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)

Vanadate(V), which has positive inotropic, natriuretic and vasoconstrictive effects, is taken up by cardiac cells and erythrocytes in large quantities. Most of the intracellular vanadium is shown to exist as protein-bound vanadyl(IV), however Vanadate (VO3) is a powerful inhibitor of the (Na+ rK+)-ATPase and the Ca++-ATPase, whereas it stimulates adenylate cyclase of cardiac tissue. Vanadyl (VO2+) has no or much less effects on these enzymes. Plasma membranes of cardiac tissue (cat, calf, human) as well as erythrocytes contain an enzyme that converts vanadate(V) to vanadyl(IV) in the presence of NADH but not NADPH. The optimal conditions for this NADH-vanadate-oxidoreductase are: pH 6.8, 1 mM, NADH, 1.5 mM Va3VO4. Mg++ inhibits the enzyme half-maximally at 3 mM, Ca++ stimulates at low and inhibits at high concentrations (half-maximally at 0.8 mM). The enzyme is supposed to be located at the inner side of the cell membrane. Vanadate has been proposed as an ideal regulator of active cation transport across the cell membrane. The finding of a HADH-vanadate-oxidoreductase converting vanadate into the rather inactive vanadyl further supports this hypotheses. The amount of vanadate at active sites of the target enzymes might be responsible for the known vanadate effects.
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PMID:Significance of NADH-vanadate-oxidoreductase of cardiac and erythrocyte cell membranes. 625 34

Looking for a supposed digitalis-like action of compounds of the trace element vanadium, we have investigated the influence of vanadate (Na3VO4) on beating and on active cation flux of [42K+] and [89Rb+] in cultured rat heart muscle cells: Na3VO4(10(-6)-10(-3)M) exerts a positive chronotropic effect and increases contraction velocity and beating automaticity of the cells. Vanadate-induced alteration of beating is paralleled by stimulated uptake of [42K+] and [86Rb+] up to 75%. This stimulation has to be attributed to increased activity of (Na++)-ATPase and cannot solely be explained by the enhanced beating frequency. In contrast to ouabain, vanadate raises intracellular potassium content up to 15% and prevents cell contractures of ouabain-intoxicated heart muscle cells. The experimental data speak against a possible digitalis-like action of vanadate in cultured rat heart muscle cells.
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PMID:Regulation of active cation flux by vanadate in beating rat heart muscle cells in culture. 625 35

The effect of ascorbic acid and noradrenaline on the inhibition of synaptosomal membrane ATPase by vanadate has been studied. Ascorbic acid (2 x 10(-3) M) and noradrenaline (10(-4) M) partly reversed the inhibition by vanadate (10(-6) M); however, when both were administered together the inhibition was completely eliminated. Using electron spin resonance (ESR) spectroscopy, we detected that ascorbic acid (10(-3) M) caused a 42% of reduction of vanadate (10(-4) M). Noradrenaline (10(-4) M) alone also reduced vanadate (10(-4) M) partially. When ascorbic acid and noradrenaline were present together all the vanadate was reduced to vanadyl. The concentration of ascorbic acid present in the brain under physiological conditions is identical to that found effective in our experiments. We suggest that ascorbic acid may protect the ATPase, at least in part, from inhibition by vanadate as a consequence of reducing vanadate to vanadyl. In those tissues where noradrenaline is also present a complete reduction of endogenous vanadium can be presumed.
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PMID:Reduction of Vanadate by ascorbic acid and noradrenaline in synaptosomes. 626 31

