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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activity of the electrolyte transport enzyme, sodium, potassium-activated adenosine triphosphatase (Na+,K+-ATPase), in the gills of the pinfish, Lagodon rhomboides, increased markedly following transfer of fish from brackish water to seawater. Cytochemical localization of Na+,K+-ATPase via its potassium-dependent phosphatase (K+-NPPase) activity in the branchial epithelium of pinfish adapted to seawater demonstrated that chloride cells are the major sites for the enzyme. Subcellularly, the heaviest depositions of reaction product were observed lining the cytoplasmic membrane surfaces of the labyrinth of anastomosing plasma membrane tubules that ramifies throughout the chloride cell cytoplasm. Enzyme activity was demonstrated also on the cytoplasmic surface of the apical crypt membrane and on the cytoplasmic surfaces of vesicles in the cytoplasm subjacent to the crypt. Deletion of potassium from the cytochemical incubation medium or inclusion of 10 mM ouabain abolished the reaction products associated with these membranes. The significance of these cytochemical results is discussed with reference to current hypotheses of chloride cell function.
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PMID:Ultracytochemical localization of Na+,K+-activated ATPase in chloride cells from the gills of a euryhaline teleost. 21 85

The interactions of gadolinium ion, lithium, and two substrate analogues, beta,gamma-imido-ATP (AMP-PNP) and tridentate CrATP, with the calcium ion transport adenosine triphosphatase (Ca2+-ATPase) of rabbit muscle sarcoplasmic reticulum have been examined by using 7Li+ NMR, water proton NMR, and Gd3+ EPR studies. Steady-state phosphorylation studies indicate that Gd3+ binds to the Ca2+ activator sites on the enzyme with an affinity which is approximately 10 times greater than that of Ca2+. 7Li+, which activates the Ca2+-ATPase in place of K+, has been found to be a suitable nucleus for probing the active sites of monovalent cation-requiring enzymes. 7Li+ nuclear relaxation studies demonstrate that the binding of Gd3+ ion to the two Ca2+ sites on Ca2+-ATPase increases the longitudinal relaxation rate (1/T1) of enzyme-bound Li+. The increase in 1/T1 was not observed in the absence of enzyme, indicating that the ATPase enhances the parmagnetic effect of Gd3+ on 1/T1 of 7Li+. Water proton relaxation studies also show that the ATPase binds Gd3+ at two tight-binding sites. Titrations of Gd3+ solutions with Ca2+-ATPase indicate that the tighter of the two Gd3+-binding sites (site 1) provides a ghigher enhancement of water relaxation than the other, weaker Gd3+ site (site 2) and also indicate that the average of the enhancements at the two sites is 7.4. These data, together with a titration of the ATPase with Gd3+ ion, yield enhancements, epsilonB, of 9.4 at site 1 and 5.4 at site 2. Analysis of the frequency dependence of 1/T1 of water indicates that the electron spin relaxation taus of Gd3+ is unusually long (2 X 10(-9) s) and suggests that the Ca2+-binding sites on the ATPase experience a reduced accessiblity of solvent water. This may indicate that the Ca2+ sites on the Ca2+-ATPase are buried or occluded within a cleft or channel in the enzyme. The analysis of the frequency dependence is also consistent with three exchangeable water protons on Gd3+ at site 1 and two fast exchanging water protons at site 2. Addition of the nonhydrolyzing substrate analogues, AMP-PNP and tridenate CrATP, to the enzyme-Gd3+ complex results in a decrease in the observed enhancement, with little change in the dipolar correlation time for Gd3+, consistent with a substrate-induced decrease in the number of fast-exchanging water protons on enzyme-bound Gd3+. From the effect of Gd3+ on 1/T1 of enzyme-bound Li+, Gd3+-Li+ separations of 7.0 and 9.1 A are calculated. On the assumption of a single Li+ site on the enzyme, these distances set an upper limit on the separation between Ca2+ sites on the enzyme of 16.1 A.
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PMID:Lithium-7 nuclear magnetic resonance, water proton nuclear magnetic resonance, and gadolinium electron paramagnetic resonance studies of the sarcoplasmic reticulum calcium ion transport adenosine triphosphatase. 22 3

