Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between Na-K-ATPase activity and p-aminohippurate (PAH) transport was examined in renal cortical slices of mixed-breed rabbits by using ouabain to vary the level of Na-K-ATPase activity. Ouabain increased passive PAH uptake, measured in the presence of probenecid. Slice homogenate Na-K-ATPase activity was inhibited by 50% with about 2 X 10(-6) M ouabain. When the concentration was 10(-5) M or above, active PAH uptake was inhibited. Lower concentrations (10(-7) and 10(-6) M) of ouabain stimulated active PAH uptake. Acetate stimulated PAH uptake when medium ouabain was less than 10(-4) M. Ouabain, 10(-5) M and higher, caused intracellular K+ to fall and Na+ to rise. The changes in active PAH uptake observed with ouabain correlated much better with changes in intracellular K+ or Na+ levels (P less than 0.01) than with changes in slice homogenate Na-K-ATPase activity. Vmax for active PAH uptake decreased with 5 X 10(-5) M ouabain, and tended to increase with 10(-7) M ouabain. Ouabain did not alter Km for active PAH uptake. The data support the hypothesis that there is a functional link between active PAH transport and Na-K-ATPase activity. This linkage may be an indirect one mediated by changes in intracellular cation concentrations.
 ...
PMID:Relationship between PAH transport and Na-K-ATPase activity in the rabbit kidney. 21 77

1. Concentrations of 0.1-10 mM Ouabain do not affect oscillating contractions, when applied externally in physiological solutions. 2. Ouabain has no effect, when applied in solutions of increased sodium- (100 mM) and lowered potassium-concentration (0.1 or zero mM). 3. De novo generation of oscillating contractions in protoplasmic drops is not suppressed in Ouabain-solutions. 4. Biochemical studies of Na-K-ATPase did not show any Ouabain sensitive ATPase-activity. 5. Reaction of veins on high concentrations (300 mosm) is discussed as to be a physical effect. 6. It is concluded that no Na-K-ATPase is engaged in triggering oscillating contraction automaticity.
 ...
PMID:Oscillating contractions in protoplasmic strands of Physarum: effects of externally applied ouabain, sodium-, potassium- and calcium-ions. 22 90

The morphological aspects of spermatogenesis are well described in many mammalian species, but functional changes are not completely understood. Electrophysiological parameters were investigated in primary spermatocytes and early and late spermatids isolated from the seminiferous tubules of the mouse. Substantial changes were not detected in membrane potential between different developmental stages. Membrane potential was dependent on both potassium and sodium ion concentration gradients, but not on chloride gradients. The ratio of the permeabilities PNa/Pk varied according to the extracellular concentrations of sodium and potassium. Ouabain, a specific inhibitor of Na+, K+-activated ATPase, produced a maximal reduction in membrane potential of 20%. Comparisons were drawn between differentiating germ cells and previously determined properties of mature spermatozoa.
 ...
PMID:Electrophysiology of differentiating mouse spermatozoa. 22 83

(3H)-Ouabain binding to liver and kidney preparations was utilized to estimate the number of Na+, K+-ATPase enzyme units in livers and kidneys from rats fed 2% corn oil supplemented or fat-free diets. The specific (3H)-ouabain binding in liver and kidney preparations from fatty acid deficient rats was increased approximately 40%, but the affinity of the binding sites for ouabain (Kd-value) remained unchanged. The increased concentration of Na+, K+-ATPase enzyme units observed in the essential fatty acid deficient rats may contribute to the reduced body fat accumulation and elevated heat production observed in these animals.
 ...
PMID:Increase in Na+, K+ -ATPase enzyme units in liver and kidneys from essential fatty acid deficient rats. 22 71

