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Journal articles on the topic 'Secretion'
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1
Park, Hyung Seo, Hyeok Yil Kwon, Yun Lyul Lee, William Y. Chey, and 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, no. 4 (April 1, 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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Possot, Odile M., Guillaume Vignon, Natalia Bomchil, Frank Ebel, and Anthony P. Pugsley. "Multiple Interactions between Pullulanase Secreton Components Involved in Stabilization and Cytoplasmic Membrane Association of PulE." Journal of Bacteriology 182, no. 8 (April 15, 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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Blocker, Ariel, Pierre Gounon, Eric Larquet, Kirsten Niebuhr, Véronique Cabiaux, Claude Parsot, and Philippe Sansonetti. "The Tripartite Type III Secreton of Shigella flexneri Inserts Ipab and Ipac into Host Membranes." Journal of Cell Biology 147, no. 3 (November 1, 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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Pugsley, Anthony P., Nicolas Bayan, and 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, no. 4 (February 15, 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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Villanger, O., T. Veel, and 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, no. 4 (October 1, 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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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, no. 7 (April 4, 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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Frank, Steven A. "Microbial secretor–cheater dynamics." Philosophical Transactions of the Royal Society B: Biological Sciences 365, no. 1552 (August 27, 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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Park, Hyung Seo, and 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, no. 4 (October 1, 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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Solomon, Travis E., John H. Walsh, Louis Bussjaeger, Yumei Zong, James W. Hamilton, F. J. Ho, Terry D. Lee, and Joseph R. Reeve. "COOH-terminally extended secretins are potent stimulants of pancreatic secretion." American Journal of Physiology-Gastrointestinal and Liver Physiology 276, no. 4 (April 1, 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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Deng, Xiaoying, Dulce R. Guarita, Martha R. A. Pedroso, Christianna Kreiss, Paul G. Wood, Alan F. Sved, and 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, no. 2 (August 1, 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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Olsen, Ole, Morten Wøjdemann, Belinda Berner, Gunvor Christiansen, and Berit Sternby. "Secretin and Gastric Lipase Secretion." Digestion 59, no. 6 (1998): 655–59. http://dx.doi.org/10.1159/000007571.
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Greco, A., R. Manna, G. Ghirlanda, L. Altomonte, and A. Bertoli. "Does Secretin Control Insulin Secretion?" Experimental and Clinical Endocrinology & Diabetes 84, no. 04 (July 17, 2009): 81–86. http://dx.doi.org/10.1055/s-0029-1210369.
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Beglinger, C., E. Kohler, I. Whitehouse, and K. Gyr. "Secretin and pancreatic enzyme secretion." Gut 26, no. 3 (March 1, 1985): 320–22. http://dx.doi.org/10.1136/gut.26.3.320.
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Noguchi, K., J. Arita, A. Nagamoto, M. Hosaka, and F. Kimura. "A quantitative analysis of testosterone action on FSH secretion from individual pituitary cells using the cell immunoblot assay." Journal of Endocrinology 148, no. 3 (March 1996): 427–33. http://dx.doi.org/10.1677/joe.0.1480427.
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Abstract We investigated the effects of testosterone on FSH secretion from male rat anterior pituitary cells in culture at the single cell level. Anterior pituitary cells cultured with or without 10 ng/ml testosterone for 72 h were mono-dispersed and subjected to cell immunoblot assays for FSH. Cell blots specific for FSH were quantified by means of a microscopic image analyzer. The number of FSH-secreting cells detected as immunoreactive cell blots on the transfer membrane represented 4·1% of total pituitary cells applied on the membrane. The amount of FSH secreted by single cells varied from <20 to >8 000 fg/cell/h. The number of FSH-secreting cells was not changed by the addition of 10 ng/ml testosterone into the culture medium. Testosterone administration increased the mean FSH secretion by 64% after 3 h incubation, resulting in a shift to the right in the frequency distribution of FSH secretion from single cells. The total amount of FSH, namely the sum of FSH secreted by each FSH-secreting cell, was increased by 92% by the addition of testosterone. However, mean amounts of FSH secretion by the top ten cells of the largest secretor subgroup (>5 pg/cell/3 h) were not different between control and testosterone-treated groups. The present study analyzed, for the first time, FSH secretion from rat anterior pituitary cells at the single cell level. The results suggest that stimulation by testosterone of FSH secretion in vitro is not due to an increase in the number of FSH-secreting cells but to an increase in FSH secretion from each cell. Journal of Endocrinology (1996) 148, 427–433
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Blot-Chabaud, M., M. Dumont, M. Corbic, and 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, no. 6 (June 1, 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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Lake-Bakaar, G., and Joan Preece. "Luminal secretin: Artefact, direct secretion or basal secretion with paracellular transport ?" Gastroenterology 92, no. 6 (June 1987): 2062. http://dx.doi.org/10.1016/0016-5085(87)90692-5.
