Journal of Physiology-Gastrointestinal and Liver Physiology 273, n^o 5 (1 novembre 1997) : G1061—G1070. http://dx.doi.org/10.1152/ajpgi.1997.273.5.g1061.

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We assessed the effect of gastrin on ductal secretion in normal and bile duct-ligated (BDL) rats. The effect of gastrin on ductal secretion was examined in the presence of proglumide, a specific antagonist for gastrin receptor (GR). We isolated pure cholangiocytes from normal and BDL rats and assessed gastrin effects on secretin receptor (SR) gene expression and intracellular adenosine 3′,5′-cyclic monophosphate (cAMP) levels. We examined the presence of GR mRNA in cholangiocytes by reverse transcription polymerase chain reaction (RT-PCR). In normal or BDL rats, gastrin produced no changes in spontaneous bile secretion. Simultaneous infusion of gastrin inhibited secretin-induced choleresis and bicarbonate output in BDL rats. In the presence of proglumide gastrin did not inhibit secretin-induced choleresis in BDL rats. Gastrin decreased in cholangiocytes from BDL rats 1) SR gene expression and 2) secretin-induced cAMP levels. With the use of RT-PCR, GR mRNA was detected in cholangiocytes. Similar to what is shown for secretin and somatostatin, we propose that the opposing effects of secretin and gastrin on cholangiocyte secretory activity regulate ductal secretion in rats.

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Alvaro, D., A. Mennone et J. L. Boyer. « Role of kinases and phosphatases in the regulation of fluid secretion and Cl-/HCO3- exchange in cholangiocytes ». American Journal of Physiology-Gastrointestinal and Liver Physiology 273, n^o 2 (1 août 1997) : G303—G313. http://dx.doi.org/10.1152/ajpgi.1997.273.2.g303.

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The role of protein kinase A (PKA), protein kinase C (PKC), and protein phosphatases in the process of secretin stimulation of fluid and bicarbonate secretion from biliary epithelium was examined using a novel isolated bile duct unit (IBDU) model from rat liver. Sp-adenosine 3',5'-cyclic monophosphothiolate (Sp-cAMPS), 100 microM, a PKA-specific agonist, significantly increased secretion during a 30-min perfusion (+61%, P < 0.01). In contrast, preincubation and perfusion of Rp-cAMPS, 100 microM, a specific PKA inhibitor, reduced the ability of secretin to stimulate both fluid secretion (111 vs. 25%; P < 0.01) and Cl-/HCO3- exchanger activity (80 vs. 28%). Neither the PKC agonist phorbol 12-myristate 13-acetate, 10 microM, nor the PKC antagonist staurosporine showed any effect on either basal or secretin-stimulated fluid secretion or Cl-/HCO3- exchange activity in IBDU. Okadaic acid, a specific inhibitor of protein phosphatases 1 and 2A, also had no effect on basal fluid secretion or on the basal activity of the Cl-/HCO3- exchanger. However, okadaic acid resulted in persistence of secretion after removal of secretin, in contrast to the reduction in secretion observed in controls. These findings indicate that PKA but not PKC is involved in the signal transduction of secretin-stimulated fluid secretion and Cl-/HCO3- exchange activity in rat bile duct epithelium, a process inactivated by dephosphorylation by protein phosphatases 1 and/or 2A.

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Giraud, Olivier, Serge Molliex, Corinne Rolland, Véronique Leçon-Malas, Jean-Marie Desmonts, Michel Aubier et Monique Dehoux. « Halogenated Anesthetics Reduce Interleukin-1β-induced Cytokine Secretion by Rat Alveolar Type II Cells in Primary Culture ». Anesthesiology 98, n^o 1 (1 janvier 2003) : 74–81. http://dx.doi.org/10.1097/00000542-200301000-00015.