Effects of vanadate on ouabain binding and inhibition of sodium and potassium adenosine triphosphatase (Na+ + K+)-ATPase) were investigated under various ionic conditions. 1. Vanadate facilitated ouabain binding to (Na+ + K+)-ATPase in the presence of Mg2+ and this facilitation was partially reversed by catechol. 2. Vanadate antagonized the ability of high concentrations of NaCl to inhibit ouabain binding in the presence of magnesium. 3. Ouabain binding to the vanadate-enzyme complex, formed from magnesium and vanadate, was more sensitive to depression by potassium than that to the phosphoenzyme formed from magnesium and inorganic phosphate. 4. Preincubation of (Na+ + K+)-ATPase with vanadate in the presence of magnesium initially formed a potassium-insensitive complex as shown by a rapid initial rate of ouabain binding. However, within 5 min potassium overcame the vanadate potentiation of ouabain binding regardless of the order in which it was added to the reaction mixture. 5. Under conditions of enzyme turnover, vanadate failed to antagonize the inhibitory power of ouabain despite the presence of a high concentration of potassium. This suggests a possible relationship between the sensitivity of the sodium pump in various tissues to the cardiac glycosides and intracellular vanadate concentrations.
 ...
PMID:Effects of vanadate on ouabain binding and inhibition of (Na+ + K+)-ATPase. 22 60

The relation between active chloride secretion and Na-K-ATPase activity was studied in the isolated perfused rectal gland of Squalus acanthias stimulated by cAMP and theophylline. Ouabain inhibited both secretion and oxygen uptake in stimulated glands. Stimulation of chloride secretion by cAMP and theophylline resulted in a six- to sevenfold rise in ouabain-inhibitable oxygen consumption. Intracellular sodium concentration decreased while intracellular potassium rose. These findings suggest activation of Na-K-ATPase. On the other hand, the activity of Na-K-ATPase in whole homogenates of rectal gland tissue was not increased after cAMP stimulation of the perfused gland, nor was ouabain binding increased. Calculated intracellular chloride concentration fell after secretion was stimulated in a way consistent with an action of cAMP to increase luminal permeability to chloride.
 ...
PMID:Indirect evidence for enhancement of Na-K-ATPase activity with stimulation of rectal gland secretion. 22 37

Analysis of the cation composition of growing Mycoplasma mycoides var. Capri indicates that these organisms have a high intracellular K+ concentration (Ki: 200--300 mM) which greatly exceeds that of the growth medium, and a low Na+ concentration (Na+i: 20 mM). Unlike Na+i,K+i varies with cell aging. The K+ transport properties studied in washed organisms resuspended in buffered saline solution show that cells maintain a steady and large K+ concentration gradient across their membrane at the expense of metabolic energy mainly derived from glycolysis. In starved cells, K+i decreases and is partially compensated by a gain in Na+. This substitution completely reverses when metabolic substrate is added (K+ reaccumulation process). Kinetic analysis of K+ movement in cells with steady K+ level shows that most of K+ influx is mediated by an autologous K+-K+ exchange mechanism. On the other hand, during K+ reaccumulation by K+-depleted cells, a different mechanism (a K+ uptake mechanism) with higher transport capacity and affinity drives the net K+ influx. Both mechanisms are energy-dependent. Ouabain and anoxia have no effect on K+ transport mechanisms; in contrast, both processes are completely blocked by dicyclohexylcarbodiimide, an inhibitor of the Mg2+ -dependent ATPase activity.
 ...
PMID:Active K+ transport in Mycoplasma mycoides var. Capri. Net and unidirectional K+ movements. 37 56

The effects of various interventions on the frequency-dependent increases in the contractility of the papillary muscles of monkeys were investigated. Ouabain (10(-6)M) and KCl-free Krebs-Ringer solution, which are known to inhibit membrane Na+,K+-ATPase (EC 3.6.1.3), abolished the frequency-dependent increases in the contractility of the papillary muscles. Epinephrine (4.5 X 10(8)M) or quinidine (1.3 X 10(-5)M), which are known not to inhibit the membrane Na+,K-ATPase at these concentrations, did not alter the frequency-dependent increases in the contractility. These results indicate that the frequency-dependent increases in the contractility might be mediated through an inhibition of the sarcolemmal Na+,K+-ATPase.
 ...
PMID:Possible mechanism for the frequency-dependent increases in the cardiac contraction in monkey. 40 75

