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)

V79 Chinese hamster cells were used as a model for the characterization of the Co(II) uptake into mammalian cells as well as the mechanisms involved. Co(II) was taken up in a dose and time dependent manner. The uptake was exponential without saturation in the tested concentration range up to 400 microM CoCl2. Furthermore, there was a high intracellular cobalt accumulation at elevated extracellular Co(II) doses (up to 16 fold at 200 microM). The time course of Co(II) uptake showed a maximum after about 8-12 h with no further change after the longest tested incubation time (24 h). The uptake of Co(II) into V79 cells seems to be mediated by multiple mechanisms: active, energy consuming transport like ion pumps and endocytosis, since the Co(II) uptake was significantly reduced by ouabain (an inhibitor of the Na+/K+ATPase), N-ethylmaleinimide (an inhibitor of the Ca2+/Mg2+ATPase and the Na+/K+ATPase), chlorpromazine (a calmodulin antagonist and inhibitor of the Ca2+/Mg2+ ATPase) as well as by the endocytosis inhibitor chloroquine. Furthermore, the two agents iodoacetate and potassium cyanide, which produce ATP depletion, resulted in a diminution of the intracellular cobalt concentration. An uptake through anion channels could be excluded, since 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid was not inhibitory.
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PMID:Mechanisms of cobalt(II) uptake into V79 Chinese hamster cells. 128 1

Rat optic nerves were studied in a sucrose gap chamber in order to study the origin of a late afterhyperpolarization that follows repetitive activity. The results provide evidence for electrogenic pump (Na+/K(+)-ATPase) activity in central nervous system myelinated axons and demonstrate an effect on axonal excitability. Repetitive stimulation (25-200 Hz; 200-5000 ms) led to a prolonged, temperature-dependent post-train afterhyperpolarization with duration up to about 40 s. The post-train afterhyperpolarization was blocked by the Na+/K(+)-ATPase blockers strophanthidin and ouabain, and the substitution of Li+ for Na+ in the test solution, which also blocks Na+/K(+)-ATPase. The peak amplitude of the post-train afterhyperpolarization was minimally changed by the potassium-channel blocker tetraethylammonium (10 mM), and the Ca2(+)-channel blocker CoCl2 (4 mM). Hyperpolarizing constant current did not reverse the afterhyperpolarization. The amplitude of the hyperpolarization was increased in the presence of the potassium-channel blocker 4-aminopyridine (1 mM). In the presence of 4-amino-pyridine, the post-train hyperpolarization was much reduced by strophanthidin, except for a residual early component lasting several hundred milliseconds which was blocked by the potassium-channel blocker tetraethylammonium. This finding indicates that after exposure to 4-aminopyridine, repetitive stimulation leads to activation of a tetraethylammonium-sensitive K(+)-channel that contributes during the first several hundred milliseconds to the post-train afterhyperpolarization. The amplitude of the compound action potential elicited by a single submaximal stimulus during the post-train hyperpolarization was smaller than that of the control response. The decrement in amplitude was not present under identical stimulation conditions when the post-train hyperpolarization was blocked by strophanthidin, indicating that the hyperpolarization associated with repetitive stimulation reduced excitability.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Electrogenic pump (Na+/K(+)-ATPase) activity in rat optic nerve. 217 35

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

Studies of cation requirements in the recA-catalyzed proteolysis of lambda repressor and strand assimilation reactions have demonstrated that Co2+ significantly enhances both activities. In the presence of 4mM MgCl2, the optimal concentration of CoCl2 for proteolysis was 1mM. 2mM Co2+ increased the rate and extent of D-loop formation as measured by membrane filtration. Cobalt did not replace Mg2+ for the ssDNA-dependent ATPase activity of recA, and did not affect the rate of hydrolysis of ATP, measured over a wide range of DNA concentrations. Cobalt did prevent the Mg-dependent ssDNA renaturation catalyzed by recA protein. Membrane filter binding assays established that Co2+ increases the affinity of recA protein for ssDNA with ATP, dATP, or ATP gamma S as cofactors. The dissociation of recA protein from ssDNA-nucleoside triphosphate complex was much slower with CoCl2. This metal provides an excellent tool for dissecting the various activities inherent in recA protein.
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PMID:Cobalt: an effector of E. coli recA protein activity. 621 55

