Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:EXPT00514 (Amiloride)
 1,513 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transepithelial electrical characteristics of the isolated yolk sac membrane of normal in ovo or shell-less cultured chick embryos were investigated. In normal chicks the potential difference (blood side positive relative to yolk side) and short-circuit current of the membrane increased during development. Ouabain (10(-4) M) on the blood side (basolateral side, serosal side) significantly decreased potential difference and short-circuit current but was without effect on the yolk side (brush border side, mucosal side). Substitution of choline for Na+ in the bathing solutions abolished the potential difference and the short-circuit current; when Na+ replaced choline this effect was reversed. Amiloride added to both sides of the yolk sac membrane had no effect on potential difference or short-circuit current. Injection of aldosterone (50 micrograms) and T3 (10 microM) into yolk did not induce amiloride sensitivity. The short-circuit current was not altered by addition of either glucose or alanine to the bath. The short-circuit current of the yolk sac membrane of shell-less cultured embryos was significantly lower than that of normal controls. Addition of Ca2+ to the serosal bathing medium did not reverse the foregoing condition, but decreased the short-circuit current. It is concluded that the yolk sac short-circuit current is Na+ dependent and increases with developmental age in the chick embryo.
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PMID:Sodium-dependent short-circuit current across the yolk sac membrane during embryonic development in normal and shell-less cultured chicks. 143 Apr 19

Promastigotes from late-log phase cultures of Leishmania donovani were washed and resuspended in Hanks' Balanced Salt Solution without glucose or phenyl red but with 20 mM (N-[2-hydroxyethyl] piperazine-N'-[2-ethanesulfonic acid]) (HEPES) (HBSS-, 305 mOsm/kg). They were then added to a solution containing 86Rb such that the final osmolality and ionic composition was as desired. Samples were taken at known times and the amount of intracellular 86Rb was measured. Similarly, experiments were performed in which 86Rb was added to the cultures about 18 hr before collection, and the amount of 86Rb released from the washed cells was measured. Under iso-osmotic conditions only about 1.3% of the intracellular 86Rb was released in 900 sec. This increased about 4-fold if the osmolality was reduced from 305-153 mOsm/kg. This is much slower than the very rapid release of alanine in response to hypo-osmotic stress, indicating that alanine release is not via a non-specific pore. Reducing the temperature from 26 degrees C to 3-4 degrees C completely inhibits 86Rb release under iso-osmotic conditions and largely inhibits it under hypo-osmotic conditions. The rate of 86Rb release was not sensitive to K+ concentration and was not altered if chloride was replaced by sulfamate. Ouabain had no effect on either 86Rb uptake or release, but carbonylcyanide P-trifluoromethoxyphenylhydrazone (FCCP) reduced the rate of 86Rb release and, after about a 300 sec exposure, completely inhibited 86Rb uptake. Amiloride partially inhibited 86Rb release, but had no effect on uptake. A decrease in pH from 7.1-5.9 had little effect on 86Rb release under iso-osmotic conditions and slightly increased the rate of release under hypo-osmotic conditions, but it decreased the rate of uptake under both iso-osmotic and hypo-osmotic conditions. Cells taken from 3-day stationary phase cultures released 86Rb more slowly under iso-osmotic conditions than cells from late log phase cultures, but were more responsive to hypo-osmotic stress than were log phase cells. These data appear to rule out an [Na-K-Cl] transporter or a [K-Cl] cotransporter as the means of K+ release, but are consistent with the possibility that a K+/H+ exchanger is present. The possibility that other carrier systems may be present is also discussed.
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PMID:Effect of osmolality on 86Rb+ uptake and release by Leishmania donovani. 161 13