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Background Alveolar epithelial type II (AT II ) cells participate in the intraalveolar cytokine network by secreting cytokines and are widely exposed to volatile anesthetics during general anesthesia. The aim of the current study was to evaluate the effects of halothane, enflurane, and isoflurane on rat AT II cell cytokine secretions in AT II primary cell cultures. Methods Alveolar epithelial type II primary cell cultures were obtained from adult rat lungs. AT II cells were stimulated by recombinant murine interleukin-1beta (rmIL-1beta) to mimic an inflammatory response, and immediately exposed for various duration to different concentration of halothane, enflurane, or isoflurane. Interleukin-6, macrophage inflammatory protein-2 (MIP-2), and monocyte chemoattractant protein-1 (MCP-1) protein concentrations were then measured in cell culture supernatants. Recombinant mIL-1beta-stimulated AT II cells exposed to air served as control. Results Halothane, isoflurane, and enflurane (1 minimum alveolar concentration [MAC], 4 h) decreased rmIL-1beta-stimulated AT II cell secretions of interleukin-6, MIP-2, and MCP-1, but did not modify total protein secretion. Halothane exposure decreased rmIL-1beta-stimulated AT II cell secretions of interleukin-6, MIP-2, and MCP-1 in a dose- and time-dependent manner. Total protein concentrations remained unchanged except AT II 1.5 MAC of halothane, and no cytotoxic effect could be evidenced by lactate dehydrogenase release. These effects were transient as rmIL-1beta-stimulated AT II cell secretions of interleukin-6 and MIP-2 progressively reached control values between 4 and 24 h after the end of halothane exposure. However, MCP-1 inhibition persisted until 24 h. rmIL-1beta-induced MIP-2 and tumor necrosis factor-alpha mRNA expression were decreased by 36 and 24%, respectively, after halothane exposure. Conclusions The current study shows that exposure of rmIL-1beta-stimulated AT II cells to volatile anesthetics reversibly alters their cytokine secretion. Therefore, volatile anesthesia, by modulating pulmonary epithelial cell secretion of inflammatory cytokines, might affect the lung inflammatory response.

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Burkhardt, Janin, Janet Vonck et Beate Averhoff. « Structure and Function of PilQ, a Secretin of the DNA Transporter from the Thermophilic Bacterium Thermus thermophilus HB27 ». Journal of Biological Chemistry 286, n^o 12 (1 février 2011) : 9977–84. http://dx.doi.org/10.1074/jbc.m110.212688.

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Secretins are a family of large bacterial outer membrane protein complexes mediating the transport of complex structures, such as type IV pili, DNA and filamentous phage, or various proteins, such as extracellular enzymes and pathogenicity determinants. PilQ of the thermophilic bacterium Thermus thermophilus HB27 is a member of the secretin family required for natural transformation. Here we report the isolation, structural, and functional analyses of a unique PilQ from T. thermophilus. Native PAGE, gel filtration chromatography, and electrophoretic mobility shift analyses indicated that PilQ forms a macromolecular homopolymeric complex that binds dsDNA. Electron microscopy showed that the PilQ complex is 15 nm wide and 34 nm long and consists of an extraordinary stable “cone” and “cup” structure and five ring structures with a large central channel. Moreover, the electron microscopic images together with secondary structure analyses combined with structural data of type II protein secretion system and type III protein secretion system secretins suggest that the individual rings are formed by conserved domains of alternating α-helices and β-sheets. The unprecedented length of the PilQ complex correlated well with the distance between the inner and outer membrane of T. thermophilus. Indeed, PilQ was found immunologically in both membranes, indicating that the PilQ complex spans the entire cell periphery of T. thermophilus. This is consistent with the hypothesis that PilQ accommodates a PilA4 comprising pseudopilus mediating DNA transport across the outer membrane and periplasmic space in a single-step process.

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Li, James P., Ta-Min Chang, David Wagner et William Y. Chey. « Pancreatic phospholipase A2 from the small intestine is a secretin-releasing factor in rats ». American Journal of Physiology-Gastrointestinal and Liver Physiology 281, n^o 2 (1 août 2001) : G526—G532. http://dx.doi.org/10.1152/ajpgi.2001.281.2.g526.

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A secretin-releasing activity exists in the upper small intestine and pancreatic juice in the rat and the dog. Group I pancreatic phospholipase A2(PLA2) in canine pancreatic juice and porcine pancreatic PLA2 stimulate the release of secretin from both STC-1 cells and a secretin-producing cell (S cell)-enriched preparation isolated from rat duodenal mucosa. We investigated the distribution and release of pancreatic PLA2-like immunoreactivity in the gastrointestinal tract and the role of PLA2 on the release of secretin and pancreatic exocrine secretion in response to duodenal acidification in anesthetized rats. PLA2-like immunoreactivity was detected in the mucosa throughout the gastrointestinal tract. High concentrations of PLA2 were found in both the small intestine and the pancreas. Duodenal acidification significantly increased the release of PLA2from the upper small intestine (385% over basal secretion). Intravenous infusion of an anti-PLA2 serum (anti-PLA2) dose-dependently inhibited the release of secretin and pancreatic exocrine secretion in response to duodenal acid perfusion. Preincubation of the concentrate of intestinal acid perfusate (10-fold) from donor rats with the anti-PLA2significantly suppressed its stimulation of secretin release and pancreatic exocrine secretion in recipient rats. We conclude that pancreatic PLA2 also functions as a secretin-releasing factor in the small intestine that mediates acid-stimulated release of secretin in rats.