We recently reported a novel intracellular mechanism of renal Na-K-ATPase regulation by agents that increase cell cAMP, which involves protein kinase A-phospholipase A2 and is mediated by one or more arachidonic acid metabolites (Satoh, T., H. T. Cohen, and A. I. Katz. 1992. J. Clin. Invest. 89:1496). The present studies were, therefore, designed to assess the role of eicosanoids in the modulation of Na-K-ATPase activity in the rat cortical collecting duct. The effect of various cAMP agonists (dopamine, fenoldopam, vasopressin, forskolin, and dibutyryl cAMP), which inhibited the pump to a similar extent (approximately 50%), was independent of altered Na entry as it was elicited in the presence of amiloride or nystatin, or when NaCl was replaced with choline Cl. This effect was completely blocked by SKF 525A or ethoxyresorufin, two inhibitors of the cytochrome P450-dependent monooxygenase pathway, or by pretreating the animals with CoCl2, which depletes cytochrome P450. Equimolar concentrations (10(-7) M) of the cyclooxygenase inhibitors indomethacin or meclofenamate caused only a partial inhibition of the cAMP agonists' effect on the pump, whereas nordihydroguaiaretic acid or A 63162, two inhibitors of the lipoxygenase pathway, were without effect. Furthermore, two products of this pathway, leukotriene B4 and leukotriene D4, had no effect on Na-K-ATPase activity, and ICI 198615, a leukotriene receptor antagonist, did not alter pump inhibition by cAMP agonists. Several P450 monoxygenase arachidonic acid metabolites (5,6-epoxyeicosatrienoic acid; 11,12-epoxyeicosatrienoic acid; 11,12-dihydroxyeicosatrienoic acid; and 12(R)-hydroxyeicosatetraenoic acid) as well as PGE2 inhibited the Na:K pump in dose-dependent manner, but the effect of PGE2 was blocked when Na availability was altered, whereas that of 12(R)-HETE remained unchanged. We conclude that the cytochrome P450-monooxygenase pathway of the arachidonic acid cascade plays a major role in the modulation of Na:K pump activity by eicosanoids in the rat cortical collecting duct, and that products of the cyclooxygenase pathway may contribute to pump inhibition indirectly, by decreasing intracellular Na.
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PMID:Intracellular signaling in the regulation of renal Na-K-ATPase. II. Role of eicosanoids. 838 20

Acute systolic arterial hypertension provokes a rapid decrease in proximal tubule sodium reabsorption and diuresis associated with inhibition of renal cortex Na,K-ATPase activity and redistribution of apical membrane Na/H exchanger (NHE-3) to heavier density membranes containing markers of intermicrovillar cleft and endosomes. Because cytochrome P-450-dependent arachidonate metabolites participate in the regulation of renal sodium transport and BP, this study tested the hypothesis that these renal responses to acute hypertension would be prevented if cytochrome P-450 metabolism were inhibited by cobalt chloride (CoCl2). Four groups of rats (n = 4 to 5) were studied: (1) sham-operated; (2) 50 mg of CoCl2/kg subcutaneously for 2 d; (3) acute hypertension by constricting arteries for 5 min; and (4) acute hypertension after CoCl2 treatment as in group 3. Renal cortex was analyzed after sorbitol density gradient fractionation. CoCl2 treatment alone did not significantly affect the rate of urine output, endogenous lithium clearance (an inverse measure of proximal tubule sodium reabsorption), maximal activity of Na,K-ATPase, or subcellular distribution of NHE-3-containing membranes. In non-CoCl2-treated animals, acute hypertension provoked a three- to fourfold increase in urine output and endogenous lithium clearance, 33% inhibition of renal cortex Na,K-ATPase activity, and redistribution of NHE-3 out of the apical membrane peak. In CoCl2-treated animals, acute urine output and endogenous lithium clearance increased only twofold during acute hypertension, there was no inhibition of Na,K-ATPase activity, and there was no redistribution of NHE-3 immunoreactivity to higher density membranes. These findings demonstrate that CoCl2 treatment both attenuates the inhibition of proximal tubule sodium reabsorption and diuresis and abolishes Na,K-ATPase inhibition and NHE-3 redistribution during acute hypertension, evidence that these responses may be mediated by cytochrome P-450 arachidonate metabolites.
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PMID:The cytochrome P-450 inhibitor cobalt chloride prevents inhibition of renal Na,K-ATPase and redistribution of apical NHE-3 during acute hypertension. 955 54

