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Zeitschriftenartikel zum Thema „Antiporno“

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Veröffentlicht am 25. Juni 2021

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1

Tonnessen, T. I., K. Sandvig und S. Olsnes. „Role of Na(+)-H+ and Cl(-)-HCO3- antiports in the regulation of cytosolic pH near neutrality“. American Journal of Physiology-Cell Physiology 258, Nr. 6 (01.06.1990): C1117—C1126. http://dx.doi.org/10.1152/ajpcell.1990.258.6.c1117.

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In Vero cells, Na(+)-H+ antiport as well as Na(+)-coupled and Na(+)-independent Cl(-)-HCO3- antiport are involved in regulation of cytosolic pH (pHi) after large (unphysiological) deviations from neutrality. In this paper we have studied to which extent each of the three antiports is involved in regulation of pHi after small deviations from neutrality expected to occur under physiological conditions. At physiological extracellular pH (pHo), inhibition of Na(+)-H+ exchange by amiloride did not alter pHi. At neutral and alkaline pHo, pHi was found to be lower in the presence of HCO3- than in its absence, whereas at acidic pHo, pHi was higher in the presence of HCO3- than in its nominal absence. Above pHi 6.5, the activity of the Na(+)-coupled Cl(-)-HCO3- antiport was higher than the Na(+)-H+ antiport. After a small reduction of pHi, the recovery of steady-state pHi was entirely dependent on Na(+)-coupled Cl(-)-HCO3- antiport, whereas after more pronounced acidification, also Na(+)-H+ exchange contributed to the acid extrusion. The Na(+)-independent Cl(-)-HCO3- antiport, which acts as an acidifying mechanism, was strongly activated at pHi greater than 7.1. The results indicate that at physiological pHo the steady-state pHi is largely determined by the activity of the two Cl(-)-HCO3- antiports, and they suggest that Na(+)-H+ exchange does not influence the resting pHi under these conditions.

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2

Cheng, J., K. Baldwin, A. A. Guffanti und T. A. Krulwich. „Na+/H+ antiport activity conferred by Bacillus subtilis tetA(L), a 5' truncation product of tetA(L), and related plasmid genes upon Escherichia coli.“ Antimicrobial Agents and Chemotherapy 40, Nr. 4 (April 1996): 852–57. http://dx.doi.org/10.1128/aac.40.4.852.

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An Escherichia coli transformant expressing the Bacillus subtilis tetA(L) gene from a weak promoter was challenged by growth on medium with low, increasing tetracycline concentrations. Changes in the substrate preference ratios of the TetA(L)-mediated resistances and antiports were examined in view of recent findings suggesting that TetA(L) catalyzes efflux of Na+ in exchange for protons in addition to having the ability to catalyze metal-tetracycline/H+ antiport. After growth of the transformant on 1 microgram or more of tetracycline per ml for 12 to 15 h, the tetA(L) gene in the plasmid was found to be disrupted by an IS10 element 50 bp from the 5' end of the coding sequence. This disrupted recombinant plasmid, pKB1, conferred greater tetracycline resistance and higher levels of membrane metal-tetracycline/proton antiport than the original plasmid, pJTA1, but conferred lower NA+ resistance and Na+/H+ antiport levels than the original plasmid. The results indicate that the 5' end of the gene is necessary for optimal Na+/H+ antiport but that some such activity as well as robust tetracycline/H+ antiport persists in its absence. Two plasmid genes, tet(K) and qacA, were compared with tetA(L) vis-à-vis their abilities to enhance the Na+/H+ antiporter activity of everted vesicles from E. coli transformants. tet(K), which is more closely related to tetA(L), catalyzed 22Na+ uptake by energized vesicles, whereas the less closely related qacA gene did not.

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3

Houle, Karen. „Antiporn Cons and Pros“. International Studies in Philosophy 30, Nr. 1 (1998): 79–90. http://dx.doi.org/10.5840/intstudphil1998301110.

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4

Eaton, A. W. „A Sensible Antiporn Feminism“. Ethics 117, Nr. 4 (Juli 2007): 674–715. http://dx.doi.org/10.1086/519226.

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5

CAVALIERE, MATTEO, und VINCENZO DEUFEMIA. „FURTHER RESULTS ON TIME-FREE P SYSTEMS“. International Journal of Foundations of Computer Science 17, Nr. 01 (Februar 2006): 69–89. http://dx.doi.org/10.1142/s012905410600370x.

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Membrane systems (currently called P systems) are parallel computing devices inspired by the structure and the functioning of living cells. A standard feature of P systems is that each rule is executed in exactly one time unit. Actually, in living cells different chemical reactions might take different times to be executed; moreover, it might be hard to know precisely such time of execution. For this reason, in [7] two models of P systems (time-free and clock-free P systems) have been defined and investigated, where the time of execution of the rules is arbitrary and the output produced by the system is always the same, independently of this time. Preliminary results concerning time-free and clock-free P system have been obtained in [6, 7, 8]. In this paper we continue these investigations by considering different combinations of possible ingredients. In particular, we present the universality of time-free P systems using bi-stable catalysts. Then, we prove that this result implies that is not possible to decide whether an arbitrary bi-stable catalytic P system is time-free. We present several results about time-free evolution-communication P systems, where the computation is a mixed application of evolution and symport/antiport rules. In this case we obtain the universality even by using non-cooperative evolution rules and antiports of weight one. Finally, we formulate several open problems.

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6

Ng, L. L., P. Delva und J. E. Davies. „Intracellular pH regulation of SV-40 virus transformed human MRC-5 fibroblasts and cell membrane cholesterol“. American Journal of Physiology-Cell Physiology 264, Nr. 4 (01.04.1993): C789—C793. http://dx.doi.org/10.1152/ajpcell.1993.264.4.c789.

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Alterations in membrane cholesterol could affect the activity of various membrane transporters, including the Na(+)-H+ antiport. The effect of cellular cholesterol depletion (with phosphatidylcholine liposomes) and enrichment (with cholesterol and phosphatidylcholine liposomes) on cellular pH regulation was studied in SV-40 virus transformed human MRC-5 fibroblasts. Cellular cholesterol depletion led to activation of the Na(+)-H+ antiport by an increased maximal velocity (Vmax) of the transporter, with no changes in the apparent dissociation constant (Kd) or Hill coefficient for intracellular H+. Cholesterol enrichment had no effect on the activation of the Na(+)-H+ antiport by intracellular acidosis. However, activation of the Na(+)-H+ antiport by an osmotic stimulus was enhanced in cholesterol-depleted cells and reduced in cholesterol-enriched cells. Liposomes that had no effect on cellular cholesterol did not alter the activation of Na(+)-H+ antiport activity by intracellular acidosis or an osmotic stimulus. Thus in situ modification of cellular cholesterol altered Na(+)-H+ antiport activity differently depending on the type of activating stimulus.

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7

Cutaia, M. V., N. Parks, J. Centracchio, S. Rounds, K. P. Yip und A. M. Sun. „Effect of hypoxic exposure on Na+/H+antiport activity, isoform expression, and localization in endothelial cells“. American Journal of Physiology-Lung Cellular and Molecular Physiology 275, Nr. 3 (01.09.1998): L442—L451. http://dx.doi.org/10.1152/ajplung.1998.275.3.l442.

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Little is known about the effects of prolonged hypoxic exposure on membrane ion transport activity. The Na+/H+antiport is an ion transport site that regulates intracellular pH in mammalian cells. We determined the effect of prolonged hypoxic exposure on human pulmonary arterial endothelial cell antiport activity, gene expression, and localization. Monolayers were incubated under hypoxic or normoxic conditions for 72 h. Antiport activity was determined as the rate of recovery from intracellular acidosis. Antiport isoform identification and gene expression were determined with RT-PCR and Northern and Western blots. Antiport localization and F-actin cytoskeleton organization were defined with immunofluorescent staining. Prolonged hypoxic exposure decreased antiport activity, with no change in cell viability compared with normoxic control cells. One antiport isoform [Na+/H+exchanger isoform (NHE) 1] that was localized to the basolateral cell surface was present in human pulmonary arterial endothelial cells. Hypoxic exposure had no effect on NHE1 mRNA transcript expression, but NHE1 protein expression was upregulated. Immunofluorescent staining demonstrated a significant alteration of the F-actin cytoskeleton after hypoxic exposure but no change in NHE1 localization. These results demonstrate that the decrease in NHE1 activity after prolonged hypoxic exposure is not related to altered gene expression. The change in NHE1 activity may have important consequences for vascular function.