The renal actions of differing doses of sodium orthovanadate were studied in conscious and anesthetized female Wistar rats. In conscious rats, sodium orthovanadate was given by i.v. or i.p. injections or by mouth. The most pronounced renal effects were seen after a 5 mg/kg i.p. injection of sodium orthovanadate. Urine flow and sodium excretion increased approximately 400% and urine osmolality fell from 1108 to 549 mOsmol/kg . H2O. Higher doses of sodium orthovanadate (20, 30 and 50 mg/kg) injected i.p. did not cause diuresis and were toxic. In anesthetized rats undergoing a 0.9% NaCl diuresis, i.v. infusion of sodium orthovanadate at a dose of 5 mg/kg/hr significantly increased urine flow and the excretion of sodium, calcium, phosphorus, sulfur, magnesium and chlorine, whereas glomerular filtration rate was unaltered. In anesthetized rats undergoing a water diuresis, i.v. infusion of sodium orthovanadate (5 mg/kg/hr) markedly reduced free-water clearance, indicating that this compound inhibits tubular reabsorption of sodium and chloride in diluting nephron segments. Blood and renal tissue levels of vanadium, measured using emission spectrographic analysis, in rats infused with sodium orthovanadate were 4 times higher than the concentration of sodium orthovanadate (1--10 microM) needed to inhibit 50% of the Na-K-adenosine triphosphate activity of rat renal homogenates in vitro. These data suggest that sodium orthovanadate produces diuresis at least in part by inhibiting Na-K-adenosine triphosphatase and solute transport in the distal nephron, likely the ascending limb of the loop of Henle.
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PMID:Sodium orthovanadate diuresis in rats. 626 66

The effects of catecholamines (CA) and ethanol (EtOH), singly and in combination, on the kinetics of rat brain (Na+ + K+)-ATPase were studied. Addition of 0.05 M EtOH alone did not change Vmax or Km for K+, Na+, Mg2+ and ATP. Addition of 0.1 mM dopamine (DA) or noradrenaline (NA) alone stimulated the enzyme activity in presence of vanadium-containing ATP as substrate, but not with vanadium-free ATP except in the presence of high Mg2+ : ATP ratios. CA alone decreased the Km slightly for K+ and by about 50% for ATP, increased it for Mg2+ and did not change it for Na+. However, the combination of DA or NA + EtOH produced a marked inhibition which was competitive for K+, and uncompetitive or mixed for Mg2+, Na+ and ATP. The inhibitory effect of NA + EtOH was abolished in 20 mM K+. These findings suggest that NA sensitizes the enzyme to EtOH inhibition at physiological K+ concentrations, by conformational change away from the outwardly facing K+-binding E2P for to the inwardly facing Na+-binding E1P form.
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PMID:Interaction of catecholamines and ethanol on the kinetics of rat brain (Na+ + K+)-ATPase. 626 41

Vanadate, a potent naturally occurring Na+,K+-ATPase inhibitor thought to have a role in regulating Na+-K+ pump activity, was fed to uninephrectomized rats drinking tap water or a 1% solution of sodium chloride for as long as 56 weeks. Feeding was achieved by adding sodium orthovanadate to normal rat chow equivalent to 100 or 200 ppm vanadium by weight. In the rats drinking tap water, systolic pressure gradually increased over a period of several weeks and then was sustained in a dose-related manner for the duration of the treatment. The increased pressure was not associated with changes in water intake, urine output, or urinary sodium excretion but correlated positively with plasma vanadium levels ranging from 0.04 to 0.27 microgram/ml. Increased pressure was associated with increased heart-to-body-weight ratio but did not appear to occur in a small group of animals drinking the 1% solution of sodium chloride. These findings, considered in the light of others, indicate that vanadate deserves continued study in relation to hypertension.
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PMID:Effect of prolonged dietary administration of vanadate on blood pressure in the rat. 626 56

The (Na+ + K+)-ATPase of garfish olfactory nerve axon plasma membrane was purified about sixfold by treatment of the membrane with sodium dodecyl sulfate followed by sucrose density gradient centrifugation. The estimated molecular weights of the two major polypeptide components of the enzyme preparation on sodium dodecyl sulfate gels were 110,000 and 42,000 daltons, which were different from those of the corresponding peptides of rabbit kidney (Na+ + K+)-ATPase. No carbohydrate was detected in the 42,000-dalton component either by the periodic acid-Schiff reagent or by the more sensitive concanavalin A-peroxidase staining procedure. The molecular properties of the garfish (Na+ + K+)-ATPase, such as the Km for ATP, pH optimum, energies of activation, Na and K ion dependence and vanadium inhibition, were, however, similar to those of the kidney enzyme. The partially purified garfish (Na+ + K+)-ATPase was reconstituted into phospholipid vesicles by a freeze-thaw-sonication procedure. The reconstituted enzyme was found to catalyze a time and ATP dependent 22Na+ transport. The ratio of 22Na+ pumped to ATP hydrolyzed was about 1; under the same reconstitution and assay conditions, eel electroplax (Na+ + K+)-ATPase, however, gave a 22Na+ pumped to ATP hydrolyzed ratio of nearly 3.
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PMID:Partial purification and characterization of (Na+ + K+)-ATPase from garfish olfactory nerve axon plasma membrane. 627 69

