Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The submaxillary duct epithelium, which actively transports Na+ (rabbit) and, in addition, K+ and H+/HCO-/3 (rat), was used as a model epithelium to compare the effects of ouabain and amiloride on transport parameters. 1. Ouabain was only effective from the interstitial side, amiloride, however, only from the luminal side. Amiloride induced effects on transport of the ions were seen within less than 1 s, ouabain effects, however, only after minutes. 2. Ouabain inhibited in a parallel fashion the Na+ transport potential and the Na+-K+-ATPase activity. It had no effect on the Mg2+-ATPase and the HCO-/3-ATPase. 3. Amiloride also inhibited the Na+ transport potential and the Na+-K+-ATPase; however, the Na+ transport potential was significantly more sensitive to amiloride than the Na+-K+-ATPase. 4. Amiloride inhibited in a similar fashion the Na+-K+-ATPase, the Mg2+-ATPase and the HCO-/3-ATPase, but did not influence active HCO-/3 secretion. 5. It is concluded that the amiloride induced effects on the membrane ATPases are non-specific.
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PMID:Non-specific inhibition of membrane-ATPase by amiloride: a comparative in vivo and in vitro study with ouabain. 18 83

Ouabain inhibited 86RbCl uptake by 80% in rabbit gastric superficial epithelial cells (SEC), revealing the presence of a functional Na+,K+-ATPase [(Na+ + K+)-transporting ATPase] pump. Intact SEC were used to study the ouabain-sensitive Na+,K+-ATPase and K+-pNPPase (K+-stimulated p-nitrophenyl phosphatase) activities before and after lysis. Intact SEC showed no Na+,K+-ATPase and insignificant Mg2+-ATPase activity. However, appreciable K+-pNPPase activity sensitive to ouabain inhibition was demonstrated by localizing its activity to the cell-surface exterior. The lysed SEC, on the other hand, demonstrated both ouabain-sensitive Na+,K+-ATPase and K+-pNPPase activities. Thus the ATP-hydrolytic site of Na+,K+-ATPase faces exclusively the cytosol, whereas the associated K+-pNPPase is distributed equally across the plasma membrane. The study suggests that the cell-exterior-located K+-pNPPase can be used as a convenient and reliable 'in situ' marker for the functional Na+,K+-ATPase system of various isolated cells under noninvasive conditions.
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PMID:Half of the (Na+ + K+)-transporting-ATPase-associated K+-stimulated p-nitrophenyl phosphatase activity of gastric epithelial cells is exposed to the surface exterior. 245 13

Ouabain-sensitive (Na+ + K+)-ATPase activity in the rat myometrial microsome fraction could only be determined following detergent treatment. The (Na+ + K+)-ATPase activity manifested by detergent treatment proved very stable even to high concentrations of NaN3, in contrast Mg+-ATPase activity was reduced to about 30 percent of the control. The major part of the Mg2+-ATPase in the myometrial membrane preparation was found to be identical with the NaN3-sensitive ATP diphosphohydrolase capable of ATP and ADP hydrolysis. This monovalent-cation-insensitive ATP hydrolysis could be extensively reduced by DMSO. Furthermore DMSO prevented the inactivation of the (Na+ + K+)-ATPase activity. 10-100 microM Ca2+ inhibited the (Na+ + K+)-ATPase activity obtained in the presence of SDS by 15-50 percent. The Ca2+ sensitivity of the enzyme was considerably decreased if the proteins solubilized by the detergent had been separated from the membrane fragments by ultracentrifugation. The inhibitory effect could be regained by combining the supernatant with the pellet. Ca2+ sensitivity of the (Na+ + K+)-ATPase activity was preserved even after removal of the solubilized proteins provided that DMSO had been applied. It appears that a factor in the plasma membrane solubilized by SDS may be responsible for the loss of Ca2+ sensitivity of the (Na+ + K+)-ATPase activity, the solubilization of which can be prevented by DMSO.
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PMID:Myometrial (Na+ + K+)-activated ATPase and its Ca2+ sensitivity. 299 86

1. Branchial Na+K+-ATPase specific activity is some 20% greater in hyposaline adapted Opsanus beta than in SW specimens. 2. Ouabain insensitive ATPase (Mg2+-ATPase) specific activities were similar, while whole body activity differences in low salinity and SW adapted fish could be accounted for by the 30% difference in extractable gill protein. 3. NH+4 ion was 15% more effective at dephosphorylation of the microsomal Na-dependent phosphoenzyme than either Rb+ or K+, and revealed a maximal ATPase affinity (Km = 0.2 mM) within the physiological range of blood [K+]. 4. Similar properties as pH optima, ATP and Mg2+ Km's, ouabain sensitivity, percent recoveries and subcell distribution indicated that the NH+4-stimulation acts through the Na+ K+-ATPase carrier enzyme and may be responsible for the Na+/NH+4 exchange in Opsanus beta.
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PMID:A carrier enzyme basis for ammonium excretion in teleost gill. NH+4-stimulated Na-dependent ATPase activity in Opsanus beta. 613 37