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Kim, C. D., P. Li, K. Y. Lee, D. H. Coy, and 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, no. 5 (November 1, 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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Li, James P., Ta-Min Chang, and 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, no. 4 (April 1, 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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Solomon, Travis E., Gabor Varga, Ning Zeng, S. Vincent Wu, John H. Walsh, and Joseph R. Reeve. "Different actions of secretin and Gly-extended secretin predict secretin receptor subtypes." American Journal of Physiology-Gastrointestinal and Liver Physiology 280, no. 1 (January 1, 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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Song, Y., P. Li, K. Y. Lee, T. M. Chang, and 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, no. 3 (September 1, 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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Kanno, Noriatsu, Gene LeSage, Shannon Glaser, and Gianfranco Alpini. "Regulation of cholangiocyte bicarbonate secretion." American Journal of Physiology-Gastrointestinal and Liver Physiology 281, no. 3 (September 1, 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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Lazzaro, Mark D., and William W. Thomson. "Ultrastructural localization of calcium in the organic acid secreting trichomes of chickpea (Cicer arietinum)." Canadian Journal of Botany 70, no. 12 (December 1, 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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Ko, S. B. H., S. Naruse, M. Kitagawa, H. Ishiguro, M. Murakami, and T. Hayakawa. "Arginine vasopressin inhibits fluid secretion in guinea pig pancreatic duct cells." American Journal of Physiology-Gastrointestinal and Liver Physiology 277, no. 1 (July 1, 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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Caligiuri, Alessandra, Shannon Glaser, Rebecca E. Rodgers, Jo Lynne Phinizy, Willie Robertson, Emanuela Papa, Massimo Pinzani, and 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, no. 4 (October 1, 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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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, no. 4 (October 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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Alpini, G., S. Glaser, W. Robertson, R. E. Rodgers, J. L. Phinizy, J. Lasater, and G. D. LeSage. "Large but not small intrahepatic bile ducts are involved in secretin-regulated ductal bile secretion." American Journal of Physiology-Gastrointestinal and Liver Physiology 272, no. 5 (May 1, 1997): G1064—G1074. http://dx.doi.org/10.1152/ajpgi.1997.272.5.g1064.
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We have shown that agonist-regulated ductal secretion is limited to large cholangiocytes. To directly study cholangiocyte heterogeneity along the length of the normal biliary tree, we defined the genetic and functional expression of agonist-induced ductal secretion in intrahepatic bile duct units (IBDU) of different sizes. Small IBDU (< 15-microns diam) were separated from large IBDU (> or = 15-microns diam), and then ducts of different sizes were characterized by morphometric analysis, gene expression, secretin-induced adenosine 3',5'-cyclic monophosphate (cAMP) synthesis, and secretion by change in luminal size in response to agonists. IBDU diameters ranged from 11 to 65 microns. Secretin increased ductal secretion solely in large IBDU. Forskolin induced a modest increase in ductal secretion in small IBDU but markedly increased ductal secretion in large IBDU. Secretion increased Cl-/HCO3- exchanger activity and cAMP levels in large but not small IBDU. Secretin receptor and Cl-/HCO3 exchanger mRNAs were detected only in large IBDU. We propose that agonist-induced ductal secretion occurs in large (> or = 15-microns diam) but not small (< 15-microns diam) intrahepatic ducts.