The objective of these experiments was to determine the role of Ca2+ during oxytocin-stimulated prostaglandin (PG) F2 alpha release from bovine endometrial tissue in vitro. Uteri were collected from dairy cows on the day after spontaneous luteal regression. Caruncular endometrial explants were dissected and incubated in vitro to determine phospholipase C activity or PGF2 alpha release. A23,187 (a calcium ionophore) and maitotoxin (an activator of voltage-gated L-type calcium channels) stimulated release of PGF 2 alpha in a concentration-dependent manner (P < 0.05). Thapsigargin (induces accumulation of Ca2+ in the cytoplasm by inhibiting endoplasmic reticulum Ca2+/ATPase pumps) stimulated release of PGF2 alpha in a concentration-dependent manner as well (P < 0.13). Oxytocin (10(-6) M), AIF4- (a nonspecific activator of G-proteins; 10(-5) M), A23,187 (10(-5) M), and melittin (a stimulator of phospholipase A2; 10(-4) M) stimulated PGF2 alpha release when explants were incubated in Ca(2+)-free medium (P < 0.10); however, oxytocin, A23,187, or melittin were unable to stimulate PGF2 alpha release when explants were incubated in Ca(2+)-free medium containing the calcium chelator EGTA (P < 0.10). This treatment did not prevent oxytocin or AIF4- from stimulating phospholipase C activity (P < 0.08). CoCl2 (a nonspecific Ca2+ channel blocker) and methoxyverapamil (a specific voltage-gated L-type Ca2+ channel blocker) prevented oxytocin from stimulating PGF2 alpha release (P < 0.05). Our results suggest that both extracellular and intracellular Ca2+ may be required for oxytocin to stimulate PGF2 alpha secretion in bovine endometrial tissue.
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PMID:Cellular mechanisms by which oxytocin mediates uterine prostaglandin F2 alpha synthesis in bovine endometrium: role of calcium. 986 39

Isolated and cultured glomus cells, obtained from mouse carotid bodies, were superfused with Ham's F-12 equilibrated with air (mean PO2, 119 Torr; altitude 1350 m). [Ca2+]o was 3.0 mM. In one experimental series, dual cell penetrations with microelectrodes measured intracellular calcium ([Ca2+]i) and the resting potential (Em). In another series, [Ca2+]i was measured with Indo-1/AM, dissolved in DMSO. Normoxic cells had a mean Em of -42.4 mV and [Ca2+]i was about 80 nM (measured with both methods). The calculated calcium equilibrium potential (ECa) was 137+/-0.74 mV. Hypoxia, induced by Na2S2O4 1 mM, reduced pO2 to 10-14 Torr. This effect was accompanied by cell depolarization to -19.1 mV. Hypoxia increased [Ca2+]i to 231 nM when detected with Ca-sensitive microelectrodes, but only to 130.2 nM when measured with Indo-1/AM. Calcium increases were preceded by decreases in [Ca2+]i, which also were more pronounced with microelectrode measurements. CoCl2 1 mM blocked the hypoxic [Ca2+]i increase and exaggerated the decreases in [Ca2+]i. Correlations between DeltaEm and Delta[Ca2+]i during hypoxia were significant (p<0.05) in 19% of the cells. But, in 29% of them significance was at the p<0.1 level. In the rest (52%), there was no correlation between these parameters. Thus, voltage-gated calcium channels are rare in mouse glomus cells. Their activation by depolarization cannot explain the two to threefold increase in [Ca2+]i seen during hypoxia. More likely, [Ca2+]i increase may be due to hypoxic inactivation of a Ca-Mg ATPase transport system across the cell membrane. The blunting of hypoxic [Ca2+]i increase, seen in Indo-1/AM experiments, is probably due to its solvent (DMSO), which also depresses hypoxic cell depolarization.
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PMID:Effects of hypoxia induced by Na2S2O4 on intracellular calcium and resting potential of mouse glomus cells. 991 44

The concept that the location of an AAA-ATPase associated with the plant plasma membrane may be indicative of a functional relationship to growth or cell enlargement by analogy with roles in physical membrane displacements as proposed for AAA-ATPases associated with internal membranes was tested. A plant growth hormone-responsive and nucleoside triphosphate-dependent enlargement of inside-out vesicles of plasma membranes from soybeans was utilized in a completely cell-free system. The rate of enlargement was accelerated by the synthetic plant growth factor 2,4-dichlorophenoxyacetic acid (2,4-D) in a log dose-dependent manner and was increased approximately 2-fold with the addition of 1 microM 2,4-D plus 100 microM ATP compared to 100 microM ATP alone, 1 microM 2,4-D alone or no additions. The cell-free enlargement was inhibited by AAA-ATPase-specific antisera and by CoCl2, an inhibitor specific for AAA-ATPases. The responsible ATP site appears to be on the inside of the cell, since right side-out vesicles did not enlarge in response to either ATP, 2,4-D or the two in combination.
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PMID:Inside-out but not right side-out plasma membrane vesicles from soybean enlarge when treated with ATP + 2,4-D as determined by electron microscopy and light scattering: evidence for involvement of a plasma membrane AAA-ATPase. 1737 40