Isolated spontaneously beating rat hearts were perfused in the Langendorff mode and divided into four groups, i.e., control (aerobic), hypoxic (95% N2-5% CO2), ischemic, and ischemic reperfused. After a total of 90 min of perfusion, the sarcolemma was isolated and enzymatically characterized. Ouabain-sensitive Na+-K+-ATPase was inhibited in all three experimental groups, whereas K+-stimulated phosphatase activity was decreased only in the ischemic and reperfused groups compared with control. 5'-Nucleotidase activity was inhibited (P less than 0.05) only in the ischemic group. Mg2+-ATPase activity was not different from control. Passive Ca2+ uptake and Ca2+ efflux were not significantly altered by any of the interventions. Na+-Ca2+ exchange rate, but not capacity, was decreased (by 32-42%) in the ischemic group but this was partially reversed on reperfusion. These results suggest that changes secondary to lack of flow rather than O2 play a major role in the etiology of ischemic damage to the membrane and that a 15-min period of reperfusion after 60 min of ischemia does not exacerbate this damage.
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PMID:Sarcolemmal enzymes and Na+ -Ca2+ exchange in hypoxic, ischemic, and reperfused rat hearts. 614 98

In vitro sensitivity of rat brain and liver ATPases to pyrethroid insecticides, belonging to three categories based on the structural configuration, was studied. Rat brain and liver P2 fractions were prepared by the conventional centrifugation method, and rat brain synaptosomes were prepared by Ficoll-sucrose gradient centrifugation method. Na+, K+-ATPase and oligomycin-sensitive and -insensitive Mg2+- ATPases were determined in brain P2 fraction, whereas in liver P2 fraction only oligomycin-sensitive and -insensitive Mg2+-ATPase activities were determined. [3H]Ouabain binding studies were carried with rat brain synaptosomes. Most of the pyrethroid compounds tested inhibited brain and liver oligomycin-sensitive Mg2+-ATPases at micromolar concentrations. Type II compounds were more effective as compared to Type I compounds. Oligomycin-insensitive Mg2+-ATPase was not affected by any of the compounds tested except deltamethrin, which showed significant effect on liver enzyme. Na+, K+-ATPase of brain was less sensitive to these pyrethroids as compared to oligomycin-sensitive Mg2+-ATPase. [3H]Ouabain binding to rat brain synaptosomes was not affected significantly by these pyrethroid insecticides. These results suggest that inhibition of oligomycin-sensitive Mg2+-ATPase may be involved in the toxicity of pyrethroid compounds.
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PMID:In vitro effects of pyrethroids on rat brain and liver ATPase activities. 623 40

Membrane-bound enzyme activities and cardiac glycoside binding were determined in red blood cell membrane preparations from patients with myotonic dystrophy and in age matched controls. Na+-K+-activated ATPase activity was significantly increased in myotonic patients. [3H]Ouabain binding to erythrocyte membranes was also significantly increased in myotonic dystrophy patients. The Mg2+-ATPase (ouabain-insensitive) was, however, unchanged. The K+-stimulated paranitrophenyl phosphatase (KPNPPase) activity was markedly enhanced in myotonic patients as compared to controls. The kinetic analysis showed a marked change in Vmax of Na+-K+ ATPase with respect to the activation by Na+, K+ and ATP. However, the Km values were the same in control as well as in myotonic groups. The increased erythrocyte membrane Na+-K+-ATPase activity, KPNPPase and [3H]ouabain binding in myotonic patients supports the hypothesis that generalized membrane abnormality may be involved in pathogenesis of the human myotonic dystrophy.
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PMID:Erythrocyte membrane abnormalities in human myotonic dystrophy. 624 57

The effects of ouabain and furosemide on renin secretion, renal function, and renal Na+-K+-ATPase were investigated in anesthetized dogs. Furosemide (2 mg/kg) induced significant diuresis, natriuresis, an increase in renal blood flow (RBF), and a fivefold increase in renin secretory rate (RSR), but no changes in glomerular filtration rate (GFR). Infusion of ouabain (1 microgram . kg-1 . min-1) into one renal artery during furosemide diuresis increased fractional sodium excretion from 22 +/- 2 to 30 +/- 3% from the ipsilateral kidney but did not change urine flow, RBF, or GFR, whereas RSR fell to control values (698 +/- 203 to 137 +/- 43). When ouabain preceded furosemide, the rise in RBF and RSR induced by furosemide was abolished but sodium excretion increased. Ouabain infused in vivo inhibited Na+-K+-ATPase in microsomal fractions from cortex (34%) and medulla (27%) as compared with control. Neither saline nor furosemide exerted any effect on Na+-K+-ATPase. Moreover, the effect of ouabain alone on Na+-K+-ATPase was not different from that of ouabain plus furosemide. No changes in Mg2+-ATPase were detected in any of the experiments. These results indicate that inhibition of renal Na+-K+-ATPase abolishes furosemide-induced renin secretion despite potentiation of the natriuretic effect of the diuretic. It is apparent that the level of activity of Na+-K+-ATPase is of prime importance for renin secretion. In addition, ouabain may act directly on the juxtaglomerular cells to inhibit renin secretion.
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PMID:Renal Na+-K+-ATPase in renin release. 629 14