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)

1. Ouabain-sensitive 86Rb+ uptake by tissue preparations has been used as an estimate of Na+ pump activity. This uptake, however, may be a measure of the Na+ influx rate, rather than capacity of the Na+ pump, since intracellular Na+ concentration is a determinant of the active Na+/Rb+ exchange reaction under certain conditions. This aspect was examined by studying the effect of altered Na+ influx rate on ouabain-sensitive 86Rb+ uptake in atrial preparations of guinea pig hearts. 2. Electrical stimulation markedly enhanced ouabain-sensitive 86Rb+ uptake without affecting nonspecific, ouabain-insensitive uptake. Paired-pulse stimulation studies indicate that the stimulation-induced enhancement of 86Rb+ uptake is due to membrane depolarizations, and hence related to the rate of Na+ influx. 3. Alterations in the extracellular Ca2+ concentration failed to affect the 86Rb+ uptake indicating that the force of contraction does not influence 86Rb+ uptake. 4. Reduced Na+ influx by low extracellular Na+ concentration decreased 86Rb+ uptake, and an increased Na+ influx by a Na+-specific ionophore, monensin, enhanced 86Rb+ uptake in quiescent atria. 5. Grayanotoxins, agents that increase transmembrane Na+ influx, and high concentrations of monensin appear to have inhibitory effects on ouabain-sensitive 86Rb+ uptake in electrically stimulated and in quiescent atria. 6. Electrical stimulation or monensin enhanced ouabain binding to (Na+ + K+)-ATPase and also increased the potency of ouabain to inhibit 86Rb+ uptake indicating that the intracellular Na+ available to the Na+ pump is increased under these conditions. 7. The ouabain-sensitive 86Rb+ uptake in electrically stimulated atria was less sensitive to alterations in the extracellular Na+ concentration, temperature and monensin than that in quiescent atria. 8. These results indicate that the rate of Na+ influx is the primary determinant of ouabain-sensitive 86Rb+ uptake in isolated atria. Electrical stimulation most effectively increases the Na+ available to the Na+ pump system. The ouabain-sensitive 86Rb+ uptake by atrial preparations under electrical stimulation at a relatively high frequency seems to represent the maximal capacity of the Na+ pump in this tissue.
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PMID:Sodium influx rate and ouabain-sensitive rubidium uptake in isolated guinea pig atria. 47 7

1. The Na+ and Cl- fluxes across opercular epithelia from sea water-adapted Fundulus heteroclitus were measured in vitro under open-circuit conditions while bathed on the mucosa with sea water and the serosa with Ringer solution. 2. The mean predicted Na+ flux ratio was 0.94 +/- 0.08 and the observed ratio was 1.14 +/- 0.12 (n = 15; mean +/- S.E. of mean). The difference in these means was not significant (P greater than 0.20). The mean predicted Cl- flux ratio was 11.4 +/- 0.9 and the mean observed ratio was 1.38 +/- 0.27 (n = 10). The difference in these means was significant (P less than 0.001). 3. Ouabain, at 10(-6) M in the serosal solution, produced a significant (P less than 0.01) reduction in the Na+ efflux while having no significant (P greater than 0.40) effect on the Na+ influx. The agreement between the predicted (1.70 +/- 0.14) and observed (1.72 +/- 0.18) Na+ flux ratios after ouabain treatment suggested that this effect could be completely attributed to the depolarization of the epithelium secondary to ATPase inhibition. 4. beta-adrenergic activation by isoprenaline stimulated the Cl- efflux 24.2% and alpha-adrenergic activation by noradrenaline inhibited the Cl- efflux 66.5%. These changes occurred oppositely to those predicted by the changes in the electrical gradient produced by these agents, while the changes in the Cl- influxes corresponded to the electrical changes. Short-circuit experiments confirmed these effects on the Cl- efflux and the lack of effects on the Cl- influx. 5. The results suggested that Na+ was near theromodynamic equilibrium and that the unidirectional fluxes were passive. The effects of alpha- and beta-adrenergic activation suggested that the active Cl- secretion may be antagonistically regulated by catecholamines.
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PMID:Open-circuit sodium and chloride fluxes across isolated opercular epithelia from the teleost Fundulus heteroclitus. 51 53

