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PubMed1990

In vivo and in vitro effects of aldrin on rat brain synaptosomal Mg2+ and Na+,K(+)-adenosine triphosphatase.

Aldrin, a chlorinated hydrocarbon, inhibited rat brain synaptosomal membrane-bound Na+,K(+)-adenosine triphosphatase (ATPase) and Mg2(+)-ATPase activities under in vivo and in vitro conditions. Na+,K(+)-ATPase was non-competitively inhibited whereas Mg2(+)-ATPase was inhibited uncompetitively. Arrhenius plots of both these ATPases without aldrin under in vivo and in vitro conditions were found to be linear. In the presence of aldrin, on the other hand, Arrhenius plots of the same ATPases were nonlinear. Slopes of Arrhenius plots of both ATPases under in vivo and in vitro condition were changed with change in temperature with aldrin. The activation energy (AE) of Na+,K(+)-ATPase and Mg2(+)-ATPase activities were changed over the temperature range 15-40 degrees in the presence of aldrin. These results thus suggest that aldrin increases the lipid fluidity of the synaptosomal membrane which may be a cause of inhibition of neuronal membrane-bound Na+,K+ and Mg2(+)-ATPase activities.

Aldrin↗

PubMed1983

Erythrocyte sodium-potassium-stimulated adenosine triphosphatase activity is not related to obesity.

Altered erythrocyte sodium potassium (Na,K)-stimulated adenosine triphosphatase (ATPase) activity has been cited as having pathophysiologic significance in morbidly obese man. Previous studies have failed to consider obese patients after weight loss and, therefore, did not clarify the role of ATPase deficiency as a cause or effect of the obese state. To define more completely the possible alteration of cellular thermogenesis in obesity, a study was made of three groups of people: (1) normal weight controls; (2) morbidly obese; and (3) formerly morbidly obese patients who had lost over 100 pounds after gastric bypass surgery. Erythrocyte ATPase activity was determined by use of an assay that coupled ATPase activity with NADH oxidation in the presence of excess pyruvate kinase, lactic dehydrogenase, and phosphoenolpyruvate. This coupled assay produced a continuous slope so that activity could be calculated from the initial, maximal, linear portion of the decay trace. Results did not demonstrate any statistically significant differences in Na,K-ATPase activity between groups by analysis of variance. A nonsignificant correlation of 0.086 was seen between obesity index and Na,K-ATPase activity. It is concluded that (1) erythrocyte Na,K-ATPase activity is similar in both normal and obese individuals, (2) erythrocyte Na,K-ATPase does not change with weight loss, and (3) therefore, disordered erythrocyte thermogenesis does not have a role in the development or maintenance of obesity.

Adult↗

PubMed1994

Presynaptic ecto- and postsynaptic endo-calcium-adenosine-triphosphatases in synaptosomes: doubts about biochemical interpretation of localization.

Ecto- and endo-Ca-adenosine-triphosphatase (ATPase) activity was identified as electron-dense lead or cerium phosphate precipitate in the rat cortical synaptosomes by transmission electron microscopy and enzyme histochemistry. The formation of the deposit was dependent on the presence of ATP (the substrate), Ca (activator) and levamisole, quercetin or ouabain (inhibitors of different phosphatases and ATPases). Reaction products were found at the external surface of the presynaptic membrane, both surfaces of the postsynaptic membrane, in the synaptic cleft and in the free mitochondrial membranes. In the presence of ATP and the three inhibitors together, the quantity of the precipitate decreased markedly, but we still found some deposit on the external surface of the presynaptic membrane (this activity is probably due to the so-called ecto-ATPase) and on the internal surface of the postsynaptic one (endo-ATPase). The distinction between ecto- and endo-ATPases in biochemical fractions solely upon biochemical differential measurements must be interpreted with caution.

Animals↗

PubMed1978

Denaturation of the tryptic fragments of the calcium (II) adenosine triphosphatase from sarcoplasmic reticulum by guanidinium hydrochloride.

