Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hypokalaemia may be produced in man by intravenous adrenaline infusion, or as a result of pathological disturbances which have led to a high plasma adrenaline concentration. With isolated human leucocytes used as a cellular model, adrenaline at concentrations at and above 9 nmol/l increases the influx of rubidium (a model for potassium flux) into cells, with a simultaneous efflux of sodium. There is no effect on Na+,K+-ATPase activity in lysed leucocytes. Use of the adrenoceptor blockers timolol and atenolol shows that the demonstrated effect of adrenaline on coupled active transport of ions is mediated by beta 2-adrenoceptors.
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PMID:Adrenaline and ion flux in isolated human leucocytes. 257 59

We tested the hypothesis that a metabolic error may be the triggering mechanism which leads to blood-vessel hypertrophy and hypertension. Young spontaneously hypertensive rats (SHR) were fed a moderately high salt diet to exacerbate the purported metabolic error. Haematocrit values and rubidium transport were measured as evidence of renal ATP deficiency and blood-vessel adaptation. The renin system was inhibited in two groups of SHR by giving them enalapril to determine whether angiotensin II was involved in blood-vessel adaptation. Spontaneously hypertensive rats fed the moderately high salt diet had higher haematocrit values than normotensive rats fed the same diet or SHR fed Purina rat food, suggesting a renal ATP deficiency. Spontaneously hypertensive rats had higher Na+,K+-ATPase activity in thoracic aorta after 60 min incubation than a similar group given enalapril (P less than 0.001), suggesting blood-vessel adaptation. Possibly, angiotensin II within the vasa vasorum stimulates hypertrophy which, according to the Folkow hypothesis, leads to higher blood pressure, but may concomitantly increase the respiratory chain units which provide ATP for renal function and ion transport.
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PMID:Effect of a renin-system inhibitor on blood-vessel adaptation in spontaneously hypertensive rats. 282 Dec 7

This paper describes properties of a simple manual assay for Rb+ occlusion on renal (Na+ + K+)-ATPase. Rb+ occlusion is measured by applying the enzyme plus Rb+ (86Rb) mixture to a Dowex-50 cation exchange column at 0 degree C, and eluting the enzyme with occluded Rb+ using an ice-cold sucrose solution. The enzyme-Rb+ complex is quite stable at 0 degree C. This method is useful for measuring Rb+ occlusion under equilibrium binding conditions and slow rates of dissociation of the enzyme-Rb+ complex. The stoichiometry of Rb+ occluded per phosphorylation site is 2. Rb+ saturation curves are strictly hyperbolic, suggesting that the two Rb+ sites have very different affinities, one in the micromolar range and one in the tens of millimolar range. ATP shifts the Rb+ saturation curves to the right (control K0.5 100-200 microM; plus ATP, K0.5 0.8-1.4 mM, in a 100 mM Tris-HCl medium, pH 7.0) and reduces the maximal level occluded (control approx. 4 nmol/mg; plus ATP approx. 3 nmol/mg protein). Thus, as expected, ATP shifts the E(1)2Rb+-E2(2Rb+)occ equilibrium towards E1. Sodium ions at concentrations of up to 30 mM compete with the rubidium ions, KNa = 1.86 mM in the Tris-HCl medium. Na+ at higher concentrations (30-100 mM) has an added non-competitive antagonistic effect. At room temperature, Rb+ dissociates slowly from the enzyme, kobs = 0.08 s-1, in the presence of either Rb+ (20 mM) or Na, (100 mM). As expected, dissociation is greatly accelerated by ATP, the rate being to fast to be measured by this technique. (Na+ + K+)-ATPase proteolyzed selectively by chymotrypsin in a Na+ medium, occludes Rb+. For control and proteolyzed (Na+ + K+)-ATPase the Rb+ saturation curves are similar and the rates of dissociation of the enzyme-Rb+ complex are identical. The chymotryptic split appears to disrupt antagonistic interactions between cation and ATP binding domains, while the E1-E2 conformational transition of the unphosphorylated protein probably remains.
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PMID:Rb+ occlusion in renal (Na+ + K+)-ATPase characterized with a simple manual assay. 282 11

