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)

In March, sexually immature sea trout presmolts (Salmo trutta trutta) were injected every second day with saline, 2 micrograms 17 beta-estradiol (E2)/g, 2 micrograms ovine growth hormone (GH) + 6 micrograms cortisol (F)/g, or all three hormones (E2-GH-F) simultaneously. A SW-challenge test was performed after six injections. At the time of SW-transfer, high total plasma calcium levels in E2- and E2-GH-F-treated fish indicated activated vitellogenesis in these groups. All control, GH-F, and E2-GH-F-treated fish survived SW-transfer, whereas 43% of the E2-treated fish died after transfer. On Day 2 after transfer, there were marked differences among groups in their osmoregulatory response. Changes in ion-osmotic parameters (plasma Na+, Cl-, Mg2+, and total calcium and muscle water) indicated the following degree of osmotic stress: E2 greater than control greater than E2-GH-F greater than GH-F, which was inversely correlated with pretransfer gill Na+/K(+)-ATPase activity: GH-F greater than E2-GH-F greater than control greater than E2. On Day 7 after transfer there were no major differences among the groups with regard to plasma ions and muscle water content. The detrimental influence of elevated plasma E2 levels on hypo-osmo-regulatory physiology may indicate an important role of E2 during development.
Gen Comp Endocrinol 1991 Aug
PMID:Opposite effects of 17 beta-estradiol and combined growth hormone-cortisol treatment on hypo-osmoregulatory performance in sea trout presmolts, Salmo trutta. 165 56

Effects of prolactin on morphology and numbers of chloride cells in the opercular membrane of seawater-adapted tilapia (Oreochromis mossambicus) have been examined. Following five daily injections of ovine prolactin at a dose of 10 micrograms.g body wt-1, blood samples were taken and opercular membranes were removed and stained with a fluorescent mitochondrial dye (dimethylaminostyrylethylpyridiniumiodine), a fluorescent derivative of ouabain (anthroylouabain), and a histological stain specific for the extensive tubular system of chloride cells (zinc-osmium-iodine). Mean plasma osmolarity and sodium increased 23-24% following prolactin injection. An increase in the relative frequency of chloride cells between 20 and 180 microns2 in cross-sectional area and a decrease in the relative frequency of chloride cells greater than 180 microns2 were observed following prolactin injections. Average cell size decreased 46-70% and cell height decreased 26-38% following prolactin injections. There was no significant change in cell density. Anthroylouabain staining was observed in both prolactin- and saline-injected fish, and no significant effect on Na+,K(+)-adenosinetriphosphatase activity was seen in either opercular membrane or gill tissue. The results demonstrate an effect of prolactin on chloride cell size and provide a morphological correlate for decreased secretory activity of chloride cells following prolactin injections.
Gen Comp Endocrinol 1991 Aug
PMID:Effects of prolactin on chloride cells in opercular membrane of seawater-adapted tilapia. 165 57

The intracellular Ca2+ concentration of nearly all cells is kept at submicromolar levels. The magnitudes of transmembrane Ca2+ movement that maintain this steady state in the human red blood cell have long been debated. Although there is agreement that the physiologic extrusion of Ca2+ by the well-characterized Ca2+. ATPase amounts to 45 mumol/liter cells per h (1982. Nature (Lond.). 298:478-481), the reported passive entry rates in physiological saline (2-20 mumol/liter cells per h) are all substantially lower. This discrepancy could be due to incomplete inhibition of the pump in the previous measurements of Ca2+ entry. We therefore examined both rate and mechanism of entry after completely inactivating the pump. This required pretreatment with iodoacetamide (to lower the intracellular ATP concentration) and vanadate (to inhibit any residual Ca2+ pump activity). The rate of Ca2+ entry (53 mumol/liter cells per h) was now found to be comparable to the accepted extrusion rate. Entry closely obeyed Michaelis-Menten kinetics (Vmax = 321 +/- 17 nmol Ca/g dry wt per h, Km = 1.26 +/- 0.13 mM), was competitively inhibited by external Sr2+ (Ki = 10.8 +/- 1.2 mM), and was accelerated by intracellular Ca2+. 45Ca2+ efflux from these pump-inactivated cells was also accelerated by either external Ca2+ or Sr2+. These accelerating effects of divalent cations on the opposite (trans) face of the membrane rule out a simple channel. Substrate-gated channels are also ruled out: cells equilibrated with 45Ca2+ lost the isotope when unlabeled Ca2+ or Sr2+ was added externally. Thus, passive Ca2+ movements occur predominantly by a reversible carrier-mediated mechanism for which Sr2+ is an alternate substrate. The carrier's intrinsic affinity constants for Ca2+ and Sr2+, 1.46 and 0.37 mM-1, respectively, indicate that Ca2+ is the preferred substrate.
J Gen Physiol 1991 Aug
PMID:Physiologic rate of carrier-mediated Ca2+ entry matches active extrusion in human erythrocytes. 165 94

