Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined cytoplasmic pH regulation in Schizosaccharomyces pombe and Saccharomyces cerevisiae using pH-sensitive fluorescent dyes. Of several different fluorescent compounds tested, carboxy-seminaphthorhodafluor-1 (C.SNARF-1) was the most effective. Leakage of C.SNARF-1 from S. pombe was much slower than leakage from C. cerevisiae. Using the pH-dependent fluorescence of C.SNARF-1 we showed that at an external pH of 7, mean resting internal pH was 7.0 for S. pombe and 6.6 for S. cerevisiae. We found that internal pH in S. pombe was maintained over a much narrower range in response to changes in external pH, especially at acidic pH. The addition of external glucose caused an intracellular alkalinization in both species, although the effect was much greater in S. cerevisiae than in S. pombe. The plasma membrane H(+)-ATPase inhibitor diethylstilbestrol reduced both the rate and extent of alkalinisation, with an IC50 of approximately 35 microM in both species. Amiloride also inhibited internal alkalinisation with IC50's of 745 microM for S. cerevisiae and 490 microM for S. pombe.
Mol Cell Biochem 1993 Jul 21
PMID:Intracellular pH in Schizosaccharomyces pombe--comparison with Saccharomyces cerevisiae. 823 84

Amiloride, an inhibitor of various sodium transporters, is toxic to Schizosaccharomyces pombe at low concentration in minimal but not in rich media. Amiloride-resistant mutants were isolated and shown to represent a new locus (car1 for changed amiloride resistance) on chromosome I. The car1 gene was cloned and sequenced. Sequence analysis revealed an open reading frame of 526 amino acids with a predicted molecular weight of 58,545 Da. It has 52% hydrophobic residues and belongs to the class of 12-transmembrane-domain transport proteins. Gene disruption of car1 results in increased amiloride resistance. car1 has sequence similarity to proteins from Candida associated with resistance to benomyl, methotrexate and cycloheximide. No single physiologically identifiable component of sodium transport appeared to be lost. We propose that car1 serves an uptake function, perhaps as a symport with an unknown substrate and this carrier may transport amiloride into the cell. Further, we suggest that amiloride toxicity at low concentrations is not due to its effect on sodium transport but, rather, depends on intracellular interference with an unknown biosynthetic pathway.
Mol Gen Genet 1993 Nov
PMID:The amiloride resistance gene, car1, of Schizosaccharomyces pombe. 824 83

The pulmonary epithelium's change from Cl(-)-dependent fluid secretion to Na(+)-dependent fluid absorption in late gestation appears to be important in the transition of the lung from a fluid-filled organ in utero to an air-filled organ after birth. This maturational process may be regulated in part by hormones. We examined the effects of hydrocortisone on ion transport across monolayer cultures of distal pulmonary epithelial cells isolated from the fetal rat. Hydrocortisone pretreatment enhanced terbutaline (10(-5) M) stimulation of short-circuit current (Isc) but only in monolayers derived from immature fetal cells (day 18 of gestation), stimulating basal Isc by 270% in control monolayers and by 329% in hydrocortisone-pretreated monolayers. Amiloride (10(-4) M) inhibited terbutaline-stimulated Isc by different amounts, depending on gestational age and pretreatment; Isc fell 40% in control monolayers derived from immature cells, 68% in hydrocortisone-pretreated monolayers from immature fetal cells, and approximately 70% in both control and hydrocortisone-pretreated monolayers from mature fetal cells (day 21 of gestation). The basal Isc in monolayers derived from immature cells was also variably inhibited by amiloride with Isc decreasing 26% in control monolayers and 57% in hydrocortisone-pretreated monolayers. The differential responses of terbutaline-stimulated Isc to benzamil, dimethylamiloride, and bumetanide suggested that Isc sensitivity to amiloride was dependent predominantly on Na+ channel activity regardless of gestational age or pretreatment. We conclude that hydrocortisone promotes the maturation of transepithelial Na+ transport in fetal rat lung epithelium by altering Na+ entry into the cell through Na+ channels. Hydrocortisone also enhances beta-adrenergic agonist stimulation of ion transport.
Am J Respir Cell Mol Biol 1993 Aug
PMID:Hydrocortisone promotes the maturation of Na(+)-dependent ion transport across the fetal pulmonary epithelium. 833 85