Growth of Streptococcus faecalis in complex media with various fuel sources appeared to be limited by the rate of supply of adenosine-5' -triphosphate (ATP) at 1 atm and also under 408 atm of hydrostatic pressure. Growth under pressure was energetically inefficient, as indicated by an average cell yield for exponentially growing cultures of only 10.7 g (dry weight) per mol of ATP produced compared with a 1-atm value of 15.6. Use of ATP for pressure-volume work or for turnover of protein, peptidoglycan, or stable ribonucleic acid (RNA) did not appear to be significant causes of growth inefficiency under pressure. In addition, there did not seem to be an increased ATP requirement for ion uptake because cells growing at 408 atm had significantly lower internal K(+) levels than did those growing at 1 atm. Pressure did stimulate the membrane adenosine triphosphatase (ATPase) or S. faecalis at ATP concentrations greater than 0.5 mM. Intracellular ATP levels were found to vary during the culture cycle from about 2.5 mumol/ml of cytoplasmic water for lag-phase or stationary-phase cells to maxima for exponentially growing cells of about 7.5 mumol/ml at 1 atm and 5.5 mumol/ml at 408 atm. N,N'-dicyclohexylcarbodiimide at a 10 muM concentration improved growth efficiency under pressure, as did Mg(2+) or Ca(2+) ions at 50 mM concentration. These agents also enhanced ATP pooling, and it seemed that at least part of the growth inefficiency under pressure was due to increased ATPase activity. In all, it appeared that S. faecalis growing under pressure has somewhat reduced ATP supply but significantly increased demand and that the inhibitory effects of pressure can be interpreted largely in terms of ATP supply and demand.
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PMID:Energetics of streptococcal growth inhibition by hydrostatic pressure. 40 25

The release of lipoteichoic acid and mesosomal vesicles to the supernatant buffer during the formation of spherical, osmotically fragile bodies was studied using Streptococcus faecalis ATCC 9790. Autolytic N-acetylmuramidase action was permitted to take place in exponential-phase cells incubated in a buffer which provides an exceptional degree of osmotic stabilization. Both lipoteichoic acid and mesosomal vesicles were relatively rapidly released to the supernatant buffer. Most of the cellular content of lipoteichoic acid (and mesosomal vesicles) was found in the supernatant buffer at incubation times when the cells still retained over 75% of their cell wall. [14-C]- or [3-H]glycerol was used as a label for both cellular lipoteichoic acids and lipid-glycerol. Glycerol in lipoteichoic acid was quantitated after phenol-water and chloroform-methanol treatments and identified by products of acid hydrolysis and its ability to be precipitated by (i) antibodies specific for the polyglycerol-phosphate backbone, (ii) antibodies to the streptococcal group D antigen, and (iii) concanavalin A. Evidence was obtained that lipoteichoic acid was not associated with isolated mesosomal vesicles. Centrifugation of supernates at 200,000 X g sedimented membranous (mesosomal) vesicles and nearly all of the lipid-glycerol present, whereas essentially all of the lipoteichoic acid remained in the supernatant. The sedimented mesosomal vesicles differed from protoplast membrane in their higher lipid-phosphorus to protein ratio and in the absence of detectable levels of two enzymatic activities found in protoplast membranes, adenosine triphosphatase and polynucleotide phosphorylase. Both types of membranes were found to contain DD-carboxypeptidase and LD-transpeptidase activities at nearly the same specific activities. No evidence was obtained for the association of autolytic N-acetylmuramidase activity with either type of membrane preparation.
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PMID:Cellular localization of lipoteichoic acid in Streptococcus faecalis. 80 56

Ethanol (3%) decreases the potential difference and short-circuit current across the isolated frog skin in chloride Ringer's solution. Unidirectional fluxes of Na and Cl indicate that the drop in short-circuit current is due to an inhibition of the sodium influx. However, ethanol had no effect on the electrical parameters or sodium fluxes, when the frog skin was bathed in chloride-free solutions on both sides or the outside alone. The ethanol response is anion-dependent. In addition, chloride-free media in the inside bathing solution reduced the short-circuit current, indicating a sodium transport pathway which is dependent on chloride and confirming previous data in the literature. Other anions such as sulfate and nitrate could not substitute for chloride. The vasopressin-induced natriferic response and the ethanol effect were found to work independently of each other and different pathways of action are suggested for these agents. The intracellular sodium content of the isolated frog skin epithelium increased and potassium decreased in the presence of the Na-K adenosine triphosphatase inhibitor, ouabain, whereas ethanol or amiloride had no effect. The oxygen consumption of the isolated frog skin was unaffected by up to 10% ethanol. A general metabolic action is probably thus not mediating the response. Urea, in iso-osmotic concentrations to the ethanol, did not mimic its effect. Tritiated water fluxes (in the absence of an osmotic gradient) were reduced by 30% in the presence of 3% ethanol. It is suggested that ethanol may impede the flow of water across frog skin by a physicochemical interaction with membrane pores and the water molecules. The permeability coefficient (Ktrans) for ethanol was found to be 10 times smaller than the Ktrans for water.
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PMID:Effects of ethanol on the permeability of frog skin. 108 5