Amiloride, a commonly used inhibitor of Na+-H+ exchange, has been shown to exhibit a variety of nonspecific effects. Recently, the more potent amiloride analogs, 5-(N,N-dimethyl)amiloride hydrochloride (DMA) and 5-(N-ethyl-N-isopropyl)amiloride (EIA), have been used to control for the nonspecific effects of the parent compound. In the present study, we have explored the effects of these analogs on Na+/K+-transporting ATPase (Na+/K+-ATPase) and Na+-coupled alanine transport in primary rat hepatocyte cultures and rat liver plasma membranes, and we have compared the effects of these analogs with the effects of amiloride and ouabain. Amiloride, DMA, and EIA increased steady-state Na+ content and inhibited ouabain-sensitive 86Rb+ uptake in a reversible, concentration-dependent, ouabain-like manner, with estimated 50% inhibitory concentrations (IC50) of 3.0.10(-3) M, 5.2.10(-4) M, and 1.2.10(-4) M, respectively. Amiloride, DMA and EIA also inhibited ouabain-sensitive ATP hydrolysis in rat liver plasma membranes with similar potency (IC50 values of 2.2.10(-3) M, 2.2.10(-3) M, and 1.7.10(-4) M, respectively). In separate experiments, amiloride (5.10(-3) M), DMA (10(-3) M), and EIA (2.5.10(-4) M) decreased the uptake into hepatocytes of alanine by 20%, 61%, and 59%, respectively, and further studies with DMA (10(-3) M) demonstrated that this inhibition was largely due to a decrease in the Na+-dependent fraction of alanine uptake. These findings indicate that amiloride, DMA, and EIA inhibit hepatic Na+/K+-ATPase directly, reversibly, and with a relative rank order potency of EIA greater than DMA greater than amiloride. All three compounds also inhibit the hepatic uptake of alanine, and presumably could indirectly inhibit other Na+-coupled transport processes as well.
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PMID:Amiloride and amiloride analogs inhibit Na+/K+-transporting ATPase and Na+-coupled alanine transport in rat hepatocytes. 245 May 81

We examined the effect of amiloride on Na+-H+ exchange in rabbit renal cortical microvillus membrane vesicles. Amiloride inhibited both the uphill Na+ accumulation induced by imposition of a transmembrane Hin+ greater than Hout+ gradient and the uphill H+ efflux induced by imposition of a Naout+ greater than Nain+ gradient. The inhibitory effect of amiloride on Na+ influx was rapidly reversible and fully competitive (Ki 3.0 X 10(-5) M amiloride, KT 6.3 mM Na+). In addition, amiloride inhibited the efflux of Na+ from vesicles preloaded with Na+. However, the diuretic did not inhibit such other Na+-coupled transport processes as Na+-glucose ad Na+-alanine cotransport. These findings suggest that amiloride is a reversible, selective, competitive inhibitor for the Na+ site of the renal microvillus membrane Na+-H+ exchanger. Amiloride may, therefore, be useful as an experimental tool for investigating the role of Na+-H+ exchange in mediating proximal tubular acidification.
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PMID:Amiloride inhibition of the Na+-H+ exchanger in renal microvillus membrane vesicles. 731 61

The short term effect of heavy water (2H2O) in intracellular pH (pHi) and phosphatidylcholine (PtdCho) turnover have been studied by 31P NMR spectroscopy in the perfused mouse liver metabolizing alanine. Hepatic pHi decreased from 7.19 +/- 0.01 (n = 10) to 7.01 +/- 0.03 (n = 4) after the addition of 6 mM alanine to Krebs Ringer bicarbonate (KRB) perfusion medium. Replacement of 50% of the KRB water with 2H2O during alanine perfusion inhibited the intracellular acidification induced by alanine and caused i) a decrease in the hepatic content of PtdCho, and ii) increases in phosphocholine and glycerophosphocholine, respectively. Amiloride (1 mM) of 5-(N-ethyl-N-isopropyl)-amiloride (10 microM), two previously reported inhibitors of the Na+/H+ exchangers, mimicked the effects produced by 2H2O on pHi and PtdCho turnover. Replacement of 50% of the KRB water with 2H2O or the addition of 1mM amiloride to KRB only, did not modify pHi nor increase the levels of phosphocholine of glycerophosphocholine. Thus, the observed increases are the result of alanine perfusion in the presence of 2H2O or amiloride. These results suggest that 2H2O behaves similarly to previously reported inhibitors of Na+/H+ exchange, disclosing also a novel role for PtdCho metabolism in the regulation on hepatic pHi.
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PMID:Effects of heavy water on hepatic intracellular pH and phosphatidylcholine turnover. A 31P NMR study. 929 95