The roles of the Na+/H+ exchange system in the development and cessation of reperfusion induced ventricular arrhythmias were studied in the isolated perfused rat heart. The hearts were perfused in the working heart mode with modified Krebs Henseleit bicarbonate (KHB) buffer and whole heart ischemia was induced by a one-way ball valve with 330 beat/min pacing. Ischemia was continued for 15 min followed by 20 min of aerobic reperfusion (control). Amiloride (1.0 mM), an inhibitor of the Na+/H+ exchange system, was added to the KHB buffer only during reperfusion (group B) or only during ischemic periods (group C). Electrocardiographic and hemodynamic parameters were monitored throughout the perfusion. Coronary effluent was collected through pulmonary artery cannulation and PO2, PCO2, HCO3- and pH were measured by blood-gas analyzer. The incidence of reperfusion induced ventricular arrhythmias was 100%, 100% and 0% in control, group B and group C, respectively. The mean onset time of termination of reperfusion arrhythmias was significantly shorter in group B than in control. PCO2 increased from 39.0 +/- 0.9 to 89.3 +/- 6.0 mmHg at the end of ischemia in control and from 40.6 +/- 0.4 to 60.5 +/- 5.8 in group C, the difference between groups was statistically significant. HCO3- level decreased from 21.8 +/- 0.1 to 18.3 +/- 0.5 mmol/l in control, however, this decrease was significantly inhibited in group C (from 22.0 +/- 0.5 to 20.3 +/- 0.2). The increase in PCO2 and the decrease in HCO3- in group B were similar over time to those observed in control.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1993 Feb 17
PMID:Na+/H+ exchanger and reperfusion-induced ventricular arrhythmias in isolated perfused heart: possible role of amiloride. 838 97

Although many causal factors have been proposed for the ischemia-reperfusion injury, the exact mechanisms for interdependent derangements of mechanical, electrical and metabolic events remains unclear. For this purpose, the Langendorff-perfused rat hearts were subjected to regional brief ischemia followed by reperfusion to study the protective effects of amiloride, an inhibitor of Na(+)-H+ exchange. Amiloride (0.1 mM) attenuated the rise in tissue Na+ and Ca2+, both duration and incidence of arrhythmias (p < 0.05 vs. control), sarcolemmal injury (assessed by Na-K ATPase) and lipid peroxidation (assessed by malonedialdehyde formation) during reperfusion. Treatment of hearts with monensin, a sodium inophore, reversed the protective effects of amiloride. Reduction in transsarcolemmal Na+ and pH gradients during ischemia exhibited protective effects similar to those seen with amiloride. These results suggest that cardiac dysfunction, sarcolemmal injury and triggered arrhythmias during ischemia-reperfusion are due to the occurrence of intracellular Ca2+ overload caused by the activation of Na(+)-H+ exchange and Na(+)-Ca2+ exchange systems in the myocardium.
Mol Cell Biochem 1993 Apr 07
PMID:Effects of amiloride on the mechanical, electrical and biochemical aspects of ischemia-reperfusion injury. 838 83

There is evidence supporting the role of active transport of Na+ in the resolution of pulmonary edema, but the exact cellular mechanism(s) underlying this process remain unknown. This study demonstrated the presence of ion channels on adult rat alveolar type II cells that might be associated with this active transport of Na+. Patch-clamp techniques were used to characterize a nonselective cation channel in adult rat alveolar type II epithelial cells held in culture for 24 to 72 h. Single-channel currents were recorded from inside-out, cell-free membrane patches. The most common type of single channel had a linear slope conductance of 20.4 +/- 0.6 pS (n = 22) in symmetrical NaCl (150 mM) solutions. The channel was approximately equally permeable to Na+ and K+ ions (PK/PNa = 1.15) and was highly selective for cations (PCl/PNa < 0.05). Channel activity was Ca(2+)-dependent, and it required at least 10 microM Ca2+ on the cytosolic side of an inside-out patch to activate the channel. Amiloride (1 to 10 microM), a Na+ channel blocker in epithelial tissue, reduced the steady-state open probability of the channel 10-fold but had no significant effect on the magnitude of the single-channel conductance. Single channels with similar properties were not found in cultured rat alveolar macrophages. The possible role of this amiloride-sensitive, nonselective cation channel in Na+ transport and lung liquid clearance is discussed.
Am J Respir Cell Mol Biol 1993 Sep
PMID:Identification of nonselective cation channels in cultured adult rat alveolar type II cells. 839 61

Ecdysteroids play an important role in the larval moulting process of insects. 20-Hydroxyecdysone (20E) causes the induction of specific 'puffs' in polytene chromosomes of Drosophila melanogaster salivary gland cells. Although it is known that inorganic ions control pretranscriptional processes in the cell nucleus, the intracellular mechanisms of gene activation are still unclear. Therefore, we examined the effects of 20E on plasma membrane ion transport of Drosophila melanogaster salivary gland cells. Isolated glands of the third larval stage were superfused with a solution mimicking the haemolymph. The relative K+ conductance of the cell membrane (tK+) was measured with microelectrodes by performing ion substitution experiments. Under control conditions tK+ averaged to 0.16 + 0.02 (n = 15). Addition of 5 x 10(-6) M 20E increased tK+ within 2 min by 19.1 +/- 4.2% (n = 15). This rapid response to 20E was elicited only in the presence of calcium. Moreover, starting from a steady-state intracellular pH of 7.20-7.60, 20E induced a rise in cytoplasmic pH by 0.27 +/- 0.06 (n = 6) within minutes. Amiloride (10(-3) M), a blocker of plasma membrane Na+/H+ exchange, prevented the 20E-induced intracellular alkalinization. We conclude that 20E activates a calcium-sensitive plasma membrane Na+/H+ exchange leading to a rise of plasma membrane K+ conductance and intracellular alkalinization both being prerequisites for steroid hormone induced gene activation.
Mol Cell Endocrinol 1996 Jan 15
PMID:Rapid activation of calcium-sensitive Na+/H+ exchange induced by 20-hydroxyecdysone in salivary gland cells of Drosophila melanogaster. 882 67