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Fiorucci, Stefano, Eleonora Distrutti, Barbara Federici, Barbara Palazzetti, Monia Baldoni, Antonio Morelli, and Giuseppe Cirino. "PAR-2 modulates pepsinogen secretion from gastric-isolated chief cells." American Journal of Physiology-Gastrointestinal and Liver Physiology 285, no. 3 (September 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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Alvaro, D., A. Mennone, and 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, no. 2 (August 1, 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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Vignon, Guillaume, Rolf Köhler, Eric Larquet, Stéphanie Giroux, Marie-Christine Prévost, Pascal Roux, and 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, no. 11 (June 1, 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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Jo, Y. H., Y. L. Lee, K. Y. Lee, T. M. Chang, and 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, no. 1 (July 1, 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, and 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, no. 5 (May 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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Seo, Jin, Anja Brencic, and 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, no. 3 (November 21, 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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Nylander, O., G. Flemstrom, D. Delbro, and L. Fandriks. "Vagal influence on gastroduodenal HCO3- secretion in the cat in vivo." American Journal of Physiology-Gastrointestinal and Liver Physiology 252, no. 4 (April 1, 1987): G522—G528. http://dx.doi.org/10.1152/ajpgi.1987.252.4.g522.
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Gastric and duodenal secretions of HCO3- were studied simultaneously in chloralose-anesthetized cats. The adrenals were ligated, and the cervical vagal as well as the abdominal splanchnic nerves were cut. Gastric secretions of H+ and HCO3- were calculated from measurements of the pH and PCO2 in the luminal perfusate. A duodenal segment devoid of Brunner's glands and pancreaticobilary secretions was cannulated in situ and the alkaline secretion determined by continuous titration at luminal pH 7.4. Electrical stimulation in the distal direction for 10–15 min of the cervical vagal nerves resulted in a 6- to 10-fold increase in gastric H+ and in a 20–60% rise in gastric HCO-3 secretion. Duodenal HCO3- secretion increased by 65–155%. Gastric basal secretions of H+ and HCO3- were not affected by atropine or hexamethonium, but both agents inhibited basal duodenal HCO3- secretion. Hexamethonium abolished and atropine reduced the rise in all secretions in response to vagal nerve stimulation. Thus gastroduodenal mucosal HCO3- secretion is stimulated by vagal mechanisms involving action on nicotinic as well as on muscarinic receptors and possibly also noncholinergic neurotransmission.
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Sutliff, V. E., J. P. Raufman, R. T. Jensen, and 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, no. 1 (July 1, 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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Hamada, Hiroyuki, Hiroshi Ishiguro, Akiko Yamamoto, Sachiko Shimano-Futakuchi, Shigeru B. H. Ko, Toshiyuki Yoshikawa, Hidemi Goto, et al. "Dual effects of n-alcohols on fluid secretion from guinea pig pancreatic ducts." American Journal of Physiology-Cell Physiology 288, no. 6 (June 2005): C1431—C1439. http://dx.doi.org/10.1152/ajpcell.00373.2004.