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Dehaye, J. P., J. Winand, C. Damien, F. Gomez, P. Poloczek, P. Robberecht, A. Vandermeers, M. C. Vandermeers-Piret, M. Stievenart et J. Christophe. « Receptors involved in helodermin action on rat pancreatic acini ». American Journal of Physiology-Gastrointestinal and Liver Physiology 251, n^o 5 (1 novembre 1986) : G602—G610. http://dx.doi.org/10.1152/ajpgi.1986.251.5.g602.

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Helodermin is a new peptide isolated from the venom of Heloderma suspectum. Its effects on rat pancreatic acini were compared with those of secretin and vasoactive intestinal peptide (VIP). Four classes of receptors with decreasing affinity for secretin (S1, S2, S3, and S4) were first delineated. Occupancy of S1 and S2 by secretin was responsible for a biphasic adenosine 3',5'-cyclic monophosphate (cAMP) response. S3 was VIP preferring so that the VIP-induced increase in cAMP could be inhibited by VIP-(10 --28). S2 and S3 allowed cAMP elevation, protein phosphorylation, weak secretory effects, and potentiation of cholecystokinin octapeptide (CCK-8) when occupied by secretin and VIP, respectively. A more efficient exocytosis was observed with secretin interacting with low-affinity receptors S4. Helodermin increased cAMP levels 14-fold, this increase being inhibited by VIP-(10–28). Low concentrations of helodermin stimulated amylase secretion twofold and potentiated secretion by CCK-8. High concentrations of helodermin stimulated secretion another 2.6-fold. Helodermin bound to the four secretin receptors with a weak selectivity. At low concentration, helodermin stimulated cAMP elevation, protein phosphorylation, amylase release, and potentiation of CCK-8 through S3, whereas at high concentration it stimulated secretion via S4.

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Li, James P., Kae Yol Lee, Ta-Min Chang et William Y. Chey. « MEK inhibits secretin release and pancreatic secretion : roles of secretin-releasing peptide and somatostatin ». American Journal of Physiology-Gastrointestinal and Liver Physiology 280, n^o 5 (1 mai 2001) : G890—G896. http://dx.doi.org/10.1152/ajpgi.2001.280.5.g890.

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We investigated the mechanism of action of methionine enkephalin (MEK) on HCl-stimulated secretin release and pancreatic exocrine secretion. Anesthetized rats with pancreatobiliary cannulas and isolated upper small intestinal loops were perfused intraduodenally with 0.01 N HCl while bile and pancreatic juice were diverted. The effect of intravenous MEK on acid-stimulated secretin release and pancreatic exocrine secretion was then studied with or without coinfusion of naloxone, an anti-somatostatin (SS) serum, or normal rabbit serum. Duodenal acid perfusate, which contains secretin-releasing peptide (SRP) activity, was collected from donor rats with or without pretreatment with MEK, MEK + naloxone, or MEK + anti-SS serum, concentrated by ultrafiltration, and neutralized. The concentrated acid perfusate (CAP), which contains SRP bioactivity, was infused intraduodenally into recipient rats. MEK increased plasma SS concentration and inhibited secretin release and pancreatic fluid and bicarbonate secretion dose-dependently. The inhibition was partially reversed by naloxone and anti-SS serum but not by normal rabbit serum. In recipient rats, CAP increased plasma secretin level and pancreatic secretion. CAP SRP bioactivity decreased when it was collected from MEK-treated donor rats; this was partially reversed by coinfusion with naloxone or anti-SS serum. These results suggest that in the rat, MEK inhibition of acid-stimulated pancreatic secretion and secretin release involves suppression of SRP activity release. Thus the MEK inhibitory effect appears to be mediated in part by endogenous SS.

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Jo, Y. H., Y. L. Lee, K. Y. Lee, T. M. Chang et W. Y. Chey. « Neurohormonal mechanism of pancreatic exocrine secretion stimulated by sodium oleate and L-tryptophan in dogs ». American Journal of Physiology-Gastrointestinal and Liver Physiology 263, n^o 1 (1 juillet 1992) : G12—G16. http://dx.doi.org/10.1152/ajpgi.1992.263.1.g12.