Factors that determine the interaction of ouabain with the positive inotropic receptor were examined in isolated perfused guinea-pig hearts. The hearts were exposed to ouabain during a perfusion with a modified Krebs-Henseleit solution. The interaction of ouabain with the inotropic receptors under those conditions was estimated by subsequently perfusing the heart with a regular Krebs-Henseleit solution and monitoring the resting and developed tension. Ouabain failed to cause an increase in the force of contraction when the cardiac tissue was exposed to this agent in the absence of Na+ and Ca2+ either in the presence of a low or high concentration of K+. The absence of Ca2+ or the lack of contraction was not responsible for the failure of ouabain to interact with the inotropic receptor, since the exposure of cardiac tissue to ouabain in a Ca,+-free medium containing Na+ resulted in a development of the positive inotropic effect. Thus, ouabain does not interact with its inotropic receptor in the absence of Na+. The properties of the ouabain-receptor interaction resemble those of ouabain binding to Na+, K+-ATPase. In addition, ouabain increases the mobility of superficially bound Ca2+.
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PMID:Sodium ions and the development of the inotropic action of ouabain in guinea-pig heart. 52 57

1. Explants of mammary tissue from pseudopregnant rabbits were cultured at 37 degrees C in air for 24-48h in Medium 199 buffered with 20mm-Hepes [4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid]. The medium contained insulin and corticosterone, or insulin, corticosterone and sheep prolactin in the presence or absence of ouabain, an inhibitor of Na(+)/K(+)-dependent adenosine triphosphatase. The responses of explants were assessed histologically, by measuring the tissue concentration of K(+), and by rates of synthesis of RNA, protein and fatty acids. The effect of ouabain on Na(+) and K(+) concentrations in slices of lactating rabbit mammary-gland tissue incubated for 1h at 37 degrees C in Krebs bicarbonate buffer was also studied. 2. Prolactin increased the concentration of K(+) in mammary explants, an effect prevented by ouabain. In slices of lactating tissue, there was a linear relationship between the log dose of ouabain (from 0.1 to 10mum) and increased Na(+) and decreased K(+) concentrations in the tissue. 3. Ouabain at concentrations up to 1mum did not affect the rate of synthesis of RNA, protein or fatty acids by explants cultured with insulin and corticosterone. By contrast, the stimulatory effect of prolactin on protein synthesis was diminished and the induction of medium-chain fatty acid synthesis by prolactin was almost abolished. RNA synthesis was unaffected. Histological examination showed no tissue damage by 1mum-ouabain. 4. Explants cultured in the presence of 2mum-ouabain for 24h retained their ability to respond to prolactin when the ouabain was removed from the culture medium. Between 24 and 48h they showed responses to prolactin of a magnitude similar to those of explants never exposed to ouabain. 5. These results show that a fully functional Na(+)/K(+)-dependent adenosine triphosphatase system is necessary for prolactin to promote secretory activity in rabbit mammary gland.
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PMID:Inhibition by low concentrations of ouabain of prolactin-induced lactogenesis in rabbit mammary-gland explants. 56 78