1. The effects of bretylium on myocardial Mg(2+)-dependent, Na(+)-K(+)-ATPase (EC 3.6.1.3) activity were compared with those of ouabain in guinea-pig heart preparations. 2. Both ouabain and bretylium inhibited microsomal Na(+)-K(+)-ATPase activity in a concentration-dependent fashion in the range of 0.01-100 and 1.0-4000 microM, respectively. The IC50 values were 1.93 +/- 0.27 microM for ouabain and 2.45 +/- 0.17 mM for bretylium. 3. In another set of experiments, the effects of bretylium on the enzyme activity were tested in combination with 2.5 or 5.0 microM ouabain. 4. The combined effects of the two drugs resulted in a net reduction in the total inhibitory activities of the individual drugs, which became more marked the higher the bretylium concentration. This trend seems to suggest a competitive mode of interaction of the two drugs in their inhibitory actions on Na(+)-K(+)-ATPase activity. 5. The results demonstrate therefore that bretylium is a potent inhibitor of ouabain-inhibited ATP hydrolysis by myocardial Na(+)-K(+)-ATPase. These actions may be pertinent with regard to some of its cardiac actions.
Gen Pharmacol 1991
PMID:Interaction of bretylium tosylate with guinea-pig myocardial Na(+)-K(+)-ATPase. 166 73

The effect of extracellular pH (pHo) on the duration of calcium-dependent chloride currents (ICl(Ca] was studied in voltage clamped AtT-20 pituitary cells. ICl(Ca) was activated by Ca2+ influx through plasma membrane Ca2+ channels, which were opened by step depolarization to voltages between -20 and +60 mV. Increasing pHo from 7.3 to 8.0 reversibly prolonged ICl(Ca) tail currents in perforated patch recordings from cells bathed in both Na(+)-containing and Na(+)-free solutions. This prolongation was prevented in standard whole cell recordings when the pipette solution contained 0.5 mM EGTA. The effects of raised pHo were not due to alteration of intracellular pH, since tail current prolongation still occurred when intracellular pH was buffered at 7.3 with 80 mM HEPES. The prolongation of ICl(Ca) at pHo 8 could not be accounted for by a direct action on Ca2+ channels, since tail currents were prolonged when pHo was changed rapidly during the tail current, after all Ca2+ channels were closed. The effects of increasing pHo on ICl(Ca) also could not be explained by a direct action on Cl- channels, since changing to pHo 8 did not prolong Cl- tail currents when intracellular Ca2+ concentration [( Ca2+]i) was fixed by EGTA in whole cell recordings. Raising pHo did, however, prolong depolarization-evoked [Ca2+]i transients, measured directly with the Ca2+ indicator dye, fura-2. Taken together, these data demonstrate the presence of a Na(+)-independent, pHo-sensitive mechanism for reduction of [Ca2+]i after influx through Ca2+ channels. This mechanism is associated with the plasma membrane, and is active on a time scale that is relevant to the duration of single action potentials in these cells. We suggest that this mechanism is the plasma membrane Ca2+ ATPase.
J Gen Physiol 1991 Nov
PMID:A [Na+]o-independent, pHo-dependent mechanism for reduction of intracellular [Ca2+] after influx through Ca2+ channels in mouse pituitary cells. 166 85

The ability of cortisol to increase gill Na+,K(+)-ATPase activity was examined in several salmonid species during development. Coho salmon (Oncorhynchus kisutch) parr were unresponsive to cortisol in vitro (10 micrograms/ml for 2 days) in November. Responsiveness was significant from January to March, peaking in January just prior to seasonal increases in gill Na+,K(+)-ATPase activity. Gill tissue became unresponsive to in vitro cortisol in April when in vivo gill Na+,K(+)-ATPase activity peaked. The ability of cortisol to stimulate gill, Na+,K(+)-ATPase activity in postemergent fry (2-3 months after hatching) was examined in chum (O. keta), chinook (O. tschawytscha), coho, and Atlantic salmon (Salmo salar). Initial levels of gill Na+,K(+)-ATPase activity were elevated in chum salmon, which normally migrate as fry. Cortisol (10 micrograms/ml for 4 days in vitro) increased gill Na+,K(+)-ATPase activity in chum salmon fry (48% above initial levels), had a limited but significant effect in chinook salmon fry, and had no effect in coho and Atlantic salmon fry. In an in vivo experiment, Atlantic salmon previously exposed to simulated natural photoperiod (SNP) and continuous light (L24) received four cortisol injections of 2 micrograms.g-1 every third day. SNP fish responded with increased gill Na+,K(+)-ATPase activity (+66%), whereas L24 fish were not affected. Atlantic salmon presmolts with initially low levels of gill Na+,K(+)-ATPase activity responded to cortisol in vitro, whereas smolts with initially high levels of gill Na+,K(+)-ATPase activity were unresponsive.(ABSTRACT TRUNCATED AT 250 WORDS)
Gen Comp Endocrinol 1991 Nov
PMID:Developmental differences in the responsiveness of gill Na+,K(+)-ATPase to cortisol in salmonids. 166 99