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8

Southworth, Thomas W., Arthur A. Guffanti, Anne Moir und Terry A. Krulwich. „GerN, an Endospore Germination Protein ofBacillus cereus, Is an Na+/H+-K+ Antiporter“. Journal of Bacteriology 183, Nr. 20 (15.10.2001): 5896–903. http://dx.doi.org/10.1128/jb.183.20.5896-5903.2001.

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ABSTRACT GerN, a Bacillus cereus spore germination protein, exhibits homology to a widely distributed group of putative cation transporters or channel proteins. GerN complemented the Na+-sensitive phenotype of an Escherichia coli mutant that is deficient in Na+/H+ antiport activity (strain KNabc). GerN also reduced the concentration of K+ required to support growth of an E. coli mutant deficient in K+ uptake (strain TK2420). In a fluorescence-based assay of evertedE. coli KNabc membrane vesicles, GerN exhibited robust Na+/H+ antiport activity, with a Km for Na+ estimated at 1.5 mM at pH 8.0 and 25 mM at pH 7.0. Li+, but not K+, served as a substrate. GerN-mediated Na+/H+ antiport was further demonstrated in everted vesicles as energy-dependent accumulation of 22Na+. GerN also used K+ as a coupling ion without completely replacing H+, as indicated by partial inhibition by K+ of H+ uptake into right-side-out vesicles loaded with Na+. K+translocation as part of the antiport was supported by the stimulatory effect of intravesicular K+ on22Na+ uptake by everted vesicles and the dependence of GerN-mediated86Rb+ efflux on the presence of Na+ in trans. The inhibitory patterns of protonophore and thiocyanate were most consistent with an electrogenic Na+/H+-K+antiport. GerN-mediated Na+/H+-K+antiport was much more rapid than GerN-mediated Na+/H+ antiport.

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9

Jin, Jie, Arthur A. Guffanti, Catherine Beck und Terry A. Krulwich. „Twelve-Transmembrane-Segment (TMS) Version (ΔTMS VII-VIII) of the 14-TMS Tet(L) Antibiotic Resistance Protein Retains Monovalent Cation Transport Modes but Lacks Tetracycline Efflux Capacity“. Journal of Bacteriology 183, Nr. 8 (15.04.2001): 2667–71. http://dx.doi.org/10.1128/jb.183.8.2667-2671.2001.

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ABSTRACT A “Tet(L)-12” version of Tet(L), a tetracycline efflux protein with 14 transmembrane segments (TMS), was constructed by deletion of two central TMS. Tet(L)-12 catalyzed Na+/H+antiport and antiport with K+ as a coupling ion as well as or better than wild-type Tet(L) but exhibited no tetracycline-Me2+/H+ antiport inEscherichia coli vesicles.

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10

Incerpi, S., S. Spagnuolo, F. Terenzi und S. Leoni. „EGF modulation of Na+/H+ antiport in rat hepatocytes: different sensitivity in adult and fetal cells“. American Journal of Physiology-Cell Physiology 270, Nr. 3 (01.03.1996): C841—C847. http://dx.doi.org/10.1152/ajpcell.1996.270.3.c841.

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The modulation by epidermal growth factor (EGF) of the Na+/H+ antiport in fetal and adult rat hepatocytes was studied in nominally HCO3- free solution. EGF (10 nM) activated the antiport in adult rat hepatocytes by 0.22 +/- 0.03 (mean +/- SD;n=10) pH units over basal value, measured with the fluorescent pH-sensitive intracellular probe, 2',7'-bis(carboxyethyl)-5(6)- carboxyfluorescein (BCECF). The effect of EGF was inhibited by amiloride analogue 5-(N-ethyl-N-isopropyl) amiloride (EIPA), by ouabain, inhibitor of the Na+ pump, and by erbstatin analogue, an inhibitor of the tyrosine kinase activity of the EGF receptor. The effect of EGF on Na+/H+ antiport in adult rat hepatocytes appeared to be mediated by both protein kinase C (PKC) and G protein system. No effect of EGF and phorbol 12-myristate 13-acetate, an activator of PKC, on the Na+/H+ antiport was observed in fetal hepatocytes of 20 and 22 days. A different sensitivity of the antiport to high concentrations of amiloride and EIPA suggests that altered amount of the Na+/H+ antiport units or different isoforms could be expressed in fetal compared with adult cells.

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11

Puceat, M., O. Clement-Chomienne, A. Terzic und G. Vassort. „Alpha 1-adrenoceptor and purinoceptor agonists modulate Na-H antiport in single cardiac cells“. American Journal of Physiology-Heart and Circulatory Physiology 264, Nr. 2 (01.02.1993): H310—H319. http://dx.doi.org/10.1152/ajpheart.1993.264.2.h310.

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We investigated the effects of an alpha 1-adrenoceptor (phenylephrine) and a purinoceptor agonist (ATP), both of which accelerate the phosphoinositide turnover, on the Na-H antiport activity of rat single cardiac cells using the pH-sensitive fluorescent indicator seminaphthorhodafluor-1 (SNARF-1). Both phenylephrine, in the presence of a beta-adrenoceptor blocker, and ATP enhanced the ability of the cell to regulate its intracellular pH (pHi) after an imposed acid load. This effect was observed in HCO3-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) and prevented by Na-H antiport inhibitors ethylisopropylamiloride (EIPA) or amiloride. Similar results were obtained when cells were bathed in an acidic extracellular medium. Hence, the alpha 1-adrenoceptor and purinoceptor agonists activate the Na-H antiport even when it is partially inhibited by extracellular protons. To further evaluate the effects of the two neurohormones, the rate of proton efflux was estimated as a function of the magnitude of the imposed acid load. The results indicate that the agonist-induced modulation of the Na-H antiport is caused by an acceleration of its exchange activity and by a shift of its dependence on pHi toward more alkaline pH values. The agonist-mediated stimulation of the antiport was also observed in partially depolarized cells and was not dependent on intracellular Ca. Phorbol 12-myristate 13-acetate was not able to reproduce the effects of the agonists on the Na-H antiport. Conversely, the inhibitors of protein kinase C did not prevent the activation of the antiport by the neurohormones. Thus our data suggest that neither a Ca-calmodulin-dependent kinase nor protein kinase C is responsible for the alpha 1-adrenoceptor- and purinoceptor-mediated stimulation of the antiport.

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12

Sastrasinh, M., P. Young, E. J. Cragoe und S. Sastrasinh. „The Na+/H+ antiport in renal mitochondria“. American Journal of Physiology-Cell Physiology 268, Nr. 5 (01.05.1995): C1227—C1234. http://dx.doi.org/10.1152/ajpcell.1995.268.5.c1227.

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In isolated renal mitochondria, Na+ and Li+ stimulated H+ efflux from the mitochondrial matrix. In submitochondrial particles (SMP), Na+ flux was also coupled to H+ transport in the opposite direction. The overshoot of Na+ uptake in SMP with an outwardly directed H+ gradient indicated that downhill efflux of H+ through the mitochondrial membrane induced uphill transport of Na+. Similar to the Na+/H+ antiport in other types of mitochondria, the antiport in renal mitochondria was more sensitive to amiloride derivatives than to amiloride itself. Benzamil and ethylisopropylamiloride (EIPA), but not amiloride, inhibited the antiport, with 50% inhibition of 10(-4) M for both benzamil in mitochondria and EIPA in SMP. The Na+/H+ antiport in renal mitochondria had simple saturation kinetics for external Na+ [Michaelis-Menten constant (Km) = 3.27 +/- 0.63 mM; maximal velocity (Vmax) = 0.022 +/- 0.002 pH units/s] and Li+ (Km = 3.62 +/- 0.75 mM; Vmax = 0.022 +/- 0.002 pH units/s). NH4Cl and NH4 acetate stimulated Na+ efflux and inhibited Na+ uptake in SMP. Comparable results with NH4 acetate and chloride suggested that NH4+ modified Na+ transport through its direct interaction with the Na+/H+ antiport, rather than through the alkalinization of intra-SMP space from non-ionic diffusion of NH3. These results suggested that the Na+/H+ antiport may be a factor in the exit of NH4+ from renal mitochondria.