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Ethanol strongly augments secretin-stimulated, but not acetylcholine (ACh)-stimulated, fluid secretion from pancreatic duct cells. To understand its mechanism of action, we examined the effect of short-chain n-alcohols on fluid secretion and intracellular Ca2+ concentration ([Ca2+]i) in guinea pig pancreatic ducts. Fluid secretion was measured by monitoring the luminal volume of isolated interlobular ducts. [Ca2+]i was estimated using fura-2 microfluorometry. Methanol and ethanol at 0.3–10 mM concentrations significantly augmented fluid secretion and induced a transient elevation of [Ca2+]i in secretin- or dibutyryl adenosine 3′,5′-cyclic monophosphate (DBcAMP)-stimulated ducts. However, they failed to affect fluid secretion and [Ca2+]i in unstimulated and ACh-stimulated ducts. In contrast, propanol and butanol at 0.3–10 mM concentrations significantly reduced fluid secretion and decreased [Ca2+]i in unstimulated ducts and in ducts stimulated with secretin, DBcAMP, or ACh. Both stimulatory and inhibitory effects of n-alcohols completely disappeared after their removal from the perfusate. Propanol and butanol inhibited the plateau phase, but not the initial peak, of [Ca2+]i response to ACh as well as the [Ca2+]i elevation induced by thapsigargin, suggesting that they inhibit Ca2+ influx. Removal of extracellular Ca2+ reduced [Ca2+]i in duct cells and completely abolished secretin-stimulated fluid secretion. In conclusion, there is a distinct cutoff point between ethanol (C2) and propanol (C3) in their effects on fluid secretion and [Ca2+]i in duct cells. Short-chain n-alcohols appear to affect pancreatic ductal fluid secretion by activating or inhibiting the plasma membrane Ca2+ channel.
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Coskun, Tamer, Heidi K. Baumgartner, Shaoyou Chu, and Marshall H. Montrose. "Coordinated regulation of gastric chloride secretion with both acid and alkali secretion." American Journal of Physiology-Gastrointestinal and Liver Physiology 283, no. 5 (November 1, 2002): G1147—G1155. http://dx.doi.org/10.1152/ajpgi.00184.2002.
Full textAbstract:
Gastric secretion of hydrochloric acid requires protons and chloride, yet the mechanisms and regulation of gastric chloride secretion remain unclear. We developed an in vivo technique to simultaneously measure acid/base and chloride secretion into the gastric lumen of anesthetized rats. The cannulated stomach lumen was perfused with weakly pH-buffered chloride-free solution containing a chloride-sensitive fluorophore [5 μM N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE)]. Gastric acid and chloride secretion was detected in gastric effluents by 1) flow-through pH electrode and 2) MQAE fluorescence. Gastric effluent was also collected at 1-min intervals for independent determination of chloride amount by chloridometer. In all conditions, both optical and chemical determinations of chloride report similar amounts of secreted chloride. During luminal perfusion with pH 5 solution, net acid and chloride secretion into the lumen was observed. Pentagastrin stimulated both secretions. In contrast, proton pump inhibition (omeprazole) caused alkalinization of the gastric effluent, but chloride secretion was not diminished. During luminal pH 3 perfusion, net alkali secretion was observed, and chloride secretion at luminal pH 3 was greater than pH 5. When tissue is pretreated with omeprazole at luminal pH 3, the addition of prostaglandin E2 synchronously stimulates both alkali and chloride secretion. Results suggest that both acid and alkali secretions are separately coupled with chloride secretion.
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Kitsukawa, Y., C. Felley, D. C. Metz, and R. T. Jensen. "Thapsigargin defines roles of Ca2+ in initial, sustained, and potentiated stimulation of pepsinogen secretion." American Journal of Physiology-Gastrointestinal and Liver Physiology 266, no. 4 (April 1, 1994): G613—G623. http://dx.doi.org/10.1152/ajpgi.1994.266.4.g613.