Human acid-sensing ion channel 1b (hASIC1b) is a H(+)-gated amiloride-sensitive cation channel. We have previously shown that glioma cells exhibit an amiloride-sensitive cation conductance. Amiloride and the ASIC1 blocker psalmotoxin-1 decrease the migration and proliferation of glioma cells. PKC also abolishes the amiloride-sensitive conductance of glioma cells and inhibits hASIC1b open probability in planar lipid bilayers. In addition, hASIC1b's COOH terminus has been shown to interact with protein interacting with C kinase (PICK)1, which targets PKC to the plasma membrane. Therefore, we tested the hypothesis that PKC regulation of hASIC1b at specific PKC consensus sites inhibits hASIC1b function. We mutated three consensus PKC phosphorylation sites (T26, S40, and S499) in hASIC1b to alanine, to prevent phosphorylation, and to glutamic acid or aspartic acid, to mimic phosphorylation. Our data suggest that S40 and S499 are critical sites mediating the modulation of hASIC1b by PKC. We expressed mutant hASIC1b constructs in Xenopus oocytes and measured acid-activated currents by two-electrode voltage clamp. T26A and T26E did not exhibit acid-activated currents. S40A was indistinguishable from wild type (WT), whereas S40E, S499A, and S499D currents were decreased. The PKC activators PMA and phorbol 12,13-dibutyrate inhibited WT hASIC1b and S499A, and PMA had no effect on S40A or on WT hASIC1b in oocytes pretreated with the PKC inhibitor chelerythrine. Chelerythrine inhibited WT hASIC1b and S40A but had no effect on S499A or S40A/S499A. PKC activators or the inhibitor did not affect the surface expression of WT hASIC1b. These data show that the two PKC consensus sites S40 and S499 differentially regulate hASIC1b and mediate the effects of PKC activation or PKC inhibition on hASIC1b. This will result in a deeper understanding of PKC regulation of this channel in glioma cells, information that may help in designing potentially beneficial therapies in their treatment.
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PMID:Two PKC consensus sites on human acid-sensing ion channel 1b differentially regulate its function. 1909 60

The aim of this study was to characterize the transport mechanisms of electrolytes and nutrients across the jejunum of nine healthy horses electrophysiologically. The stripped mucosa was mounted in Ussing chambers and tissue conductances (G(t)) and short circuit currents (I(sc)) were continuously monitored. After blocking the sodium and potassium channels with amiloride, tetraethylammonium chloride (TEA) and barium, chloride secretion was stimulated by carbachol and forskolin. Subsequently, chloride channels were inhibited by 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid, 5-nitro-2-(3-phenylpropylamino)benzoic acid, CFTR(inh)-172, N-(2-naphtalenyl)-(3.5-dibromo-2.4-dihydroxyphenyl)methylene glycine hydrazide (GlyH-101) and glibenclamide and their dose-response effect was investigated. The response to glucose, l-alanine and glycyl-l-glutamine was determined at two different mucosal pH values (pH 7.4 and 5.4 respectively). Mean basal I(sc) was -0.47 +/- 0.31 microEq/cm(2)h and mean G(t) was 22.17 +/- 1.78 mS/cm(2). Amiloride and TEA did not alter the baseline I(sc). Barium, carbachol and forskolin significantly increased I(sc). Irrespective of the dose, none of the chloride inhibitors changed I(sc). All nutrients induced a significant increase in I(sc) with the increase being significantly higher at pH 7.4 than at pH 5.4. In conclusion, there is evidence that chloride secretion in horses may be different from respective transport mechanisms in other species. The glucose absorption is suggestive of a sodium-dependent glucose cotransporter 1. However, a decrease in luminal pH did not stimulate current response to peptides as shown for other mammals.
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PMID:Electrophysiological characterization of electrolyte and nutrient transport across the small intestine in horses. 1964 3