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Jung, Dennis W., und Gerald P. Brierley. „Matrix free Mg2+ and the regulation of mitochondrial volume“. American Journal of Physiology-Cell Physiology 277, Nr. 6 (01.12.1999): C1194—C1201. http://dx.doi.org/10.1152/ajpcell.1999.277.6.c1194.

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Mitochondria must maintain volume homeostasis in order to carry out oxidative phosphorylation. It has been postulated that the concentration of free Mg2+([Mg2+]) serves as the sensor of matrix volume and regulates a K+-extruding K+/H+antiport (K. D. Garlid. J. Biol. Chem. 255: 11273–11279, 1980). To test this hypothesis, the fluorescent probe furaptra was used to monitor [Mg2+] and free Ca2+ concentration ([Ca2+]) in the matrix of isolated beef heart mitochondria, and K+/H+antiport activity was measured by passive swelling in potassium acetate. Concentrations that result in 50% inhibition of maximum activity of 92 μM matrix [Mg2+] and 2.2 μM [Ca2+] were determined for the K+/H+ antiport. Untreated mitochondria average 670 μM matrix [Mg2+], a value that would permit <1% of maximum K+/H+antiport activity. Hypotonic swelling results in large decreases in matrix [Mg2+], but swelling due to accumulation of acetate salts does not alter [Mg2+]. Swelling in phosphate salts decreases matrix [Mg2+], but not to levels that permit appreciable antiport activity. We conclude that 1) it is unlikely that matrix [Mg2+] serves as the mitochondrial volume sensor, 2) if K+/H+antiport functions as a volume control transporter, it is probably regulated by factors other than [Mg2+], and 3) alternative mechanisms for mitochondrial volume control should be considered.

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Davies, J. E., und L. L. Ng. „Simvastatin and Intracellular pH Regulation by the Na+/H+ Antiport of Sv40-Virus-Transformed Human Mrc5 Fibroblasts“. Clinical Science 84, Nr. 6 (01.06.1993): 633–43. http://dx.doi.org/10.1042/cs0840633.

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1. Inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase by simvastatin leads to inhibition of both cell growth and Na+/H+ antiport activity. The effect of simvastatin on intracellular pH and Na+/H+ antiport activity was therefore studied on an adherent cell line, the SV40-virus-transformed MRC5 human fibroblast. 2. Simvastatin led to a dose-dependent decrease in intracellular pH, attributed to a reduction in Na+/H+ exchange, together with a rounding of cell shape. Mevalonate (1 mmol/l) prevented these effects of simvastatin, and when added after inhibition of the antiport by simvastatin, reversed these changes within 1–2 h. 3. The phenomenon of mevalonate reversal of anti-port inhibition by simvastatin was not sensitive to cycloheximide, indicating its post-translational nature. This was also consistent with the short period of incubation with mevalonate leading to reversal of antiport inhibition (1-2h). These changes in intracellular pH regulation were not due to alterations in cell cholesterol content. 4. A variety of inhibitors of post-translational processes, such as N-linked glycosylation (tunicamycin), phosphorylation (staurosporine), isoprenylation (farnesol, limonene), and of pertussis-toxin-sensitive G-proteins or calmodulin (W7), had no effect on the reversal by mevalonate of simvastatin-induced changes in Na+/H+ antiport activity. 5. N-Ethylmaleimide (50 μmol/l for 5 min) prevented mevalonate reversing the effects of simvastatin, suggesting the importance of thiol groups in the phenomenon of reversal of the inhibition of Na+/H+ antiport activity by simvastatin. Furthermore, concurrent incubation of simvastatin-treated cells with dithiothreitol (1 mmol/l) and N-ethylmaleimide restored the ability of mevalonate to reverse the inhibitory effects of simvastatin on Na+H+ antiport activity.

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Mitchell, Claire H., Johannes C. Fleischhauer, W. Daniel Stamer, K. Peterson-Yantorno und Mortimer M. Civan. „Human trabecular meshwork cell volume regulation“. American Journal of Physiology-Cell Physiology 283, Nr. 1 (01.07.2002): C315—C326. http://dx.doi.org/10.1152/ajpcell.00544.2001.

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The volume of certain subpopulations of trabecular meshwork (TM) cells may modify outflow resistance of aqueous humor, thereby altering intraocular pressure. This study examines the contribution that Na+/H+, Cl−/HCO[Formula: see text]exchange, and K+-Cl− efflux mechanisms have on the volume of TM cells. Volume, Cl− currents, and intracellular Ca2+ activity of cultured human TM cells were studied with calcein fluorescence, whole cell patch clamping, and fura 2 fluorescence, respectively. At physiological bicarbonate concentration, the selective Na+/H+ antiport inhibitor dimethylamiloride reduced isotonic cell volume. Hypotonicity triggered a regulatory volume decrease (RVD), which could be inhibited by the Cl− channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), the K+channel blockers Ba2+ and tetraethylammonium, and the K+-Cl− symport blocker [(dihydroindenyl)oxy]alkanoic acid. The fluid uptake mechanism in isotonic conditions was dependent on bicarbonate; at physiological levels, the Na+/H+ exchange inhibitor dimethylamiloride reduced cell volume, whereas at low levels the Na+-K+-2Cl− symport inhibitor bumetanide had the predominant effect. Patch-clamp measurements showed that hypotonicity activated an outwardly rectifying, NPPB-sensitive Cl− channel displaying the permeability ranking Cl− > methylsulfonate > aspartate. 2,3-Butanedione 2-monoxime antagonized actomyosin activity and both increased baseline [Ca2+] and abolished swelling-activated increase in [Ca2+], but it did not affect RVD. Results indicate that human TM cells display a Ca2+-independent RVD and that volume is regulated by swelling-activated K+ and Cl− channels, Na+/H+ antiports, and possibly K+-Cl− symports in addition to Na+-K+-2Cl− symports.

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Rotin, D., und S. Grinstein. „Impaired cell volume regulation in Na(+)-H+ exchange-deficient mutants“. American Journal of Physiology-Cell Physiology 257, Nr. 6 (01.12.1989): C1158—C1165. http://dx.doi.org/10.1152/ajpcell.1989.257.6.c1158.

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To elucidate the mechanism of regulatory volume increase (RVI) in Chinese hamster ovary cells, Na(+)-H+ exchange-deficient mutants, called AP-1, were derived from WT-5 cells, a wildtype subclone. The absence of functional antiports in AP-1 cells was established through measurements of intracellular pH (pHi) and Na+ uptake. Cells exposed to hypotonic medium initially swelled but regained near-normal volume within minutes. When isotonicity was then restored, WT-5 cells shrank immediately and then carried out RVI, which was inhibited by 0.1 mM amiloride. This amiloride-sensitive RVI was absent in the AP-1 mutants, suggesting involvement of Na(+)-H+ exchange. In some cell types, RVI is mediated by Na(+)-K(+)-2Cl- cotransport. Bumetanide-sensitive 86Rb+ (K+) influx was detectable in both WT-5 and AP-1 cells, suggesting the presence of Na(+)-K(+)-2Cl- cotransport. Bumetanide-sensitive influx was stimulated by osmotic shrinking in WT-5 cells, and only slightly in AP-1 cells. However, Na(+)-K(+)-2Cl- cotransport did not contribute to volume regulation, since bumetanide (50 microM) failed to inhibit RVI in osmotically shrunken WT-5 cells. The inability of cotransport to induce a volume gain in WT-5 cells was attributable to the simultaneous stimulation of Na(+)-K(+)-2Cl- efflux. The rate of efflux was similar in magnitude to the corresponding influx rate so that net Na(+)-K(+)-2Cl- cotransport was negligible. These results show that RVI in osmotically shrunken Chinese hamster ovary cells is mediated by the Na(+)-H+ antiport and that, although stimulated, Na(+)-K(+)-2Cl- cotransport does not contribute to anisosmotic volume regulation.