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The roles of Ca2+ in agonist-induced pepsinogen secretion from guinea pig chief cells remain unclear. We used cholecystokinin octapeptide (CCK-8) or secretin alone or with thapsigargin (TG) to clarify these roles. TG releases Ca2+ from intracellular stores by inhibiting microsomal Ca(2+)-adenosinetriphosphatase (ATPase), thereby depleting intracellular Ca2+ (Cai2+) stores. In most cells TG also causes Ca2+ influx. In the present study, with an extracellular Ca2+ concentration ([Ca2+]o) of 1.5 mM, CCK-8 (0.1 microM) caused a rapid increase in pepsinogen secretion; however, the rate decreased with time. With [Ca2+]o = 0, the initial increase was similar but later secretion was abolished, suggesting that Ca2+ influx was important for sustained secretion. With [Ca2+]o = 1.5 mM, TG (0.1 microM) caused a 2.7-fold sustained increase in in Cai2+ concentration ([Ca2+]i) and a ninefold sustained increase in pepsinogen secretion. With [Ca2+]o = 0, TG caused a transient 66% increase in [Ca2+]i and a 50% increase in pepsinogen secretion. The time course of TG-induced pepsinogen secretion correlated with the time course of TG-induced increases in [Ca2+]i. These data demonstrated that Ca2+ influx itself was a potent stimulant of pepsinogen secretion. We further focused on the roles of increasing [Ca2+]i from Cai2+ stores. With or without extracellular Ca2+ (Cao2+) present, addition of CCK-8 (0.1 microM) 10 min after TG caused no further increase in [Ca2+]i, demonstrating depletion of the inositol 1,4,5-trisphosphate-sensitive pool. The Ca(2+)-mobilizing agent CCK-8 caused no pepsinogen secretion 10 min after TG preincubation, demonstrating that mobilization of Ca2+ from intracellular stores was important in the rapid initial phase stimulation of pepsinogen secretion caused by CCK-8. In contrast, preincubation with TG had no effect on pepsinogen secretion by secretin, an agent that increases adenosine 3',5'-cyclic monophosphate. A 6-min preincubation with TG potentiated the subsequent stimulation of pepsinogen secretion caused by secretin in the presence of Cao2+ where [Ca2+]i remained elevated. However, TG-induced potentiations of secretin-stimulated pepsinogen secretion was abolished once [Ca2+]i had returned to the basal level in the absence of Cao2+.(ABSTRACT TRUNCATED AT 400 WORDS)
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Glaser, Shannon, Domenico Alvaro, Tania Roskams, Jo Lynne Phinizy, George Stoica, Heather Francis, Yoshiyuki Ueno, et al. "Dopaminergic inhibition of secretin-stimulated choleresis by increased PKC-γ expression and decrease of PKA activity." American Journal of Physiology-Gastrointestinal and Liver Physiology 284, no. 4 (April 1, 2003): G683—G694. http://dx.doi.org/10.1152/ajpgi.00302.2002.
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To determine the role and mechanisms of action by which dopaminergic innervation modulates ductal secretion in bile duct-ligated rats, we determined the expression of D1, D2, and D3 dopaminergic receptors in cholangiocytes. We evaluated whether D1, D2 (quinelorane), or D3 dopaminergic receptor agonists influence basal and secretin-stimulated choleresis and lumen expansion in intrahepatic bile duct units (IBDU) and cAMP levels in cholangiocytes in the absence or presence of BAPTA-AM, chelerythrine, 1-(5-isoquinolinylsulfonyl)-2-methyl piperazine (H7), or rottlerin. We evaluated whether 1) quinelorane effects on ductal secretion were associated with increased expression of Ca2+-dependent PKC isoforms and 2) increased expression of PKC causes inhibition of PKA activity. Quinelorane inhibited secretin-stimulated choleresis in vivo and IBDU lumen space, cAMP levels, and PKA activity in cholangiocytes. The inhibitory effects of quinelorane on secretin-stimulated ductal secretion and PKA activity were blocked by BAPTA-AM, chelerythrine, and H7. Quinelorane effects on ductal secretion were associated with activation of the Ca2+-dependent PKC-γ but not other PKC isoforms. The dopaminergic nervous system counterregulates secretin-stimulated ductal secretion in experimental cholestasis.
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Li, P., T. M. Chang, and W. Y. Chey. "Secretin inhibits gastric acid secretion via a vagal afferent pathway in rats." American Journal of Physiology-Gastrointestinal and Liver Physiology 275, no. 1 (July 1, 1998): G22—G28. http://dx.doi.org/10.1152/ajpgi.1998.275.1.g22.
Full textAbstract:
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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Lee, K. Y., L. Zhou, X. S. Ren, T. M. Chang, and W. Y. Chey. "An important role of endogenous insulin on exocrine pancreatic secretion in rats." American Journal of Physiology-Gastrointestinal and Liver Physiology 258, no. 2 (February 1, 1990): G268—G274. http://dx.doi.org/10.1152/ajpgi.1990.258.2.g268.