Primary and secondary fragments of the Ca2+-adenosine triphosphatase from sarcoplasmic reticulum are resistant to complete denaturation by guanidinium hydrochloride, a property characteristic of many intrinsic membrane proteins. None of the fragments display a single cooperative transition from ordered structure to random coil suggesting each fragment contains several domains of differing resistance to guanidinium hydrochloride denaturation. The data suggest that the native enzyme has at least three membrane-embedded domains, with an externally accessible link between each.

Alkylation↗

PubMed1985

Aging: effects on sodium- and potassium-activated adenosine triphosphatase activity and ouabain binding sites in rat brain.

Sodium- and potassium-activated adenosine triphosphatase (Na,K-ATPase) activity and [3H]-ouabain binding were examined in homogenates of cerebral cortex, striatum, and hypothalamus of 3-, 8-, and 26-month-old rats to determine if aging-related alterations in energy utilization demonstrated in brain slices and homogenates are potentially associated with alterations in Na,K-ATPase. There were no consistent age-related changes seen in Na,K-ATPase activity, the number of [3H]-ouabain binding sites, or their affinity for ouabain. Moreover, enzyme activities of the two molecular forms of Na,K-ATPase and their inhibition by strophanthidin did not appear to be different in partially purified enzyme preparations obtained from whole brain of 3- and 26-month-old rats. In contrast, the concentration of [3H]-ouabain binding sites was lower in cardiac muscle of senescent rats indicating a reduction in the number of active Na,K-ATPase units. It appears unlikely that aging-related central nervous system changes are associated with alterations in the Na,K-ATPase enzyme system.

Aging↗

PubMed1988

Effects of lead and natriuretic hormone on kinetics of sodium-potassium-activated adenosine triphosphatase: possible relevance to hypertension.

Inhibition of vascular smooth muscle sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase) has been postulated as a central mechanism in enhancing vascular contractility. In the present study, kinetics of inhibition of Na-K-ATPase by lead, ouabain, and natriuretic hormone (NH) was studied in a purified hog cerebral cortex enzyme preparation. Determination of I50 values for lead, ouabain, and NH revealed that NH is the most potent inhibitor of the enzyme system (0.8 x 10(-6) M ouabain equivalents). Kinetic analyses indicated that lead and NH exhibited different inhibitory mechanisms. The inhibition by lead was noncompetitive with respect to potassium and competitive with respect to sodium and MgATP. Natriuretic hormone was noncompetitive with respect to potassium, uncompetitive with respect to MgATP, and exhibited no inhibitory effect with respect to sodium. Synergism between lead and NH in the inhibition of Na-K-ATPase raises the possibility that lead may be a contributory factor in hypertension via this mechanism.

Animals↗

PubMed1989

Veratrine-induced decrease of (Na+ + K+)-adenosine triphosphatase activity in rat brain slices.

The effect of membrane excitability on (Na+ + K+)-adenosine triphosphatase (ATPase) was studied in rat brain slices. The treatment of the brain cortical slices with veratrine for more than 10 min caused a significant decrease of the (Na+ + K+)-ATPase activity. The similar inhibition of the enzyme by veratrine was observed in the hippocampus and hypothalamus, and the veratrine treatment did not affect the sensitivity of the cortical enzyme for ouabain inhibition. These findings suggest that two isozymes of (Na+ + K+)-ATPase are equally inhibited by the treatment. Veratrine inhibited the partial reactions such as Na+-dependent phosphorylation and K+-stimulated phosphatase as well as the specific binding of [3H]ouabain. Agents which increase intracellular Na+ concentration also inhibited the enzyme activity. The effects of veratrine were blocked by Na+-free medium or tetrodotoxin. Low Na+ medium decreased the enzyme activity, and the effect was blocked by amiloride or Ca++-free medium, indicating the involvement of Na+/Ca++ exchange in the inhibition. The decreased activity induced by low Na+ or high K+ medium was restored to the normal level by the subsequent incubation in normal medium. The inhibitory effect of veratrine was dependent on external Ca++, and was blocked by addition of W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide]. A23187 also decreased (Na+ + K+)-ATPase activity in the slices. High Mg++ medium blocked the effect of veratrine but not that of monensin which was not dependent on external Ca++.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Localization of sodium-potassium adenosine triphosphatase in sheep myocardium by immunoelectron microscopy.