133 samples of plasma taken from 9 normal control and 8 manic-depressive subjects were analysed for vanadium by atomic absorption spectrometry. Mean plasma vanadium concentrations were 0 . 15 microM in normal control, 0 . 34 microM in manic and 0 . 28 microM in depressed subjects, and 0 . 23 microM in manic-depressive subjects after recovery. The differences between normal subjects and manic and recovered subjects were statistically significant. Significant negative correlations were found between plasma vanadium concentration and the ratio of Na-K-Mg ATPase to Mg-ATPase in 2 manic-depressive subjects, but not in normal subjects. The results suggest that vanadium may be a cause of the variations in Na-K-Mg ATPase and sodium pump activity which are associated with manic-depressive illness.
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PMID:Plasma vanadium concentration in manic-depressive illness. 629 Oct 81

Vanadate is a potent inhibitor of Na-K-ATPase in vitro. It has been suggested that vanadium may function as a cellular regulator of Na-K-ATPase in vivo. To examine this speculation, we studied in rats the effect of high vanadate intake on 1) the tissue levels and distribution of vanadium, 2) basal activity of Na-K-ATPase in various tissues, and 3) the activity of Na-K-ATPase in various organs under conditions of massive chronic potassium loading known to stimulate Na-K-ATPase in the kidney and colon. Despite extremely high tissue levels of vanadium there was no demonstrable effect of the element on the basal activity of Na-K-ATPase. When subjected to chronic potassium loading, rats with high tissue vanadium concentrations underwent potassium adaptation that was associated with a rise in Na-K-ATPase activity in the renal cortex, renal medulla, and colonic mucosa. Further studies are needed to support or refute the thesis that vanadium might be an intracellular regulator of Na-K-ATPase in vivo.
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PMID:Vanadium, Na-K-ATPase, and potassium adaptation in the rat. 629 10

The influence of vanadium in the nominally +5 (NH4VO3; referred to as V5+), +4 (C10H14O5V and VOSO4; V4+) and +3 oxidation states (VCl3; V3+) on cardiac force of contraction, adenylate cyclase and (Na+ + K+)-ATPase activity was investigated in order to determine which form of vanadium mediates the cardiac effects. V5+, V4+ and V3+ (300 microM each) increased the force of contraction of isolated electrically driven cat papillary muscles by about 100%. In the presence of the reducing agent ascorbic acid (5 mM) none of the three compounds led to any distinct increase in force of contraction. On the particulate adenylate cyclase preparation from feline right ventricles only V5+ stimulated the enzyme activity by about 100%, whereas V4+ and V3+ were ineffective. In the presence of 5 mM ascorbic acid all three compounds were ineffective. In contrast, in the presence of the oxidizing agent diamide (azodicarboxylic acid-bis-dimethylamide; 1 mM) all three compounds became stimulatory. On the isolated (Na+ + K+)-ATPase V5+ (500 microM) alone reduced the basal activity by about 95%. In the presence of ascorbic acid the inhibitory effect of V5+ was greatly diminished. Similar results were obtained with V4+, V3+ (100 microM) alone inhibited (Na+ + K+)-ATPase activity only by about 40%. In the presence of ascorbic acid V3+ was ineffective. From the results it is concluded that positive inotropism, stimulation of adenylate cyclase and inhibition of (Na+ + K+)-ATPase by vanadium compounds likewise result from an action of vanadium in the +5 oxidation state.
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PMID:Effect of vanadium in the +5, +4 and +3 oxidation states on cardiac force of contraction, adenylate cyclase and (Na+ + K+)-ATPase activity. 629 2


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