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Civan, M. M., E. J. Cragoe und K. Peterson-Yantorno. „Intracellular pH in frog skin: effects of Na+, volume, and cAMP“. American Journal of Physiology-Renal Physiology 255, Nr. 1 (01.07.1988): F126—F134. http://dx.doi.org/10.1152/ajprenal.1988.255.1.f126.

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Single skins were analyzed by 31P-nuclear magnetic resonance (NMR) spectroscopy during alternate perfusion with control and experimental solutions. Intracellular (pHc) and extracellular (pHo) pH were monitored by measuring the spectral frequencies of intracellular Pi and external methylphosphonate, respectively. Base-line pHc was 7.20 +/- 0.02 (SE) when pHo was 6.99 +/- 0.02. A 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS)-inhibitable, HCO3--dependent alkaline shift in pHc can be elicited by replacing external Cl- by gluconate or sulfate. We now report that this effect is observed even in sodium-free media. The substitution of gluconate for external Cl- has also been reported to shrink cell volume. This shrinkage can be minimized by replacing Cl- with gluconate during perfusion with hypotonic, rather than isotonic, media. Conducted in this manner, the anionic substitution produces a much smaller alkaline shift in pHc. Replacement of external NaCl with N-methyl-D-glucamine chloride acidified the cells reversibly by 0.22 +/- 0.02. In the presence of the Na-H antiport blocker 5-(N-methyl-N-isobutyl)amiloride (MIA), restoration of external Na+ did not increase pHc. Separate addition of MIA acidified the cells by 0.18 +/- 0.03. Adenosine 3',5'-cyclic monophosphate (cAMP) also alters pHc. Addition of 1 mM 8(4-chlorophenylthio)cAMP or 100 mU/ml vasopressin acidified the cells by 0.22 +/- 0.03 and by 0.14 +/- 0.04, respectively. The data suggest that frog skin regulates pHc by the parallel operation of Na-H and Na+-independent Cl-HCO3 antiports. Cell volume and cAMP may play regulating roles in this epithelium.

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HENDRICH, LARS, und CHRIS H. S. WATTS. „An endemic predaceous water beetle from the Murchison River in Western Australia—Antiporus kalbarriensis sp.n. (Coleoptera: Dytiscidae, Hydroporinae, Hydroporini)“. Zootaxa 2338, Nr. 1 (19.01.2010): 35. http://dx.doi.org/10.11646/zootaxa.2338.1.3.

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Antiporus kalbarriensis sp.n. is described from the Murchison bioregion in Western Australia. The species appears to be restricted to backwater pools and oxbows along the Murchison River. Morphologically it is near Antiporus bakewellii (Clark, 1862) (Queensland, New South Wales), A. jenniferae Watts, 1997 (Northern Territory, N Queensland, NW Australia) and A. simplex Watts, 1978 (Queensland) but differs by the form of the median lobe, size and male proclaw. The habitat and its water beetle coenosis are described in detail. Additional distributional records for A. bakewellii and A. jenniferae are given. Altogether 15 species of Antiporus are now reported from Australia. The new species underline the importance of south-western Australia as a hotspot of diversity for Dytiscidae of the tribe Hydroporini Aubé, 1836.

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Gunby, Phil. „Worldwide Antipolio Campaign Strategy Evolving“. JAMA: The Journal of the American Medical Association 267, Nr. 4 (22.01.1992): 479. http://dx.doi.org/10.1001/jama.1992.03480040027004.

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Gunby, P. „Worldwide antipolio campaign strategy evolving“. JAMA: The Journal of the American Medical Association 267, Nr. 4 (22.01.1992): 479a—479. http://dx.doi.org/10.1001/jama.267.4.479a.

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Robinson, Anne E., Nathan E. Thomas, Emma A. Morrison, Bryan M. Balthazor und Katherine A. Henzler-Wildman. „New free-exchange model of EmrE transport“. Proceedings of the National Academy of Sciences 114, Nr. 47 (07.11.2017): E10083—E10091. http://dx.doi.org/10.1073/pnas.1708671114.

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EmrE is a small multidrug resistance transporter found in Escherichia coli that confers resistance to toxic polyaromatic cations due to its proton-coupled antiport of these substrates. Here we show that EmrE breaks the rules generally deemed essential for coupled antiport. NMR spectra reveal that EmrE can simultaneously bind and cotransport proton and drug. The functional consequence of this finding is an exceptionally promiscuous transporter: not only can EmrE export diverse drug substrates, it can couple antiport of a drug to either one or two protons, performing both electrogenic and electroneutral transport of a single substrate. We present a free-exchange model for EmrE antiport that is consistent with these results and recapitulates ∆pH-driven concentrative drug uptake. Kinetic modeling suggests that free exchange by EmrE sacrifices coupling efficiency but boosts initial transport speed and drug release rate, which may facilitate efficient multidrug efflux.

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22

Mackovic-Basic, M., L. G. Fine, J. T. Norman, E. J. Cragoe und I. Kurtz. „Stimulation of Na+/H+ exchange is not required for induction of hypertrophy of renal cells in vitro.“ Journal of the American Society of Nephrology 3, Nr. 5 (November 1992): 1124–30. http://dx.doi.org/10.1681/asn.v351124.

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Hypertrophy of renal proximal tubular cells is associated with an early increase in Na+/H+ antiport activity both in vivo and in vitro. The purpose of the study presented here was to determine whether functioning Na+/H+ antiport activity is required for hypertrophy to occur. LLC-PK1 cells deficient in Na+/H+ antiport activity were prepared by the "proton-suicide" method. Mutant cells had 28 to 40% of the normal Na+/H+ antiport activity. The addition of 50 nM methylisobutylamiloride to these cells decreased the antiport activity to less than 5% of the control value. In the mutant cells, steady-state intracellular pH was normal as was the protein content. After exposure of the wild-type cells for 72 h to 10(-6) M insulin and 10(-9) M insulin-like growth factor 1, cell protein content increased significantly. The increase in protein content induced by these growth factors in the mutant cells did not differ significantly from the response of the wild-type cells. Lowering the Na+/H+ exchange further by the addition of methylisobutylamiloride (50 nM) to less than 5% of the control value did not blunt the hypertrophic response in the mutant cells. These studies indicate that hypertrophy can be induced in LLC-PK1 cells by growth factors when basal Na+/H+ antiport activity is reduced to low levels by selective mutation or by competitive inhibition. The results suggest that stimulation of the Na+/H+ antiporter is not an essential prerequisite for the induction of hypertrophy in renal cells.

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Ricci, R., P. Baldini, L. Bogetto, P. De Vito, P. Luly, A. Zannetti und S. Incerpi. „Dual modulation of Na/H antiport by atrial natriuretic factor in rat aortic smooth muscle cells“. American Journal of Physiology-Cell Physiology 273, Nr. 2 (01.08.1997): C643—C652. http://dx.doi.org/10.1152/ajpcell.1997.273.2.c643.

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The aim of the present work was to study the effect of the atrial natriuretic factor (ANF) on the Na/H antiport in rat aorta smooth muscle cells, evaluated as intracellular pH (pHi) recovery after an acid load with ammonium chloride. The Na/H antiport was studied using a fluorescent probe, sensitive to pHi, 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Our data indicate that ANF modulates the activity of the Na/H antiport in both a dose- and time-dependent manner. Hormone concentrations of 10(-10) M activate the antiport, increasing both the rate of recovery and the set point by approximately 0.2 pH units. This effect is mediated by diacylglycerol as a result of phospholipid hydrolysis by a phospholipase C, even if an involvement of adenosine 3',5'-cyclic monophosphate (cAMP) cannot be ruled out. ANF (10(-7) M) inhibits the antiport, decreasing both the rate of recovery and the set point by approximately 0.3 pH units, because of guanosine 3',5'-cyclic monophosphate production. Both inhibition and stimulation of pHi by ANF were more pronounced when the hormone was given before the acid load, perhaps because of the longer time exposure. We present new hypotheses on the mechanism of action of this paracrine/autocrine factor.