1,25-Dihydroxyvitamin D3 (calcitriol), or vitamin D3 itself, when added to cultures of 20-day-old embryonic chick small intestine, stimulated sodium (Na+) uptake from the mucosal surface. The calcitriol-mediated increase in Na+ uptake appeared to be related to increased tight-junctional or paracellular permeability. Support for this conclusion was, first, that the uptake of other ions, potassium (K+) and rubidium (Rb+), with tight-junctional permeabilities greater than Na+, was also stimulated by calcitriol, and second, perturbation of cellular Na+ and K+ fluxes by inhibition of Na+/K+-ATPase activity did not affect calcitriol-stimulated Na+, K+, or Rb+ transport. Calcitriol stimulation of Na+ fluxes across the brush border as an alternate possibility is unlikely for the following reason: the calcium ionophore A23187, while mimicking the stimulatory action of calcitriol on calcium (Ca2+) uptake, reduced epithelial Na+ uptake. It is therefore suggested that calcitriol, by virtue of its effect on Ca2+ transport, reduces rather than stimulates cellular Na+ uptake.
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PMID:Calcitriol-dependent, paracellular sodium transport in the embryonic chick intestine. 282 8

Sodium and potassium ion-activated adenosinetriphosphatase (EC number 3.6.1.3) activity, measured as the uptake of 86 rubidium (an analogue of potassium) was determined on peripheral lymphocytes isolated from 20 normotensive obese subjects and 20 normal weight subjects. No difference in the total uptake of 86Rb or in the Na, K-ATPase-dependent uptake was observed in either group. Furthermore, no correlation between the body mass index (BMI) and the Na,K-ATPase-dependent 86Rb uptake was observed. However the Na,K-ATPase mediated 86Rb uptake was always positively correlated with basal blood insulin levels and the insulin sensitivity index. It may be concluded that no lymphocyte dysfunction of Na,K-ATPase was present in our obese patients and that its activity is controlled by insulin in both normal-weight and obese subjects.
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PMID:Lymphocyte (Na,K) ATPase-dependent 86Rb+ uptake in human obesity. 285 84

1. Co2+ ions can replace Mg2+ ions as co-factors for the Na+-K+ pump purified from dog kidney outer medulla. The evidence comes from (a) measurement of ouabain-sensitive Na+,K+-ATPase activity, (b) measurement of ATP-dependent 22Na uptake catalysed by the Na+-K+ pump reconstituted into phospholipid vesicles, (c) measurements of phosphorylation of the Na+-K+ pump either in the presence of ATP and sodium ions or in the presence of inorganic phosphate, and (d) measurement of occlusion of rubidium ions through the route involving phosphorylation and dephosphorylation. 2. Purified Na+,K+-ATPase incubated in the presence of ATP, Na+ ions and [60Co]CoCl2, can carry occluded Co2+ ions through a cation-exchange resin. The enzyme fails to occlude the divalent cation (i) if ADP replaces ATP, (ii) if the enzyme is heat-inactivated, (iii) if the enzyme is inactivated by treatment with fluorescein isothiocyanate, (iv) if K+ replaces Na+ in the incubation medium, (v) if Na+ ions are omitted, and (vi) if Mg2+ ions are added in a sufficient concentration. 3. The amount of occluded Co2+ ions is unaffected by pre-treatment of the Na+,K+-ATPase with oligomycin, which stabilizes the phosphoenzyme in the E1P form. 4. The addition of K+ ions to Na+,K+-ATPase that has been phosphorylated in the presence of ATP, Na+ ions and [60Co]CoCl2 releases the occluded Co2+ ions from the enzyme. Under those conditions, K+ ions accelerate the hydrolysis of the phosphoenzyme, and become occluded in the resulting dephosphoenzyme. 5. The stoichiometry of Co2+ ion occlusion is about one occluded Co2+ ion per phosphorylation site. 6. These results support the hypothesis that, in the normal working of the Na+-K+ pump, Mg2+ ions are trapped in the phosphorylated forms of the enzyme, and are released by a K+-dependent dephosphorylation reaction.
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PMID:Occlusion of cobalt ions within the phosphorylated forms of the Na+-K+ pump isolated from dog kidney. 285 51

Vanadate is known to have an insulin-like action which stimulates sugar transport in some systems like adipocytes and muscle cells, but in other systems it inhibits sugar transport by decreasing the activity of (Na+ +K+)-ATPase. To evaluate whether these two opposing actions may influence sugar transport across the intestine, we studied the effects of acute and chronic vanadate administration on the uptake of glucose, galactose, and 3-O-methylglucose in isolated rat intestinal cells. The sugar uptake measurements were also coupled by determinations of rubidium-86 uptake as a measure of the activity of the Na-K pump. Both acute and chronic vanadate administration reduced rubidium uptake by the cells but the reduction did not uniformly influence the uptake of the three sugars in question which were stimulated by the acute exposure of the cells to vanadate. Glucose uptake was also stimulated by chronic vanadate administration, but the uptakes of galactose and 3-O-methylglucose were respectively unaffected or inhibited by chronic vanadate. The findings suggest that the effect of vanadate on sugar transport is dependent on the net difference between two actions of vanadate: (i) stimulation of a receptor site (possibly an insulin receptor site) in the intestinal cell membrane and (ii) inhibition of the Na-K pump. During acute vanadate exposure, the stimulation of the receptor site was very likely a dominant feature which overwhelms the inhibition of the pump. Chronic exposure to vanadate led, on the other hand, to only a limited degree of stimulation of the receptor site and the inhibition of the Na-K pump became evident in the uptake measurements of galactose and 3-O-methyl-glucose. Glucose uptake, however, was stimulated by chronic vanadate ingestion due, very likely, to an increase in the metabolism of this sugar which occurred only with prolonged exposure of the rat intestine to vanadate.
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PMID:Effect of acute and chronic vanadate administration on sugar transport in rat jejunum. 291 7