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In the present investigation, we have studied the effect of atropine on the pancreatic secretion stimulated by intraduodenal administration of either sodium oleate or exogenous cholecystokinin (CCK). In four dogs prepared with gastric and Thomas duodenal cannulas, pancreatic juice was collected for measurement of volume, bicarbonate, and protein output, and peripheral venous blood samples were obtained for radioimmunoassay of both secretin and CCK. Volume, bicarbonate, and protein output of the pancreatic juice increased significantly in response to sodium oleate (1-4 mmol/h) in a dose-dependent manner. The increase in pancreatic secretion paralleled the increments in both plasma CCK and secretin. Atropine given intravenously suppressed completely both pancreatic secretion and release of CCK stimulated by sodium oleate, whereas the release of secretin was not affected. Pancreatic secretion was significantly increased in a dose-dependent manner by exogenous CCK octapeptide (CCK-8) at 16, 32, and 64 micrograms (14, 28, and 56 pmol).kg-1.h-1. Atropine inhibited protein output only partially, but it did not influence bicarbonate output. In five additional dogs, the effect of atropine on L-tryptophan-stimulated pancreatic secretion was studied. Interestingly, atropine failed to influence the CCK release and pancreatic secretion of volume and bicarbonate, except for protein secretion, which was significantly inhibited. It was shown previously that atropine inhibited significantly the pancreatic secretion of bicarbonate stimulated by secretin in physiological doses. Thus we conclude that the inhibition by atropine of the pancreatic exocrine secretion stimulated by sodium oleate is mediated by both suppression of CCK release and inhibition of action of secretin on the exocrine pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)

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Hegyi, Péter, Zoltán Rakonczay, László Tiszlavicz, András Varró, András Tóth, Gábor Rácz, Gábor Varga, Michael A. Gray et Barry E. Argent. « Protein kinase C mediates the inhibitory effect of substance P on HCO3− secretion from guinea pig pancreatic ducts ». American Journal of Physiology-Cell Physiology 288, n^o 5 (mai 2005) : C1030—C1041. http://dx.doi.org/10.1152/ajpcell.00430.2003.

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The inhibitory control of pancreatic ductal HCO3− secretion may be physiologically important in terms of limiting the hydrostatic pressure developed within the ducts and in terms of switching off pancreatic secretion after a meal. Substance P (SP) inhibits secretin-stimulated HCO3− secretion by modulating a Cl−-dependent HCO3− efflux step at the apical membrane of the duct cell (Hegyi P, Gray MA, and Argent BE. Am J Physiol Cell Physiol 285: C268–C276, 2003). In the present study, we have shown that SP is present in periductal nerves within the guinea pig pancreas, that PKC mediates the effect of SP, and that SP inhibits an anion exchanger on the luminal membrane of the duct cell. Secretin (10 nM) stimulated HCO3− secretion by sealed, nonperfused, ducts about threefold, and this effect was totally inhibited by SP (20 nM). Phorbol 12,13-dibutyrate (PDBu; 100 nM), an activator of PKC, reduced basal HCO3− secretion by ∼40% and totally blocked secretin-stimulated secretion. In addition, bisindolylmaleimide I (1 nM to 1 μM), an inhibitor of PKC, relieved the inhibitory effect of SP on secretin-stimulated HCO3− secretion and also reversed the inhibitory effect of PDBu. Western blot analysis revealed that guinea pig pancreatic ducts express the α-, βI-, δ-, ε-, η-, θ-, ζ-, and μ-isoforms of PKC. In microperfused ducts, luminal H2DIDS (0.5 mM) caused intracellular pH to alkalinize and, like SP, inhibited basal and secretin-stimulated HCO3− secretion. SP did not inhibit secretion further when H2DIDS was present in the lumen, suggesting that SP and H2DIDS both inhibit the activity of an anion exchanger on the luminal membrane of the duct cell.

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Alimoukhamedova, G. A., et Z. Yu Khalimova. « ANDROGEN-SECRETING ADRENAL TUMORS ». International Journal of Medical Sciences And Clinical Research 02, n^o 04 (1 avril 2022) : 16–22. http://dx.doi.org/10.37547/ijmscr/volume02issue04-03.

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The objective of this research was to study clinical peculiarities of androgen-secreting tumors in adrenals dependent on age and gender. Among the patients with various neoplasms in adrenals (n=282), who received out-patient and in-patient treatment in the Republican Specialized Scientific Practical Medical Center of Endocrinology of the Uzbekistan Public Healthcare Ministry within the period from 2000 to 2018, androgen-secreting tumors were diagnosed in 9(3.2%) patients: 3(33.3%) men and 6(66.7%) women aged from 1.7 to 34 years old. As well as in the other groups with adrenal neoplasms, there was double prevailing of women. However, correlation of separate age subgroups was significantly different. In this group of patients specific weight of children increased (55.6%) compared to adults under 44 years old (44.4%). In spite of similar etiopathogenetic basis analysis of clinical manifestations of adrenal androgen-secreting tumors in children and adults revealed some differences. So, performed analysis confirms the presence of several symptoms in children, symptoms which are not observed in adults. On the other hand, somatic disorders in adults are more expressed than in children.

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Lake-Bakaar, G., et Joan Preece. « Luminal secretin : Artefact, direct secretion or basal secretion with paracellular transport ? » Gastroenterology 92, n^o 6 (juin 1987) : 2062. http://dx.doi.org/10.1016/0016-5085(87)90692-5.

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