1. The inhibitory actions of two class IB antiarrhythmics, lidocaine and tocainide, on Mg(2+)-dependent ATP hydrolysis by myocardial Na(+)-K(+)-ATPase (EC 3.6.1.3), were tested in guinea-pig heart preparations incubated in media containing 2.5, 5.0 and 10 mM K+. 2. The IC50 values for lidocaine were 2.4 +/- 0.4 mM at 2.5, 4.1 +/- 0.8 mM at 5.0 and 5.3 +/- 0.5 mM at 10 mM K+. The corresponding IC20 values were 0.82 +/- 0.12 mM at 2.5, 1.3 +/- 0.2 mM at 5.0 and 1.7 +/- 0.4 mM at 10.0 mM K+ respectively. Tocainide exerted similar action with IC50 values of 3.1 +/- 0.9 mM at 2.5, 7.6 +/- 1.4 mM at 5.0 and 15.5 +/- 1.6 mM at 10.0 mM K+ and IC20 values of 0.71 +/- 0.19 at 2.5, 2.7 +/- 0.5 mM at 5.0 and 12.3 +/- 1.2 mM at 10.0 mM K+ respectively. 3. Thus, the inhibitory potencies of the drugs on myocardial Na(+)-K(+)-ATPase activity increased significantly with reduction in the K+ concentration. These results demonstrate therefore that the inhibitory actions of both lidocaine and tocainide depend on the K+ concentration of the incubation medium. 4. These findings may be indicative of the importance of K+ in some of the cardiac effects of the antiarrhythmic agents, particularly their tendency to induce or enhance already existing cardiac arrhythmias.
Gen Pharmacol 1991
PMID:The effect of modifying potassium concentration on the inhibition of myocardial Na(+)-K(+)-ATPase by two class IB antiarrhythmic drugs: lidocaine and tocainide. 166 1

The in vitro influence of substance P (SP) C- and N-terminal fragments on the Na+,K(+)-ATPase and Ca2+,Mg2(+)-ATPase and monoamine oxidase (MAO) from synaptosomal membrane and extra-synaptosomal mitochondria were studied. The obtained results indicate: 1. C-terminal fragment of SP (SP6-11) in 10 microM concentration stimulates the Ca2+,Mg2(+)-ATPase activities from cerebral cortex and hippocampus. Na+,K(+)-ATPase from cerebral cortex is hardly sensitive to the action of this fragment. 2. N-terminal fragment of SP (SP1-5) in 10 microM concentration increases Na+,K(+)-ATPase activity from cerebral cortex and hippocampus. 3. N-terminal tetrapeptide (SP1-4) exerts no influence on ATPases independently from their brain localization. 4. The activity of monoamine oxidase after use of C- and N-terminal fragments is unchanged.
Gen Pharmacol 1990
PMID:Effects of N- and C-terminal fragments of substance P on ATPase and monoamine oxidase activities in rat brain. 169 30

Plasma membrane ATPase activity of Saccharomyces cerevisiae IGC 3507III grown in the presence of the lipophilic acid octanoic acid [4-50 mg l-1 (0.03-0.35 mM), pH 4.0] was 1.5-fold higher than that in cells grown in its absence. The Km for ATP, the pH profile and the sensitivity to orthovanadate of the basal and the activated forms of the membrane ATPase were identical. This activation was closely associated with a decrease in the biomass yield and an increase in the ethanol yield, and was rapidly reversed in vivo after removal of the acid. However, the activated level was preserved when membranes were extracted and subjected to manipulations which eliminated or decreased octanoic acid incorporation in the plasma membrane. The activity of the basal plasma membrane ATPase in the total membrane fraction was slightly increased by incubation at pH 6.5 with octanoic acid at 100 mg l-1 or less (2.4 mg acid form plus 97.6 mg octanoate ion l-1). However, destruction of the permeability barrier between the enzyme and its substrate could not explain the in vivo activation. A role for plasma membrane ATPase activation in the regulation of the intracellular pH (pHi) of cells grown with octanoic acid was not proven.
J Gen Microbiol 1991 Mar
PMID:Activation of plasma membrane ATPase of Saccharomyces cerevisiae by octanoic acid. 182 36

Plasma membrane Ca2(+)-ATPase of Saccharomyces cerevisiae was solubilized and partially purified by calmodulin-affinity chromatography. The activity of Ca2(+)-ATPase isolated from MATa cells was inhibited by physiological concentrations of the mating pheromone alpha-factor in a dose-dependent manner. The enzyme prepared from a receptor-deficient sterile mutant cells (delta ste-2) was similarly inhibited by alpha-factor, but the enzyme from MAT alpha cells was resistant to the mating pheromone. We suggest that the inhibition may be involved in the alpha-factor-induced increase of Ca2+ uptake reaction of MATa cells.
J Gen Microbiol 1991 Jan
PMID:Inhibition of membrane Ca2(+)-ATPase of Saccharomyces cerevisiae by mating pheromone alpha-factor in vitro. 182 96


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