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24

Grinstein, S., S. Cohen, J. D. Goetz und A. Rothstein. „Osmotic and phorbol ester-induced activation of Na+/H+ exchange: possible role of protein phosphorylation in lymphocyte volume regulation.“ Journal of Cell Biology 101, Nr. 1 (01.07.1985): 269–76. http://dx.doi.org/10.1083/jcb.101.1.269.

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The Na+/H+ antiport is stimulated by 12-O-tetradecanoylphorbol-13, acetate (TPA) and other phorbol esters in rat thymic lymphocytes. Mediation by protein kinase C is suggested by three findings: (a) 1-oleoyl-2-acetylglycerol also activated the antiport; (b) trifluoperazine, an inhibitor of protein kinase C, blocked the stimulation of Na+/H+ exchange; and (c) activation of countertransport was accompanied by increased phosphorylation of specific membrane proteins. The Na+/H+ antiport is also activated by osmotic cell shrinking. The time course, extent, and reversibility of the osmotically induced and phorbol ester-induced responses are similar. Moreover, the responses are not additive and they are equally susceptible to inhibition by trifluoperazine, N-ethylmaleimide, and ATP depletion. The extensive analogies between the TPA and osmotically induced effects suggested a common underlying mechanism, possibly activation of a protein kinase. It is conceivable that osmotic shrinkage initiates the following sequence of events: stimulation of protein kinase(s) followed by activation of the Na+/H+ antiport, resulting in cytoplasmic alkalinization. The Na+ taken up through the antiport, together with the HCO3- and Cl- accumulated in the cells as a result of the cytoplasmic alkalinization, would be followed by osmotically obliged water. This series of events could underlie the phenomenon of regulatory volume increase.

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Ng, L. L., und J. E. Davies. „HMG CoA reductase inhibitors affect Na(+)-H+ antiport activity in human lymphoblasts“. American Journal of Physiology-Cell Physiology 261, Nr. 5 (01.11.1991): C780—C786. http://dx.doi.org/10.1152/ajpcell.1991.261.5.c780.

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The Na(+)-H+ antiport is a membrane-bound glycoprotein that extrudes intracellular acid loads and regulates cellular volume. Cellular synthesis of the oligosaccharide side chains of glycoproteins is dependent on a supply of mevalonate, itself a product of the rate-limiting enzyme of cholesterol synthesis 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase. The effect of two HMG CoA reductase inhibitors (simvastatin and 25-hydroxycholesterol) on intracellular pH and Na(+)-H+ exchange was therefore studied. Inhibition of the Na(+)-H+ antiport by these agents led to a fall in intracellular pH but did not impair the regulatory volume increase response to a hypertonic stimulus. The inhibitory effect of simvastatin was prevented by mevalonate but not dolichol or squalene. The effect of 25-hydroxycholesterol was more complex and not easily reversed. Thus HMG CoA reductase inhibitors reduced the ability of human lymphoblasts to expel an intracellular acid load via the Na(+)-H+ antiport, although the response of the antiport to an osmotic stimulus was preserved.

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Dudley, C. R. K., D. J. Taylor, L. L. Ng, G. J. Kemp, P. J. Ratcliffe, G. K. Radda und J. G. G. Ledingham. „Evidence for Abnormal Na+/H+ Antiport Activity Detected by Phosphorus Nuclear Magnetic Resonance Spectroscopy in Exercising Skeletal Muscle of Patients with Essential Hypertension“. Clinical Science 79, Nr. 5 (01.11.1990): 491–97. http://dx.doi.org/10.1042/cs0790491.

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1. Exercise-induced pH changes in skeletal muscle were studied in a group of eight subjects with essential hypertension by using 31P n.m.r. spectroscopy. 2. Leucocyte Na+/H+ antiport activity was measured in vitro in the same subjects using a pH-sensitive fluorescent dye. 3. Resting skeletal muscle pH and unstimulated leucocyte pH values were similar to those in control subjects, but increased Na+/H+ antiport activity was demonstrated in the leucocytes from hypertensive subjects by acid loading in vitro. Decreased skeletal muscle acidification and an increased rate of pH recovery was also demonstrated in vivo in these same patients during an acid load induced by isotonic exercise. 4. These findings suggest that the increased cellular Na+/H+ antiport activity, which has been demonstrated in vitro in essential hypertension, also affects the biochemical response of skeletal muscle to physiological levels of exercise. This strengthens the argument that increased Na+/H+ antiport activity in hypertension is a generalized and physiologically relevant cellular abnormality.

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27

Swartz, Talia H., Masahiro Ito, Takayuki Ohira, Shinsuke Natsui, David B. Hicks und Terry A. Krulwich. „Catalytic Properties of Staphylococcus aureus and Bacillus Members of the Secondary Cation/Proton Antiporter-3 (Mrp) Family Are Revealed by an Optimized Assay in an Escherichia coli Host“. Journal of Bacteriology 189, Nr. 8 (09.02.2007): 3081–90. http://dx.doi.org/10.1128/jb.00021-07.

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ABSTRACT Monovalent cation proton antiporter-3 (Mrp) family antiporters are widely distributed and physiologically important in prokaryotes. Unlike other antiporters, they require six or seven hydrophobic gene products for full activity. Standard fluorescence-based assays of Mrp antiport in membrane vesicles from Escherichia coli transformants have not yielded strong enough signals for characterization of antiport kinetics. Here, an optimized assay protocol for vesicles of antiporter-deficient E. coli EP432 transformants produced higher levels of secondary Na+(Li+)/H+ antiport than previously reported. Assays were conducted on Mrps from alkaliphilic Bacillus pseudofirmus OF4 and Bacillus subtilis and the homologous antiporter of Staphylococcus aureus (Mnh), all of which exhibited Na+(Li+)/H+ antiport. A second paralogue of S. aureus (Mnh2) did not. K+, Ca2+, and Mg2+ did not support significant antiport by any of the test antiporters. All three Na+(Li+)/H+ Mrp antiporters had alkaline pH optima and apparent Km values for Na+ that are among the lowest reported for bacterial Na+/H+ antiporters. Using a fluorescent probe of the transmembrane electrical potential (ΔΨ), Mrp Na+/H+ antiport was shown to be ΔΨ consuming, from which it is inferred to be electrogenic. These assays also showed that membranes from E. coli EP432 expressing Mrp antiporters generated higher ΔΨ levels than control membranes, as did membranes from E. coli EP432 expressing plasmid-borne NhaA, the well-characterized electrogenic E. coli antiporter. Assays of respiratory chain components in membranes from Mrp and control E. coli transformants led to a hypothesis explaining how activity of secondary, ΔΨ-consuming antiporters can elicit increased capacity for ΔΨ generation in a bacterial host.

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Grinstein, S., A. Rothstein und S. Cohen. „Mechanism of osmotic activation of Na+/H+ exchange in rat thymic lymphocytes.“ Journal of General Physiology 85, Nr. 5 (01.05.1985): 765–87. http://dx.doi.org/10.1085/jgp.85.5.765.

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The activity of the Na+/H+ exchange system of rat thymic lymphocytes was determined by means of intracellular (pHi) and extracellular pH (pH0) measurements. In isotonic media, the antiport is virtually quiescent at physiological pHi (7.0-7.1), but is greatly activated by cytoplasmic acidification. At normal pHi, the antiport can also be activated by osmotic shrinking. Osmotic activation occurs after a delay of 20-30 s and is reversed several minutes after iso-osmolarity is restored. The mechanism of activation was analyzed by comparing the kinetic parameters of transport in resting (isotonic) and hyperosmotically stressed cells. The affinities of the external substrate site for Na+ and H+ are not altered in shrunken cells. In contrast, the Hi+ sensitivity of the antiport (which is largely dictated by an allosteric modifier site) was increased, which accounted for the activation. The concentration of free cytoplasmic Ca2+ [( Ca2+]i) increased after osmotic shrinking. This increase was dependent on the presence of extracellular Ca2+ and Na+ and was blocked by inhibitors of Na+/H+ exchange, which suggests that it is a consequence, rather than the cause, of the activation of the antiport. It is concluded that the shift in the pHi dependence of the modifier site of the Na+/H+ antiport is the primary event underlying the regulatory volume increase that follows osmotic shrinkage.