These studies were designed to investigate whether the antihypertensive effects of high potassium or low sodium diets are related to changes in vascular Na+,K+-adenosine triphosphatase (ATPase) activity. Vascular Na+,K+-ATPase was measured as ouabain-sensitive rubidium uptake in aorta incubated in buffer or plasma from spontaneously hypertensive rats (SHR) fed either a high potassium, a low sodium, or a normal diet for 2 weeks. The high potassium diet significantly increased Na+,K+-ATPase activity, whereas the low sodium diet significantly decreased activity. There was no evidence of a ouabainlike factor in plasma. The increased pump activity on the high potassium diet appeared to be due to an increase in maximum activity (Vmax) of the enzyme, rather than to an increased affinity for potassium. Potentially, an increase in Na+,K+-ATPase activity could contribute to the antihypertensive effect of potassium by hyperpolarizing the cell membrane. The decrease in vascular Na+,K+-ATPase activity on a low sodium diet probably is unrelated to its depressor effect, but it may be a homeostatic mechanism for maintaining sodium balance in the animal.
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PMID:Effects of high potassium or low sodium diet on vascular Na+,K+-ATPase activity and blood pressure in young spontaneously hypertensive rats. 295 81

Peribacteroid membranes can be isolated in essentially pure form from 20-day lupin root nodules by osmotic shock of the purified membrane enclosed bacteroids. The ATPase (EC 3.6.1.3) associated with this membrane has an acid pH optimum (5.25) and is specific for ATP (Mg-ATP Km = 0.16 mM). The enzyme activity requires magnesium or manganese ions, is slightly stimulated by the cations potassium and rubidium, and is inhibited by vanadate, diethylstilbestrol, N,N'-dicyclohexylcarbodiimide, fluoride, molybdate, and calcium. Molybdate and fluoride sensitivity do not in this case indicate the presence of significant nonspecific phosphatase activity. The ATPase is not inhibited by oligomycin, azide, or the soluble carbodiimide 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. In some respects the lupin peribacteroid membrane ATPase appears to differ from the plasma membrane ATPase of other plants.
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PMID:Characterization of the peribacteroid membrane ATPase of lupin root nodules. 296

The erythrocyte concentrations and the transmembrane fluxes of sodium and potassium were investigated in normal men and also in 20 normal women during the 2 stages of the menstrual cycle. 1/2 were taking oral contraceptives (OCS) and the other 1/2 were not. In women with a normal menstrual cycle, the erythrocyte sodium concentration (Naic) and the ouabain-insensitive total potassium efflux were lower in the luteal than in the follicular phase. Intracellular potassium concentration (Kic), ouabain-sensitive 86 rubidium-uptake, and the furosemide-sensitive Na+ and K+ afflux did not differ significantly between the 2 periods of the cycle. No cycle-related variation in Naic or Kic was observed in women using OCs. In these women, however, the ouabain-sensitive 86 rubidium-uptake was increased in the 2nd part of the menstrual cycle. When compared to men, the intra-erythrocyte sodium concentration was lower in women during the 2nd stage of the menstrual cycle. These 2 groups were similar for Na+, K+-ATPase pump activity estimated from the ouabain-sensitive 86 rubidium-uptake, and for the furosemide-sensitive sodium and potassium efflux. Women in the 1st stage of the menstrual cycle had intra-erythrocyte sodium concentration similar to men but their furosemide-sensitive sodium efflux was lower. No significant difference was obsesrved in the intra-erythrocyte potassium concentration and transmembrane fluxes of potassium in men and women in either stage of the menstrual cycle. The authors thus conclude that one should take into account sex-related variability when studying cationic fluxes and concentrations in red blood cells of men and women.
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PMID:Erythrocyte cationic transport systems in normal male and female volunteers. 298 91


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