Immunohistochemical localization of sodium and potassium dependent adenosine triphosphatase (Na,K-ATPase) employing polyclonal antibodies was carried out on sheep myocardium. The tissue was fixed with glutaraldehyde or a paraformaldehyde/lysine/periodate combination fixative and embedded in different embedding media. Ultrathin sections were labeled with rabbit anti-sheep Na,K-ATPase antiserum followed by sheep anti-rabbit immunoglobulin complexed with colloidal gold. Glycol methacrylate embedded tissue provided good structural preservation and showed specific immunohistochemical labeling. Analysis of the gold particle distribution showed a significantly higher number of Na,K-ATPase immunoreactive sites associated with cell membrane and T-tubules.

Animals↗

PubMed1981

Canrenone as a partial agonist at the digitalis receptor site of sodium-potassium-activated adenosine triphosphatase.

Canrenone, a spironolactone metabolite, was tested for its possible effects on (Na+-K+) adenosine triphosphatase (ATPase) activity [Mg++-dependent, (Na+-K+)-activated ATP phosphohydrolase (E.C.3.6.1.3) and ouabain interaction with the enzyme. Canrenone competitively antagonized the binding of [3H]ouabain to (Na+-K+)ATPase and inhibited (Na+-K+)ATPase activity. The multiple inhibition technique was used to demonstrate that canrenone is a partial inhibitor of (Na+-K+)ATPase, mutually exclusive with respect to ouabain. Comparative studies of the effects of ouabain and canrenone on potassium-dependent p-nitrophenylphosphatase activity (E.C.9.6.1.7) and potassium activation of (Na+-K+)ATPase confirmed that ouabain and canrenone interacted with the same receptor site. The finding that canrenone is a partial agonist may explain the results of previous in vivo studies showing that spironolactone and the allied drug to potassium conrenoate have either a positive inotropic action or an antagonistic effect against digitalis toxicity.

4-Nitrophenylphosphatase↗

PubMed2005

Temperature differentially affects adenosine triphosphatase activity in Hsc70 orthologs from Antarctic and New Zealand notothenioid fishes.

To test the temperature sensitivity of molecular chaperones in poikilothermic animals, we purified the molecular chaperone Hsc70 from 2 closely related notothenioid fishes--the Antarctic species Trematomus bernacchii and the temperate New Zealand species Notothenia angustata--and characterized the effect of temperature on Hsc70 adenosine triphosphatase (ATPase) activity. Hsc70 ATPase activity was measured using [alpha-32P]-adenosine triphosphate (ATP)-based in vitro assays followed by separation of adenylates by thin-layer chromatography. For both species, a significant increase in Hsc70 ATPase activity was observed across a range of temperatures that was ecologically relevant for each respective species. Hsc70 from T bernacchii hydrolyzed 2-fold more ATP than did N angustata Hsc70 at 0 degrees C, suggesting that the Antarctic molecular chaperone may be adapted to function more efficiently at extreme cold temperatures. In addition, Q10 measurements indicate differential temperature sensitivity of the ATPase activity of Hsc70 from these differentially adapted fish that correlates with the temperature niche inhabited by each species. Hsc70 from T bernacchii was relatively temperature insensitive, as indicated by Q10 values calculated near 1.0 across each temperature range measured. In the case of Hsc70 purified from N angustata, Q10 values indicated thermal sensitivity across the temperature range of 0 degrees C to 10 degrees C, with a Q10 of 2.714. However, Hsc70 from both T bernacchii and N angustata exhibited unusually high thermal stabilities with ATPase activity at temperatures that far exceeded temperatures encountered by these fish in nature. Overall, as evidenced by in vitro ATP hydrolysis, Hsc70 from T bernacchii and N angustata displayed biochemical characteristics that were supportive of molecular chaperone function at ecologically relevant temperatures.

Adenosine Triphosphatases↗

PubMed1987

Energy metabolism in canine erythrocytes associated with inherited high Na+- and K+-stimulated adenosine triphosphatase activity.