Potassium (K+) is a vasoactive agent and is released from muscle cells during exercise. A simple diffusion model does not predict the time course of K+ efflux during exercise, which decreases as the exercise progresses. We constructed a mathematical model using the concept of an active Na+-K+ ion pump to account for the decreased efflux during and uptake after exercise. Passive fluxes are calculated by the Nernst equation. Active fluxes are constrained to balance these passive fluxes at rest. The pump activity increases as either extracellular K+ or intracellular Na+ concentration increases. To test the model, the venous K+ efflux profile was simulated for direct stimulation (4/s) of the anterior calf mus cles of dogs. The model simulated the K+ release during the stimulation period and [K+] undershoot after the stimulation. The active Na+-K+ ATPase transport concept used in the model was further tested by observing K+ efflux after administration of ouabain. Ouabain infusion decreased K+ uptake during exercise slightly and abolished [K+] undershoot after the stimulation. These experimental data were matched by the model only if a discontinuous effect of ouabain is assumed. This suggests that ouabain may more completely block the sensitivity of the pump to intracellular [Na+] than to extracellular [K+].
 ...
PMID:A model of potassium ion efflux during exercise of skeletal muscle. 43 91

1. The fluxes of Na were measured on isolated coprodeal mucosa at 1--220 mM-Na from hens on low (L) and high (H) Na diets with the purpose of finding the location and characteristics of Na sites activated in the cellular pathway by L. 2. The influx across the brush border, JNamc, and the transmural fluxes, JNasm and JNams, were determined. Effects on these fluxes of ouabain, 10(-3) M in the serosal solution, and amiloride, 10(-4) M in the mucosal solution, were studied for both dietary states. 3. JNamc was 5--22 (L) and 0--0.8 (H) muequiv/cm2.hr at 130 mM-Na corrected for the paracellular flux of Na. The JNamc (H) is tenfold smaller than found by Choshniak, Munck & Skadhauge (1977). This discrepancy is at present inexplicable. Amiloride completely inhibited JNamc (L). Preincubation in 0 or 130 mM-Na had no effect on JNamc. Ouabain reduced JNamc (L) by only about 37% after preincubation at 130 mM-Na. The Kt of JNamc was 5.1 (L) and 50.6 (H) mM-Na. 4. JNasm was 50 (H) and 61 (L) n-equiv/cm2.hr at 6.5 mM-Na. Ouabain increased JNasm by 360% in the low Na state. The increased JNasm was inhibited 74--100% by amiloride. This is interpreted as a ouabain induced Na-Na exchange at the basolateral Na-K-ATPase and an almost complete block of JNacm by amiloride. A similar exchange of Na at the basolateral membrane in the high-Na state was revealed by 'opening' the brush border for Na with monensin added to the mucosal solution. Amiloride in itself prevented a 50% recirculation of Na via the paracellular route and back across the cells in the low Na state. 5. JNams was 5.6 (L) muequiv/cm2.hr and 187 (L) microA/cm2 at 6.5 mM-Na. Amiloride reduced these values to 0.4 muequiv/cm2.hr and 5.8 microA/cm2. On addition of amiloride the transmural resistance in (L) coprodea at 130 mM-Na increased from 140 to 190 and it remained unchanged at 260 omega cm2 in (H) coprodea. The resistance of (L) birds, 163, was not affected by ouabain, 166 (L) omega cm2. 6. 20:1 NaCl dilution potentials at the mucosal side of 17--18 mV (L) and nearly zero (H) had half-times around 1 sec. Amiloride eliminated completely these diffusion potentials. The short half-time indicates a location in the brush border of sodium specific sites induced by the low-Na diet. This conclusion is oppsite to that described by Choshniak et al. (1977). 7. Ion selectivity, voltage--current and conductance--concentration relations in the presence of amiloride indicated a weakly cation selective and highly hydrated pathway, which was also thick and with neutral sites. This fits a paracellular route with the limiting barrier for ions at the tight junction.
 ...
PMID:Sodium transport in the hen lower intestine. induction of sodium sites in the brush border by a low sodium diet. 46 29


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>