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Church, J. G., G. B. Mills und R. N. Buick. „Activation of the Na+/H+ antiport is not required for epidermal growth factor-dependent gene expression, growth inhibition or proliferation in human breast cancer cells“. Biochemical Journal 257, Nr. 1 (01.01.1989): 151–57. http://dx.doi.org/10.1042/bj2570151.

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Mitogen interaction with specific receptors in many cell types leads to activation of the Na+/H+ antiport and a resultant cytoplasmic alkalinization. Since amiloride inhibits both Na+/H+ exchange and cell proliferation, it has been hypothesized that activation of the antiport is an obligatory requirement for mitogenesis. However, concentrations of amiloride which inhibit the antiport also inhibit other cellular processes, including protein synthesis and phosphorylation. We have used an epidermal growth factor (EGF) receptor gene-amplified human breast cancer cell line, the growth of which is inhibited by high levels of EGF in culture (MDA-468) and a variant, the growth of which is stimulated by EGF (MDA-468-S4), along with two potent amiloride analogues to examine whether activation of the Na+/H+ antiport and cytoplasmic alkalinization is necessary for both EGF-dependent effects to occur. At concentrations of the amiloride analogues which block Na+/H+ exchange in both cell types by 76-98%, the EGF-dependent alterations in [3H]thymidine incorporation or induction in c-myc or c-fos gene transcription were unaltered. These results were confirmed by a lack of effect of the amiloride analogues on both the growth-stimulatory and growth-inhibitory effects on EGF in an anchorage-independent growth assay. Similarly, in pH-altered media that prevented normal cytoplasmic alkalinization, the response of both MDA-468 and MDA-468-S4 to EGF activation was unaltered. In addition, activation of the Na+/H+ antiport alone was not sufficient to induce c-myc and c-fos transcription in either cell type. Taken together, these data suggest that neither the Na+/H+ antiport nor cytoplasmic alkalinization are necessary or sufficient for either EGF-dependent growth stimulation or growth inhibition in MDA-468 human breast cancer cells.

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Vallance, S. J., C. P. Downes, E. J. Cragoe und A. D. Whetton. „Granulocyte-macrophage colony-stimulating factor can stimulate macrophage proliferation via persistent activation of Na+/H+ antiport. Evidence for two distinct roles for Na+/H+ antiport activation“. Biochemical Journal 265, Nr. 2 (15.01.1990): 359–64. http://dx.doi.org/10.1042/bj2650359.

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Macrophages respond to a variety of extracellular stimuli which can modulate the proliferation, development, activation and functional activity of these cells. The effects of two such agents, granulocytemacrophage colony-stimulating factor (GM-CSF, which stimulates proliferation) and platelet-activating factor (PAF, which stimulates chemotaxis and bactericidal activity), on cellular signal transduction mechanisms were compared. PAF can stimulate inositol lipid hydrolysis leading to Ca2+ mobilization. GM-CSF on the other hand has no effect on these events. Both agonists do, however, share an ability to activate an amiloride-sensitive Na+/H+ antiport and, furthermore, amiloride analogues are shown to inhibit the proliferative effects of GM-CSF on these cells. Long-term incubations with either PAF or GM-CSF demonstrate that it is only those cells pretreated with the latter which show a persistent activation of the antiport together with a sustained increase in intracellular pH. PAF-treated cells exhibit only a transitory increase in antiport activity, their intracellular pH levels returning to resting levels in spite of the continuous presence of the agonist in the medium. These effects of GM-CSF and PAF on Na+/H+ exchange are observed in both bicarbonate-free and bicarbonate-containing medium. These results lead us to suggest that the Na+/H+ antiport has a role in macrophage proliferation and in the regulation of intracellular pH during the oxidative burst stimulated by PAF and other agonists, and that differential mechanisms whereby this antiport is regulated exist in macrophages.

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Cutaia, M., K. Tollefson, J. Kroczynski, N. Parks und S. Rounds. „Role of the Na/H antiport in pH-dependent cell death in pulmonary artery endothelial cells“. American Journal of Physiology-Lung Cellular and Molecular Physiology 278, Nr. 3 (01.03.2000): L536—L544. http://dx.doi.org/10.1152/ajplung.2000.278.3.l536.

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We investigated the role of intracellular pH (pHi) and Na/H exchange in cell death in human pulmonary artery endothelial cells (HPAEC) following a metabolic insult (inhibition-oxidative phosphorylation, glycolysis). Metabolic inhibition in medium at pH 7.4 decreased viability (0–15% live cells) over 6 h. Cell death was attenuated by maneuvers that decreased pHi and inhibited Na/H exchange (acidosis, Na/H antiport inhibitors). In contrast, cell death was potentiated by maneuvers that elevated pHi or increased Na/H exchange (monensin, phorbol ester treatment) before the insult. HPAEC demonstrated a biphasic pHi response following a metabolic insult. An initial decrease in pHi was followed by a return to baseline over 60 min. Maneuvers that protected HPAEC and inhibited Na/H exchange (acidosis, Na+-free medium, antiport inhibitors) altered this pattern. pHi decreased, but no recovery was observed, suggesting that the return of pHi to normal was mediated by antiport activation. Although Na/H antiport activity was reduced (55–60% of control) following a metabolic insult, the cells still demonstrated active Na/H exchange despite significant ATP depletion. Phorbol ester pretreatment, which potentiated cell death, increased Na/H antiport activity above the level observed in monolayers subjected to a metabolic insult alone. These results demonstrate that HPAEC undergo a pH-dependent loss of viability linked to active Na/H exchange following a metabolic insult. Potentiation of cell death with phorbol ester treatment suggests that this cell death pathway involves protein kinase C-mediated phosphorylation events.

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Hensley, C. B., M. E. Bradley und A. K. Mircheff. „Parathyroid hormone-induced translocation of Na-H antiporters in rat proximal tubules“. American Journal of Physiology-Cell Physiology 257, Nr. 4 (01.10.1989): C637—C645. http://dx.doi.org/10.1152/ajpcell.1989.257.4.c637.

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Parathyroid hormone (PTH) is believed to inhibit bicarbonate reabsorption by inhibiting Na-H antiport activity in proximal tubular brush-border membranes. The sequence of events triggered by PTH was investigated in a crude preparation of proximal tubules obtained by mechanical disruption and filtration through nylon mesh filters. Tubule samples were subjected to analytical subcellular fractionation after 2-, 5-, and 30-min treatments with 1 IU/ml PTH. These PTH-treatment intervals caused 54, 63, and 68% decreases in the Na-H antiport activity of a population of brush-border membrane vesicles that was resolved from a PTH-unresponsive brush-border population by density-gradient centrifugation. The rapid loss of Na-H antiport activity from the responsive population was accompanied by a transient increase in the Na-H antiport activity of a region of the density gradient, designated density window III, which was shown to contain two distinct membrane populations; these populations were both enriched in acid phosphatase activity, and one of them was also an important locus of galactosyltransferase activity. The increase in the Na-H antiport activity of window III accounted for 52% of the activity lost from the PTH-responsive population after 2 min, and for 43% of the activity lost after 5 min, but it was completely abolished after 25 more minutes in the presence of PTH. These observations suggest that PTH triggers a rapid translocation of Na-H antiporters from the microvillus membrane to a distinct membrane domain, where they are subsequently inactivated.

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Poolman, B. „Precursor/product antiport in bacteria“. Molecular Microbiology 4, Nr. 10 (Oktober 1990): 1629–36. http://dx.doi.org/10.1111/j.1365-2958.1990.tb00539.x.

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Frisco, Pierluigi. „P systems with symport-antiport“. Scholarpedia 6, Nr. 10 (2011): 11704. http://dx.doi.org/10.4249/scholarpedia.11704.

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Brierley, Gerald P., und Dennis W. Jung. „K+/H+ antiport in mitochondria“. Journal of Bioenergetics and Biomembranes 20, Nr. 2 (April 1988): 193–209. http://dx.doi.org/10.1007/bf00768394.