Methyl isocyanate (MIC) interaction with the rabbit erythrocyte membrane increased the fluidity of the membrane and decreased the osmotic fragility of erythrocytes both in vitro and in vivo in rabbits intoxicated with MIC subcutaneously. MIC inhibited both acetylcholinesterase (AChE) and adenosine triphosphatase (ATPase) activities of erythrocytes dose-dependently in vitro, while in vivo a decreased trend in ATPase activity with unaltered AChE activity was observed. MIC also caused significant decrease in plasma sodium level with corresponding increase in potassium level in rabbits. The observed effects are due to MIC, per se, as the hydrolysis products of MIC, methylamine and N,N'-dimethylurea did not affect the erythrocyte fluidity and enzymes activities both in vitro and in vivo while they increased the osmotic fragility of erythrocytes in vivo in rabbits administered subcutaneously in equimolar concentration to MIC dosage. Inhibition of Na(+)-K(+)-dependent ATPase with altered permeability to cations and also probably water transport of plasma membrane due to MIC interaction are envisaged.
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PMID:Acute toxicity of methyl isocyanate in rabbit: in vitro and in vivo effects on rabbit erythrocyte membrane. 153 91

We have compared the response of proton and water transport to oxytocin treatment in isolated frog skin and urinary bladder epithelia to provide further insights into the nature of water flow and H+ flux across individual apical and basolateral cell membranes. In isolated spontaneous sodium-transporting frog skin epithelia, lowering the pH of the apical solution from 7.4 to 6.4, 5.5, or 4.5 produced a fall in pHi in principal cells which was completely blocked by amiloride (50 microM), indicating that apical Na+ channels are permeable to protons. When sodium transport was blocked by amiloride, the H+ permeability of the apical membranes of principal cells was negligible but increased dramatically after treatment with antidiuretic hormone (ADH). In the latter condition, lowering the pH of the apical solution caused a voltage-dependent intracellular acidification, accompanied by membrane depolarization, and an increase in membrane conductance and transepithelial current. These effects were inhibited by adding Hg2+ (100 microM) or dicyclohexylcarbodiimide (DCCD, 10(-5) M) to the apical bath. Net titratable H+ flux across frog skin was increased from 30 +/- 8 to 115 +/- 18 neq.h-1.cm-2 (n = 8) after oxytocin treatment (at apical pH 5.5 and serosal pH 7.4) and was completely inhibited by DCCD (10(-5) M). The basolateral membranes of the principal cells in frog skin epithelium were found to be spontaneously permeable to H+ and passive electrogenic H+ transport across this membrane was not affected by oxytocin. Lowering the pH of the basolateral bathing solution (pHb) produced an intracellular acidification and membrane depolarization (and an increase in conductance when the normal dominant K+ conductance of this membrane was abolished by Ba2+ 1 mM). These effects of low pHb were blocked by micromolar concentrations of heavy metals (Zn2+, Ni2+, Co2+, Cd2+, and Hg2+). Lowering pHb in the presence of oxytocin (50 mU/ml) produced a transepithelial current (3 microA.cm-2 at pHb 5.5) which was blocked by 100 microM of Hg2+, Zn2+, or Ni2+ at the basolateral side, and by DCCD (10(-5) M) or Hg2+ (100 microM) from the apical side. The net hydroosmotic water flux (JH2O) induced by oxytocin in frog bladder sacs was blocked by inhibitors of H(+)-adenosine triphosphatase (ATPase). Diethylstilbestrol (DES 10(-5) M), oligomycin (10(-8) M), and DCCD (10(-5) M) prevented JH2O when present in the lumen. These effects cannot be attributed to inhibition of metabolism since cyanide (10(-4) M), or 2-deoxyglucose (10(-3) M) had no effect on JH2O.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Common channels for water and protons at apical and basolateral cell membranes of frog skin and urinary bladder epithelia. Effects of oxytocin, heavy metals, and inhibitors of H(+)-adenosine triphosphatase. 164 38