The present study evaluates the activity of the Na/H antiport during cold ischemia and aims to determine its influence on cellular sodium. pH and volumes. Cellular parameters; volumes, sodium, pH and high energy phosphates, were measured by multinuclear NMR spectroscopy in rat hearts during 12 h of storage at 4 degrees C and reperfusion, along with functional parameters. Cell volumes were measured by 1H and 59Co NMR using the extracellular marker cobalticyanide, pH and energetics by 31P NMR and sodium compartmental distribution by 23Na NMR spectroscopy using the shift reagent Dy(TTHA)-3. Three storage solutions were applied: Krebs-Henseleit (containing 144 mM sodium, KH), a solution supplemented with 0.20 mM amiloride (KH-ami) and a solution containing 23 mM sodium and 242 mM mannitol (KH-man). Inhibition of the Na/H antiport with amiloride reduced the cellular sodium accumulation by 56%. The end-ischemic concentrations were 45 mM (KH-ami) and 77 mM (KH). Amiloride also reduced the extent of cell swelling by 53% from an end-ischemic volume of 3.56 ml/gdw (KH) to 2.97 ml/gdw (KH-ami), however cell swelling persisted in both groups at reperfusion (33% increase in cell water). The molar ratio of sodium and water cellular accumulation was constant: Na/H2O approximately 3.7 x 10(-3) throughout the whole storage period. Inhibition of the antiport was protective for the high energy phosphates during ischemia and reperfusion. In KH-ami the pH acidified after 6 h of storage to an end-ischemic value of 6.35 (pH = 6.50 in KH): this difference persisted after 60 min of reperfusion, pH = 6.98 in KH-ami and pH = 7.1 in KH. Storage in the low-sodium solution was disadvantageous for the high energy phosphates during ischemia and reperfusion with a recovery of pH to 6.92 when reperfused with KH. Hearts stored with amiloride or mannitol solution failed to resume contraction at reperfusion. It is concluded: (a) the antiport is active at 4 degrees C; (b) during ischemia it mediates sodium influx and contributes to cell swelling with minor effects on the cytosolic pH; (c) at reperfusion the antiport is active it participates in the extrusion of excess protons, but has a minor impact on sodium and water homeostasis; (d) inhibition of the antiport does not protect the cardiac muscle at low temperatures.
J Mol Cell Cardiol 1996 Mar
PMID:The relation between cellular sodium, pH and volumes and the activity of Na/H antiport during hypothermic ischemia: multinuclear NMR studies of rat hearts. 901 42

Activation of oocytes is caused by osmotic pressure change in some species. However, cryopreservation of oocytes occurs in the presence of osmotic pressure change induced by cryoprotectants. We investigated the effect of 5-(N,N,-dimethyl)-amiloride (NNDMA), a selective inhibitor of Na+/H+ exchange, on the cryopreservation and osmotic activation of mouse oocytes. The percentage (23.2%) of degenerate oocytes after cryopreservation in the presence of NNDMA was found to be lower than that (39.5%) of untreated oocytes. After thawing, the percentage (23.6%) of oocytes which could be fertilized following cryopreservation in the presence of NNDMA was significantly higher than that of untreated (18.0%) oocytes. These results suggest that amiloride increased the survival rate after thawing following cryopreservation. To investigate the effect of NNDMA on oocyte activation caused by the cryoprotectant, dimethyl sulphoxide (DMSO) was used to induce osmotic pressure change. NNDMA was found to inhibit cortical granule exocytosis, the second polar body emission and pronuclear formation which occurs upon activation due to osmotic pressure change. It also inhibited the increase in phosphorylation of many proteins including 33 and 45 kDa proteins, which occurs, during fertilization and chemical oocyte activation. In contrast, protein phosphorylation was not inhibited by W7, a calmodulin inhibitor. The actions of these inhibitors suggest that oocyte activation induced by osmotic pressure change involves a pathway mediated by Na+/H+ exchange which may be distinct from the Ca-calmodulin pathway. Amiloride may be a useful drug for increasing the rate of survival of cryopreserved oocytes.
Mol Hum Reprod 1996 Nov
PMID:Egg activation induced by osmotic pressure change and the effects of amiloride on the cryopreservation of mouse oocytes. 923 32

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.
Cell Mol Biol (Noisy-le-grand) 1997 Jul
PMID:Effects of heavy water on hepatic intracellular pH and phosphatidylcholine turnover. A 31P NMR study. 929 95


<< Previous 1 2 3 4 5 6 7 8 Next >>