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Zhang, Siyun, Ming Cheng, Manivannan Kalavathi Dhinakaran, Yue Sun und Haibing Li. „Enantioselective Antiport in Asymmetric Nanochannels“. ACS Nano 15, Nr. 8 (28.07.2021): 13148–54. http://dx.doi.org/10.1021/acsnano.1c02630.

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37

Alarie, Yves, und Chris H. S. Watts. „Larvae of the genus Antiporus (Coleoptera : Dytiscidae) and phylogenetic implications“. Invertebrate Systematics 18, Nr. 5 (2004): 523. http://dx.doi.org/10.1071/is03025.

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The larvae of Antiporus blakeii (Clark), A. femoralis (Boheman), A. gilbertii (Clark), A. hollingsworthi Watts, A. jenniferae Watts, A. uncifer Sharp and A. willyamsi Watts are described with an emphasis on chaetotaxy of the head capsule, head appendages, legs, last abdominal segment and urogomphi. A parsimony analysis based on 17 informative larval characteristics was conducted using the program PAUP*. The 11 most parsimonious trees support a monophyletic origin of the genera Antiporus Sharp, Nebrioporus Régimbart, Scarodytes Gozis, and Stictotarsus Zimmermann. Unambiguous synapomorphies supporting this clade are the presence of natatory setae on the femur, tibia and tarsus and the presence of a very elongate urogomphomere 1. It is postulated that these features evolved as swimming devices. The genus Oreodytes Seidlitz is postulated to represent the sister-taxon of Antiporus + Nebrioporus + Stictotarsus + Scarodytes and this clade is characterised by the absence of the maxillary cardo and insertion of the primary seta MX1 on the maxillary stipes.

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Ho, A. K., und C. L. Chik. „Inhibitors of Na(+)-H+ exchange block stimulus-provoked pineal melatonin synthesis“. American Journal of Physiology-Endocrinology and Metabolism 263, Nr. 3 (01.09.1992): E481—E488. http://dx.doi.org/10.1152/ajpendo.1992.263.3.e481.

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In rat pinealocytes, amiloride can modulate adrenergic-stimulated cyclic nucleotide accumulation. In this study, the effect of amiloride on melatonin production was characterized. Addition of 5-(N,N-hexamethylene)amiloride, a potent inhibitor of the Na(+)-H+ antiport, dose dependently inhibited norepinephrine- and isoproterenol-stimulated N-acetyltransferase (NAT) activity and melatonin production. Similar inhibition was also observed when pineal melatonin synthesis was stimulated directly with forskolin or dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP), suggesting that the site of inhibition is distal to cAMP accumulation. Similarities between the inhibitory potencies of amiloride derivatives on the Na(+)-H+ antiport and pineal melatonin synthesis indicate that the observed inhibition on pineal melatonin synthesis by amilorides may be secondary to their actions on the Na(+)-H+ antiport. Further studies also indicate that the inhibitory effect of amilorides was not secondary to its cytotoxic actions and that amilorides had no direct antagonistic action on NAT activity. Our findings, therefore, suggest that, in addition to their effects on cyclic nucleotide accumulation, the Na(+)-H+ antiport also plays an important role in the cAMP-mediated melatonin synthesis in the rat pineal gland.

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Lepier, A., M. Azuma, W. R. Harvey und H. Wieczorek. „K+/H+ antiport in the tobacco hornworm midgut: the K(+)-transporting component of the K+ pump.“ Journal of Experimental Biology 196, Nr. 1 (01.11.1994): 361–73. http://dx.doi.org/10.1242/jeb.196.1.361.

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The midgut of the tobacco hornworm secretes K+ across the apical plasma membrane of its goblet cells. This secondary K+ transport results from K+/H+ antiport energized by the proton-motive force generated by a primary, H(+)-transporting plasma membrane V-ATPase. Thus, the lepidopteran midgut constitutes a well-established example of the emerging concept that the proton-motive force is an alternative to the classical sodium-motive force for the energization of animal plasma membranes. K+/H+ antiport in the tobacco hornworm midgut is electrophoretic, exchanging 2H+ for 1K+. Under physiological conditions, it is energized by the voltage component of the proton-motive force. The strong coupling of electrophoretic K+/2H+ antiport with the electrogenic V-ATPase provides, in principle, the minimal device for the alkalization of the midgut lumen to pH values higher than 11. K+/H+ antiport is insensitive to bafilomycin A1, but is inhibited by amiloride or Concanavalin A. Lectin staining of blots after SDS-PAGE revealed several glycosylated polypeptides in the goblet cell apical membrane which are not part of the V-ATPase and thus are candidates for the antiporter protein. Current efforts are focused on the isolation of the K+/H+ antiporter.

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Michnowska, M., M. Smogorzewski und S. G. Massry. „Impaired Na(+)-H+ exchanger activity of hepatocytes in chronic renal failure.“ Journal of the American Society of Nephrology 8, Nr. 6 (Juni 1997): 929–34. http://dx.doi.org/10.1681/asn.v86929.

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Available data indicate that cation transport is impaired in many cells in chronic renal failure (CRF). The information on the activity of the Na(+)-H+ exchanger in CRF is variable, and both increased and reduced activity have been reported. The mechanisms through which CRF may exert an effect on the Na(+)-H+ transport are not known. Data exist indicating that PTH inhibits the Na(+)-H+ exchange in kidney and liver, and this action of hormone is most likely due to its ability to raise cytosolic calcium ([Ca2+]i). Therefore, it is possible that excess PTH in CRF may adversely affect the activity of the Na(+)-H+ antiport. This study examines the activity of Na(+)-H+ antiport, intracellular pH (pHi), and buffering capacity of hepatocytes obtained from rats after 6 wk of CRF, from CRF parathyroidectomized animals, and from CRF rats and normal rats treated with verapamil. The pHi and the buffering capacity of hepatocytes were not different in all groups of animals. The activity of the Na(+)-H+ antiport of hepatocytes from CRF animals was significantly (P < 0.01) lower than in hepatocytes from normal rats, CRF parathyroidectomized rats, CRF rats treated with verapamil, and normal rats treated with verapamil, and the values in the latter four groups of animals were not different. This impaired activity of Na(+)-H+ antiport in CRF was observed in all external concentrations of sodium (25, 50, 75, 100, 125, and 150 mM). Thus, CRF altered the kinetics of the transporter in that its Vmax decreased and its K(m) increased. The data show that: (1) CRF is associated with reduction in the activity of Na(+)-H+ antiport in hepatocytes; (2) this defect is due to the state of secondary hyperparathyroidism of CRF; and (3) excess PTH mediates its effect by elevating [Ca2+]i of hepatocytes because treatment of CRF animals with verapamil, which blocks the PTH-induced rise in [Ca2+]i of these cells, prevented the impairment in the activity of the Na(+)-H+ antiport.

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Grinstein, S., und H. Wieczorek. „Cation antiports of animal plasma membranes.“ Journal of Experimental Biology 196, Nr. 1 (01.11.1994): 307–18. http://dx.doi.org/10.1242/jeb.196.1.307.

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Mackovic-Basic, M., R. Fan und I. Kurtz. „Denervation inhibits early increase in Na(+)-H+ exchange after uninephrectomy but does not suppress hypertrophy“. American Journal of Physiology-Renal Physiology 263, Nr. 2 (01.08.1992): F328—F334. http://dx.doi.org/10.1152/ajprenal.1992.263.2.f328.