The role of ions and cell membrane function in the pathogenesis of benign and malignant hypertension was investigated in spontaneously hypertensive rats (SHR). Ten-week-old male SHR (n = 50) and SHR treated with deoxycorticosterone acetate (DOCA; n = 70) and 1% NaCl drinking water were studied weekly for 14 weeks. Malignant hypertension developed only in DOCA-salt SHR and was characterised by severe hypertension, failure to thrive and renal fibrinoid necrosis. Fourteen DOCA-salt SHR and one SHR died. Extracellular (serum) and intracellular (erythrocyte and muscle) Na+, K+, Mg2+, Ca2+ and muscle membrane Na+,K(+)-adenosine triphosphatase (ATPase), Ca(2+)-ATPase and Mg(2+)-ATPase were measured at various stages in the development of malignant hypertension. Three developmental phases were defined: benign, premalignant and malignant. DOCA-salt SHR showed persistent hypokalaemia. In the benign phase, there were no differences in Na+, Mg2+ and Ca2+ between SHR and DOCA-salt SHR. In the premalignant phase, serum and erythrocyte Mg2+ and ATPase activity were significantly lower in DOCA-salt SHR compared with SHR. During the late premalignant and malignant phases, intracellular Ca2+ and Na+ were significantly higher in the DOCA-salt SHR compared with SHR. In view of these findings, the abnormalities in DOCA-salt SHR during the early phases of blood pressure elevation could be contributory factors to the development of malignant hypertension.
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PMID:Altered cations and muscle membrane ATPase activity in deoxycorticosterone acetate-salt spontaneously hypertensive rats. 165 84

Nerve polyol content and (Na+,K+)-adenosine triphosphatase (ATPase) activity of nerve homogenates were studied in a colony of rats fed diets containing either 0%, 10%, 20%, or 40% galactose for 4 months. Nerve water and dulcitol content exhibited dose-dependent increases, whereas nerve myo-inositol content declined with increasing dietary galactose. Homogenate (Na+,K+)-ATPase activity increased with increasing galactose consumption of up to 20% dietary intake and thereafter remained consistently elevated at twice the activity of 0% galactose-fed values. Nerves of rats fed 40% galactose were also examined at the light microscope level and showed evidence of both edema and myelin splitting. These data demonstrate that increased nerve water content, dulcitol accumulation, and myo-inositol depletion parallel the previously reported dose-related increase of endoneurial fluid sodium and chloride in nerves of galactose-fed rats and suggest that elevated nerve homogenate (Na+,K+)-ATPase activity may be related to one or more of these consequences of exaggerated polyol pathway flux.
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PMID:Dose-dependent alterations in nerve polyols and (Na+,K+)-ATPase activity in galactose intoxication. 165 47

Enhanced Na+ and water reabsorption by proximal tubular epithelial cells plays an important role in the development of systemic hypertension associated with cyclosporine immunosuppression. Since such Na+ reabsorption is subserved by sodium-potassium adenosine triphosphatase (Na-K ATPase), the current study compared the acute effects of hydrocortisone (H), cyclosporine, and FK506 on cultured LLC-PK1 cell viability and on Na-K ATPase activity. Phospholipase-C (PL-C) activity was also investigated because of its possible regulatory effect on Na-K ATPase activity. Culture medium containing low (5 nM, 4.1 ng/ml) or high (10 nM) concentrations of FK506 plus cyclosporine at 415 microM (500 ng/ml) resulted in cell death, whereas cyclosporine concentrations of 83 microM plus 5 nM or 10 nM FK506, or isolated use of the two drugs at high dosages, did not affect cell viability. As compared with controls, cyclosporine increased Na-K ATPase activity, particularly with addition of H (P less than 0.01). In contrast, FK506 reduced the specific activity of both PL-cyclosporine and Na-K ATPase (P less than 0.001-0.01); addition of H to FK506 resulted in an even greater fall in both the enzyme activities (P less than 0.001). Na-K ATPase activity increased in cell homogenates briefly incubated with cyclosporine in the ATPase reaction mixture (P less than 0.05) while FK506 reduced such enzyme activity (P less than 0.05), suggesting a direct effect of these agents on pump activity. These data in LLC-PK1 cells pocessing proximal tubular epithelial cell characteristics indicate that the combined use of cyclosporine plus FK506 may be very deleterious to viability in such cells. The opposing effects of cyclosporine and FK506 on PL-cyclosporine and Na-K ATPase activities and the possible potentiating effect of H on such responses are speculated to affect Na+ and water homeostasis in a manner that may explain differences in systemic blood pressure due to these agents.
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PMID:Phospholipase-C and Na-K ATPase activation by cyclosporine and FK506 in LLC-PK1, cells. Possible implications in blood pressure regulation. 171 43


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