Full textAbstract:
We have investigated a physiological role of endogenous insulin on exocrine pancreatic secretion stimulated by a liquid meal as well as exogenous secretin and cholecystokinin octapeptide (CCK-8) in conscious rats. Each rat was prepared with a chronic pancreatic fistula and an indwelling catheter in a jugular vein. Oral ingestion of a liquid meal (5 ml) resulted in significant increases in pancreatic secretion, including volume, bicarbonate, and amylase output, in these rats. A rabbit anti-insulin serum (1.0 ml) given intravenously completely blocked the postprandial exocrine pancreatic secretion, whereas a normal rabbit serum did not influence the pancreatic secretion in the same rats. When pancreatic secretion was stimulated by intravenous administration of both secretin and CCK-8 in three different doses, including 0.015, 0.03, and 0.06 clinical unit and microgram.kg-1.h-1, respectively, volume, bicarbonate, and amylase output increased significantly in a dose-dependent manner. This increase in pancreatic secretion was also completely blocked by a rabbit anti-insulin serum, whereas it was not influenced by a normal rabbit serum. The amount of the antiserum employed abolished the postprandial increases in plasma insulin concentration. We conclude that endogenous insulin plays an important role on the regulation of postprandial pancreatic secretion in rats. Furthermore, for the stimulatory action of the two intestinal hormones secretin and CCK-8 on the pancreatic exocrine secretion, endogenous insulin is need.
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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, and 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, no. 5 (November 1, 1997): G1061—G1070. http://dx.doi.org/10.1152/ajpgi.1997.273.5.g1061.
Full textAbstract:
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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Medvedev, M. A., and I. V. Roudin. "The role of opioid peptides in the regulation of secretin-stimulated bile secretion." Bulletin of Siberian Medicine 5, no. 3 (September 30, 2006): 37–41. http://dx.doi.org/10.20538/1682-0363-2006-3-37-41.
Full textAbstract:
Influence of intraperitoneal dalargin (dand m-opioid agonist), DADLE (d-opioid agonist), DAGO (m-opioid agonist) and U50488 (k-opioid agonist) on bile secretion which is stimulated by secretin was studied in sharp experiments on white rats. All opioids studied is demonstrated to suppress secretory response of liver upon secretin in different extent. We suppose that opioidergic regulation system has different effect on bile secretion in dependence of baseline level of physiologic secretion.
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O’Neal, Pamela V., Cindy L. Munro, Mary Jo Grap, and Sarah M. Rausch. "Subglottic Secretion Viscosity and Evacuation Efficiency." Biological Research For Nursing 8, no. 3 (January 2007): 202–9. http://dx.doi.org/10.1177/1099800406295517.
Full textAbstract:
Ventilator-associated pneumonia (VAP) is a common nosocomial pneumonia that occurs in critically ill patients and results in mortality rates as high as 71%. Subglottic secretions (SSs) are a known risk factor. Several clinical trials have shown that continuous aspiration of subglottic secretions (CASS) reduces the risk of VAP by nearly half. Optimal suction pressure levels needed to efficiently evacuate viscous SSs are unknown. The purpose of this study was to describe SSs and the effective suction pressure (20 mmHg, 30 mmHg, 40 mmHg, and 50 mmHg) needed to maximize evacuation efficiency based on SS volume (2 ml, 4 ml, and 6 ml) and viscosity (watery, thick, and gel-like). A laboratory model was designed to replicate a human trachea. Thick secretions had the highest percentage of mean recovery representative of evacuation efficiency of SSs (mean recovery of 86%). The suction pressure of 30 mmHg had the highest overall mean of secretion recovery (83%) across all viscosity types and amounts. This study demonstrated that higher viscosity secretions were easier to evacuate than lower viscosity secretions when 30-mmHg suction pressure was applied. Management of secretion viscosity may assist in secretion removal and delay VAP development. With increased understanding of the molecular structure of SSs, there is the potential that clinicians will be able to manipulate secretion viscoelastic properties to maximize evacuation efficiency of the secretions. Further research is needed to identify safe suction pressures for optimal evacuation of SSs in human subjects.