1. Low levels of insuling stimulate transendothelial fluid transport from preswollen stroma to aqueous in rabbit corneal preparations. The rate of stromal thinning at the end of the first hour averages 30% faster with insulin, 3.5 x 10(-22) M (4.8 micromicron/ml.), than that of the paired control. This concentration is about the physiological level in rabbit aqueous. 2. The stimulation with insulin is transient. Rates of thinning average higher but not significantly different from control rates by the second hour. 3. High levels of insulin between 3.5 x 10(-9) M (480 micromicron/ml.) and 2.0 x 10(-6) M (2.75 X 10(5) micromicron/ml.) inhibit fluid transport. The inhibition at the low end of this range of concentrations becomes more pronounced with longer perfusion times but appears not to exceed ca. 50% of the control rate. 4. Ouabain also induces a biphasic effect on fluid transport which is characteristically different from that with insulin. The maximal stimulation observed at all times occurred with a fixed concentration of 10(-10) M. The stimulation is not transient but increases throughout the duration of the perfusion; the average rate is elevated 50% above the control rate by the third hour. 5. The transition from a stimulatory to an inhibitory effect occurs consistently at ca. 10(-8) M with ouabain, while a similar transition with insulin occurs at ca. 10(-9) M and appears to shift towards slightly higher concentrations during a 3 hr perfusion period. 6. Inhibition of fluid transport with ouabain, 3 x 10(-7) M, is increased from ca. 50% after 1 hr to more than 70% at the end of the third hour of perfusion. 7. The combined presence of stimulatory concentrations of ouabain and insulin affects tromal thinning in a manner resembling the effect of ouabain alone more than that of insulin; additive effects could not be discriminated. Progressively raising the concentration of insulin to a level (10(-8) M) that alone inhibits stromal thinning, ultimately abolishes the stimulatory effect of ouabain. Based on other evidence and current models of drug/hormone-membrane interaction, these results can be interpreted to indicate a concentration-dependent interaction between receptor complexes of ouabain and insulin with (Na+ + K+)-ATPase.
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PMID:Biphasic effects of insulin and ouabain on fluid transport across rabbit corneal endothelium. 63 30

Ouabain-sensitive uptake of 86Rb+ (an analogue of K+) was enhanced in L-cells that had been treated with 25-hydroxycholesterol or 7-ketocholesterol in order to deplete their sterol concentration. Ouabain-insensitive Rb+ efflux also increased in the sterol-depleted cells and the intracellular concentration of K+ diminished while the concentration of Na+ increased. All of these effects of 25-hydroxycholesterol were counteracted by the addition of mevalonate to the culture medium. Despite the evidence for increased active Rb+ transport in the 25-hydroxycholesterol-treated cells, the level of sodium and potassium ion-activated adenosine triphosphatase ((Na+ + K+)-activated ATPase) activity measured in homogenates and plasma membrane preparations from the treated cells was not significantly different from the control values. Rb+ uptake was more sensitive to ouabain inhibition in sterol-depleted cells than in control cells, although ATPase activity in plasma membrane fractions isolated from treated cells was not more sensitive to ouabain inhibition than was that from control cells. It is possible that the ability of the oxygenated sterols to inhibit DNA synthesis and cell division (Kandutsch, A. A., and Chen, H. W. (1977) J. Biol. Chem. 252, 409-415) is related to their effects upon cellular ion transport.
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PMID:Alteration of 86Rb+ influx and efflux following depletion of membrane sterol in L-cells. 64 Oct 62

The morphological changes following superfusion of the cat cerebral cortex with ouabain were studied. Autoradiography of [3H]ouabain was performed to study drug distribution. The resulting lesion consists of an upper vacuolated layer which is distinctly separated from an underlying region containing dark neurones. Ouabain is confined to the vacuolated layer. Swelling of apical dendrites and many presynaptic terminals are the main morphological changes occurring in the vacuolar layer. Depletion of synaptic vesicles, clustering of vesicles around the synaptic membrane, and the production of coated vesicles and cisternae are further changes found within presynaptic endings. Whilst swelling of fibrous astrocytes within the glialimitans occurs, this is not true of astrocytic processes elsewhere in ouabain exposed regions. Regions containing dark neurones are characterised by a general swelling of astroglial processes. The results strongly suggest that apical dendrites and presynaptic endings possess high activities of Na+, K+-ATPase whereas the activity on astroglial processes within the neuropil is relatively low. Astroglial swelling in areas of dark neurones is produced by some change in the chemical milieu surrounding the processes which appears unrelated to Na+, K+-ATPase inhibition.
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PMID:Morphological changes in the cat cerebral cortex produced by superfusion of ouabain. 65 38