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Na(+)-H+ exchange in the rat proximal tubule luminal membrane increases approximately 30% within 15 min after the contralateral uninephrectomy. The present study was designed to test whether altered renal sympathetic nerve outflow to the remaining kidney is the underlying mechanism of increased antiport activity and whether suppression of Na(+)-H+ antiport activity by renal denervation inhibits renal hypertrophy in the remaining kidney after uninephrectomy. Sprague-Dawley rats were divided into four groups: 1) sham operated, 2) uninephrectomized, 3) uninephrectomized with prior denervation of the remaining kidney, and 4) contralateral renal denervation. Na(+)-H+ antiport activity (brush-border vesicles), Na(+)-K(+)-ATPase activity (basolateral vesicles), and kidney weight were measured days 1-7. On days 1 and 7, Na(+)-H+ antiport activity and Na(+)-K(+)-ATPase activities were significantly greater in uninephrectomized rats. Denervation of the remaining kidney before contralateral uninephrectomy prevented the stimulation of the antiporter and Na(+)-K(+)-ATPase activity, but failed to inhibit renal hypertrophy by day 7. In separate experiments, contralateral renal denervation alone without removal of the kidney stimulated the Na(+)-H+ antiporter and Na(+)-K(+)-ATPase activity. Kidney weight, however, remained unchanged. The results demonstrate a dissociation between the activation of the Na(+)-H+ antiporter and induction of renal hypertrophy in vivo.

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Hoffmann, G., Y. Ko, A. Sachinidis, B. O. Gobel, H. Vetter, D. Rosskopf, W. Siffert und R. Dusing. „Kinetics of Na+/H+ exchange in vascular smooth muscle cells from WKY and SHR: effects of phorbol ester“. American Journal of Physiology-Cell Physiology 268, Nr. 1 (01.01.1995): C14—C20. http://dx.doi.org/10.1152/ajpcell.1995.268.1.c14.

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The kinetic properties of Na+/H+ exchange were investigated in vascular smooth muscle cells (VSMC) in culture from normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Antiport activity was measured in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein-loaded cells after nigericin-induced cytosolic acidification. Studies were performed without (control) and with pretreatment of the cells with phorbol 12-myristate 13-acetate (PMA; 200 nM). Na+/H+ exchange markedly differed between the two strains with lower Hill coefficients [1.56 +/- 0.17 (SE) vs. 2.62 +/- 0.36] and higher maximal activity (Vmax) values (55.85 +/- 5.24 vs. 31.11 +/- 2.38 mmol H+.l-1.min-1) in SHR compared with WKY cell lines. PMA markedly altered the antiport kinetics in WKY VSMC with a decrease in the Hill coefficient (1.75 +/- 0.14) without affecting Vmax (31.88 +/- 1.55 mmol H+.l-1.min-1). In VSMC from SHR, PMA had no effect on the kinetic variables investigated. Thus two kinetic abnormalities are present with respect to Na+/H+ antiport activity in VSMC from SHR compared with WKY, i.e., increased Vmax and decreased Hill coefficient. The observation that PMA does not affect the kinetics of the Na+/H+ antiport in VSMC from SHR suggests a marked degree of antiporter prestimulation in this animal model of genetic hypertension.

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Ullmann, Roland, Roland Gross, Jörg Simon, Gottfried Unden und Achim Kröger. „Transport of C4-Dicarboxylates inWolinella succinogenes“. Journal of Bacteriology 182, Nr. 20 (15.10.2000): 5757–64. http://dx.doi.org/10.1128/jb.182.20.5757-5764.2000.

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ABSTRACT C4-dicarboxylate transport is a prerequisite for anaerobic respiration with fumarate in Wolinella succinogenes, since the substrate site of fumarate reductase is oriented towards the cytoplasmic side of the membrane. W. succinogenes was found to transport C4-dicarboxylates (fumarate, succinate, malate, and aspartate) across the cytoplasmic membrane by antiport and uniport mechanisms. The electrogenic uniport resulted in dicarboxylate accumulation driven by anaerobic respiration. The molar ratio of internal to external dicarboxylate concentration was up to 103. The dicarboxylate antiport was either electrogenic or electroneutral. The electroneutral antiport required the presence of internal Na+, whereas the electrogenic antiport also operated in the absence of Na+. In the absence of Na+, no electrochemical proton potential (Δp) was measured across the membrane of cells catalyzing fumarate respiration. This suggests that the proton potential generated by fumarate respiration is dissipated by the concomitant electrogenic dicarboxylate antiport. Three gene loci (dcuA,dcuB, and dctPQM) encoding putative C4-dicarboxylate transporters were identified on the genome of W. succinogenes. The predicted gene products ofdcuA and dcuB are similar to the Dcu transporters that are involved in the fumarate respiration ofEscherichia coli with external C4-dicarboxylates. The genes dctP, -Q, and -M probably encode a binding-protein-dependent secondary uptake transporter for dicarboxylates. A mutant (DcuA− DcuB−) ofW. succinogenes lacking the intact dcuA anddcuB genes grew by nitrate respiration with succinate as the carbon source but did not grow by fumarate respiration with fumarate, malate, or aspartate as substrates. The DcuA−, DcuB−, and DctQM− mutants grew by fumarate respiration as well as by nitrate respiration with succinate as the carbon source. Cells of the DcuA− DcuB−mutant performed fumarate respiration without generating a proton potential even in the presence of Na+. This explains why the DcuA− DcuB− mutant does not grow by fumarate respiration. Growth by fumarate respiration appears to depend on the function of the Na+-dependent, electroneutral dicarboxylate antiport which is catalyzed exclusively by the Dcu transporters. Dicarboxylate transport via the electrogenic uniport is probably catalyzed by the DctPQM transporter and by a fourth, unknown transporter that may also operate as an electrogenic antiporter.

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Baysal, K., D. W. Jung, K. K. Gunter, T. E. Gunter und G. P. Brierley. „Na(+)-dependent Ca2+ efflux mechanism of heart mitochondria is not a passive Ca2+/2Na+ exchanger“. American Journal of Physiology-Cell Physiology 266, Nr. 3 (01.03.1994): C800—C808. http://dx.doi.org/10.1152/ajpcell.1994.266.3.c800.

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Net Ca2+ flux across the inner membrane of respiring heart mitochondria was evaluated under conditions in which virtually all Ca2+ movement can be attributed to the Na+/Ca2+ antiport. If this antiport promotes a passive electroneutral exchange of Ca2+ for 2Na+, the Ca2+ gradient should be equal to the square of the Na+ gradient at equilibrium. Because the mitochondrial Na+/H+ antiport equilibrates the Na+ and H+ gradients, the Ca2+ gradient should also equal the square of the H+ gradient. In a series of > 20 determinations at different matrix [Ca2+], different delta pH, and varying membrane potential, it was found that Ca2+ is transported out of the mitochondrion against gradients from 15- to 100-fold greater than the value predicted for passive electroneutral exchange. It is concluded that the observed gradients are too large to be sustained by passive Ca2+/2Na+ exchange. The observed gradients are compatible with an electrogenic Ca2+/3Na+ exchange. Alternatively another source of energy is available to support these gradients.

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Niggli, Verena, und Erwin Sigel. „Anticipating antiport in P-type ATPases“. Trends in Biochemical Sciences 33, Nr. 4 (April 2008): 156–60. http://dx.doi.org/10.1016/j.tibs.2007.12.005.

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47

Radchenko, Martha V., Kimihiro Tanaka, Rungaroon Waditee, Sawako Oshimi, Yasutomo Matsuzaki, Masahiro Fukuhara, Hiroshi Kobayashi, Teruhiro Takabe und Tatsunosuke Nakamura. „Potassium/Proton Antiport System ofEscherichia coli“. Journal of Biological Chemistry 281, Nr. 29 (09.05.2006): 19822–29. http://dx.doi.org/10.1074/jbc.m600333200.

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48

Moore, Stephen J., Matthew G. Fisher, Masafumi Yano, Christine C. Tong und Philip A. Gale. „A synergistic approach to anion antiport“. Dalton Transactions 40, Nr. 45 (2011): 12017. http://dx.doi.org/10.1039/c1dt10213c.

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Csuhaj-Varjú, Erzsébet, Maurice Margenstern, György Vaszil und Sergey Verlan. „On small universal antiport P systems“. Theoretical Computer Science 372, Nr. 2-3 (März 2007): 152–64. http://dx.doi.org/10.1016/j.tcs.2006.11.023.

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50

Andrade, Susana L. A., und Oliver Einsle. „Nitrat/Nitrit-Antiport: eine schwierige Aufgabe“. Angewandte Chemie 125, Nr. 40 (09.08.2013): 10614–16. http://dx.doi.org/10.1002/ange.201305421.

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