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Sætre, S. S., N. J. Andersen, T. Houe, P. Svendsen, J. F. Rehfeld, O. Olsen, and O. B. Schaffalitzky de Muckadell. "Regulation of porcine biliary secretion by secretin." Acta Physiologica Scandinavica 163, no. 1 (May 1998): 113–19. http://dx.doi.org/10.1046/j.1365-201x.1998.00349.x.
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Li, James P., Kae Yol Lee, Ta-Min Chang, and 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, no. 5 (May 1, 2001): G890—G896. http://dx.doi.org/10.1152/ajpgi.2001.280.5.g890.
Full textAbstract:
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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Park, Hyung Seo, Yun Lyul Lee, Hyeok Yil Kwon, William Y. Chey, and Hyoung Jin Park. "Significant cholinergic role in secretin-stimulated exocrine secretion in isolated rat pancreas." American Journal of Physiology-Gastrointestinal and Liver Physiology 274, no. 2 (February 1, 1998): G413—G418. http://dx.doi.org/10.1152/ajpgi.1998.274.2.g413.
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Effects of intrapancreatic cholinergic activation by electrical field stimulation (EFS) on secretin-stimulated pancreatic exocrine secretion were investigated in the totally isolated perfused rat pancreas. EFS at 15 V, 2 ms, and 8 Hz for 45 min markedly increased spontaneous pancreatic secretion. This increase was completely inhibited by tetrodotoxin (1 μM) but not by hexamethonium (100 μM). Atropine (2 μM) significantly reduced the EFS-evoked volume flow and amylase output by 52% and 80%, respectively. EFS further increased the secretin (12 pM)-stimulated pancreatic secretion of fluid and amylase. The increases of the two parameters were significantly suppressed by atropine by 28% and 72%, respectively. Interestingly, EFS significantly increased concentrations of somatostatin-like immunoreactivity in portal venous effluents. When pertussis toxin (200 ng/ml) or rabbit antisomatostatin serum (0.1 ml/10 ml; titer of 1:50,000) was intra-arterially administered, EFS further increased the secretin-stimulated pancreatic secretion. In conclusion, the activation of intrapancreatic cholinergic neurons potentiated the secretin action on pancreatic exocrine secretion in the rat. This potentiating effect was significantly reduced by local somatostatin released during EFS that activated intrapancreatic cholinergic tone.
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Siqueira, W. L., E. Salih, D. L. Wan, E. J. Helmerhorst, and F. G. Oppenheim. "Proteome of Human Minor Salivary Gland Secretion." Journal of Dental Research 87, no. 5 (May 2008): 445–50. http://dx.doi.org/10.1177/154405910808700508.
Full textAbstract:
Recent research efforts in oral biology have resulted in elucidation of the proteomes of major human salivary secretions and whole saliva. One might hypothesize that the proteome of minor gland secretions may show significantly different characteristics when compared with the proteomes of parotid or submandibular/sublingual secretions. To test this hypothesis, we conducted the first exploration into the proteome of minor salivary gland secretion. Minor gland secretion was obtained from healthy volunteers, and its components were subjected to liquid-chromatography-electrospray-ionization-tandem-mass-spectrometry. This led to the identification of 56 proteins, 12 of which had never been identified in any salivary secretion. The unique characteristics of the minor salivary gland secretion proteome are related to the types as well as the numbers of components present. The differences between salivary proteomes may be important with respect to specific oral functions.
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Berger, S., and J. P. Raufman. "Prostaglandin-induced pepsinogen secretion from dispersed gastric glands from guinea pig stomach." American Journal of Physiology-Gastrointestinal and Liver Physiology 249, no. 5 (November 1, 1985): G592—G598. http://dx.doi.org/10.1152/ajpgi.1985.249.5.g592.