Stria vascularis from guinea pig cochleae was incubated in vitro to determine its metabolic response to variations in substrate and ion composition of the incubation medium. The respiratory rate at 37 degrees C in a medium containing glucose and pyruvate as substrate was 17.3 +/- 1.33 (SEM, n = 51) microliter O2/mg dry weight-hour. The stria could not maintain constant respiration by relying solely upon endogenous fuel stores. With substrate supplied, the ATP level could be maintained at about 73% of that existing in vivo. Glucose appears to be an adequate substrate for stria in vitro since glutamate, pyruvate, and fumarate did not increase the respiratory rate. Succinate increased respiration markedly but did not increase the ATP level. Ouabain (10(-4) M) caused a 48% decrease in the respiratory rate. Incubation in Na+-free and K"-free medium, each resulted in irreversible decrease of respiratory rate comparable to (or greater than) that caused by ouabain. These data are in accord with the high activity of Na+-K+-ATPase in the stria and the pronounced sensitivity of the endolymphatic potential to ouabain.
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PMID:Respiratory rate and ATP content of stria vascularis of guinea pig in vitro. 71 73

Cells of a transformed Syrian hamster line, BP6T, were synchronized by a period of growth in low serum with a subsequent blockage of the cells at the G1/S boundary by hydroxyurea. This method provided cells with nearly 100% synchrony, although approximately 20% of the cells were non-cycling. The cells were then treated with 10(-5) M 5-bromodeoxyuridine for 1 of 5 1-h periods during the S phase and subsequently irradiated with near-ultraviolet light for 5 min. The BrdU plus irradiation treatment induced 6-thioguanine- and ouabain-resistant mutants while BrdU alone or irradiation alone was not mutagenic. 6-Thioguanine-resistant mutants were induced only during early S phase by BrdU plus irradiation treatment. Ouabain-resistant mutants, however, were induced in a biphasic pattern, during early S phase and also during late S phase. The induction of ouabain-resistant mutants at two distinct periods of S phase suggests the presence of two loci for the gene(s) of Na+/K+ ATPase.
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PMID:Induction of 6-thioguanine- and ouabain-resistant mutations in synchronized Syrian hamster cell cultures during different periods of the S phase. 74 10

Rat submandibular gland slices, incubated in continuously-gassed Krebs-Ringer bicarbonate buffer, were shown to release K+ in response to alpha-adrenergic and muscarinic cholinergic stimulation. The system employed the specific alpha-, beta-adrenergic and cholinergic receptor-blocking agents phentolamine, propranolol and atropine, respectively, in combination with the agonists L-epinephrine and carbamylcholine both of which required the presence of Ca2+ for their effect. The introduction of Ca2+ into the cell via the ionophore A23187, with all neurotransmitter receptors blocked, resulted in K+ release. Ouabain also allowed extensive K+ release which was in addition to, and hence independent of, that elicited by epinephrine and carbamylcholine. Ethacrynic acid, a potent inhibitor of salivary secretion in vivo, had no influence on K+ movement. K+ was released by both physalaemin and an eledoisin-related peptide independently of normal neurotransmitter receptors. The activity of the eledoisin-related peptide did not require the presence of extracellular Ca2+. The implication of cyclic GMP at some stage of K+ release was suggested by experiments with a phosphodiesterase inhibitor. The results support an hypothesis where the initial stimulus at either alpha-adrenergic or muscarinic cholinergic receptors causes an immediate permeability change such that Ca2+ enters the cells resulting in K+ release. The loss of K+ is quickly countered by the ouabain-sensitive (Na+ + K+) ATPase which would be activated by the lowered intracellular K+ levels.
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PMID:Potassium release from submandibular salivary gland in vitro. 85 69


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