Full textAbstract:
We examined the actions of several prostaglandins (PG) on pepsinogen secretion from dispersed gastric glands prepared from guinea pig stomach. Pepsinogen secretion was stimulated by PGA1, PGA2, PGB2, PGE1, and PGE2. PGE1 and PGE2 were 10 times more potent than PGA1 and PGA2. Reducing the incubation temperature from 37 degrees to 4 degrees C or adding carbonyl cyanide m-chlorophenylhydrazone reduced PG-stimulated pepsinogen secretion. PGE2-induced pepsinogen secretion was not altered by atropine or dibutyryl cGMP. Potentiation of pepsinogen secretion occurred with PGE2 plus carbachol or the calcium ionophore A23187 but not with PGE2 plus secretin or 8-bromo-cAMP. Isobutylmethylxanthine increased the potency and the efficacy of the action of PGE2 on pepsinogen secretion. These results indicate that PGE1, PGA2, PGB2, PGE1, and PGE2 can modulate pepsinogen secretion from dispersed gastric glands from guinea pig stomach. Moreover, potentiation of pepsinogen secretion occurs when PGE2 is combined with secretagogues whose actions appear to be mediated by changes in cellular calcium (carbachol and A23187) but not with secretagogues whose actions appear to be mediated by changes in cellular cAMP (secretin and 8-bromo-cAMP). These data suggest that PG-induced pepsinogen secretion may be mediated by changes in cellular cAMP.
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Li, P., T. M. Chang, D. Coy, and W. Y. Chey. "Inhibition of gastric acid secretion in rat stomach by PACAP is mediated by secretin, somatostatin, and PGE2." American Journal of Physiology-Gastrointestinal and Liver Physiology 278, no. 1 (January 1, 2000): G121—G127. http://dx.doi.org/10.1152/ajpgi.2000.278.1.g121.
Full textAbstract:
Pituitary adenylate cyclase-activating polypeptide (PACAP), existing in two variants, PACAP-27 and PACAP-38, is found in the enteric nervous system and regulates function of the digestive system. However, the regulatory mechanism of PACAP on gastric acid secretion has not been well elucidated. We investigated the inhibitory action of PACAP-27 on acid secretion and its mechanism in isolated vascularly perfused rat stomach. PACAP-27 in four graded doses (5, 10, 20, and 50 μg/h) was vascularly infused to determine its effect on basal and pentagastrin (50 ng/h)-stimulated acid secretion. To study the inhibitory mechanism of PACAP-27 on acid secretion, a rabbit antisecretin serum, antisomatostatin serum, or indomethacin was administered. Concentrations of secretin, somatostatin, PGE2, and histamine in portal venous effluent were measured by RIA. PACAP-27 dose-dependently inhibited both basal and pentagastrin-stimulated acid secretion. PACAP-27 at 10 μg/h significantly increased concentrations of secretin, somatostatin, and PGE2 in basal or pentagastrin-stimulated state. The inhibitory effect of PACAP-27 on pentagastrin-stimulated acid secretion was reversed 33% by an antisecretin serum, 80.0% by an antisomatostatin serum, and 46.1% by indomethacin. The antisecretin serum partially reduced PACAP-27-induced local release of somatostatin and PGE2. PACAP-27 at 10 μg/h elevated histamine level in portal venous effluent, which was further increased by antisomatostatin serum. However, antisomatostatin serum did not significantly increase acid secretion. It is concluded that PACAP-27 inhibits both basal and pentagastrin-stimulated gastric acid secretion. The effect of PACAP-27 is mediated by local release of secretin, somatostatin, and PGE2 in isolated perfused rat stomach. The increase in somatostatin and PGE2 levels in portal venous effluent is, in part, attributable to local action of the endogenous secretin.
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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, and J. Christophe. "Receptors involved in helodermin action on rat pancreatic acini." American Journal of Physiology-Gastrointestinal and Liver Physiology 251, no. 5 (November 1, 1986): G602—G610. http://dx.doi.org/10.1152/ajpgi.1986.251.5.g602.
Full textAbstract:
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.