Energy metabolism in canine erythrocytes associated with inherited high Na+- and K+-stimulated adenosine triphosphatase [(Na,K)-ATPase] activity (HK cells) was compared with that in normal canine erythrocytes (LK cells). Activities of some of the glycolytic enzymes in the HK cells were significantly higher than those in LK cells. The concentrations of adenosine triphosphate (ATP) and glycolytic intermediates in HK cells were almost equal to those in LK cells. Glucose utilization and lactate production by HK cells in vitro and incorporation of [32P]orthophosphate or [14C]glucose into 2,3-diphosphoglycerate in HK cells were higher than in LK cells. Radioactivity of [32P]ATP in HK cells was lower than in LK cells, but increased to approximately that of LK cells when (Na,K)-ATPase of HK cells was completely blocked by ouabain. When HK cells and LK cells were incubated in the absence of glucose, the concentration of ATP in HK cells was decreased more than that of LK cells. Although ouabain reduced the rate of decrease in ATP in HK cells, the decrease in ATP in HK cells was still 2-fold that in LK cells. The half-life of HK cells was about one-half that of LK cells. The results indicated that glycolysis is greater in HK cells than in LK cells, and that the increased glycolysis in HK cells was stimulated by an increased rate of ATP breakdown for active cation transport by the (Na,K)-ATPase and by increased degradation of ATP for some other pathway, eg, glutathione synthesis. Thus, the increased demand for ATP in HK cells might result in shortening the lifespan of HK erythrocytes.

Animals↗

PubMed1999

Effect of artemether on phosphorylase, lactate dehydrogenase, adenosine triphosphatase, and glucosephosphate dehydrogenase of Schistosoma japonicum harbored in mice.

AIM: To study the effect of artemether (Art) on phosphorylase (PP), lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-PDH), and adenosine triphosphatase (ATPase) of S japonicum. METHODS: Mice infected with S. japonicum cercariae for 32-38 d were treated i.g. with Art 100-300 mg.kg-1 and killed 24-72 h after treatment for collection of schistosomes. The activities of PP, LDH, and G-6-PDH were measured by the formation of NADH or NADPH. The activity of ATPase was measured by the rate of release of inorganic phosphate (Pi) from ATP at 37 degrees C. RESULTS: After infected mice were treated i.g. with Art 300 mg.kg-1 for 24-48 h, the activities of total PP and PPa (active form) increased markedly in both male and female worms, while PPb (inactive form) showed no or only a slight increase. At 24-72 h after the above-mentioned mice were treated i.g. with Art 100-300 mg.kg-1, the inhibitory rates of LDH and G-6-PDH were 9%-59% (male) and 41%-75% (female) as well as 22%-42% (male) and 74%-89% (female), respectively. When Art 300 mg.kg-1 was given to infected mice for 24 h, only the activity of Mg(2+)-ATPase showed marked inhibition in both male and female worms. At 48 h, the Ca(2+)-ATPase, Mg(2+)-ATPase, and Na(+)-K(+)-ATPase were all inhibited, the inhibitory rates of 17% (male) and 19% (female), 32% (male) and 48% (female) as well as 29% (male) and 44% (female), respectively. CONCLUSION: In schistosomes, the increase in the activity of AMP-independent PPa induced by Art may enhance the decomposition of glycogen and the inhibition of LDH by Art could reduce the formation of lactate. Moreover, Art exerts a potent inhibition on the G-6-PDH activity of the female S japonicum.

Adenosine Triphosphatases↗

PubMed1980

Intersubunit interactions in proton-translocating adenosine triphosphatase as revealed by hydrogen-exchange kinetics.

The rates of hydrogen-deuterium exchange in the peptide groups of the alpha and beta subunits and the alpha-beta subunit complex of proton-translocating adenosine triphosphatase from the thermophilic bacterium PS3 were examined. The exchange was found to be much slower in the isolated beta subunit than in the isolated alpha subunit. This has been taken as indicating that the structure of the beta subunit is tighter than that of the alpha subunit. Adenosine 5'-triphosphate (ATP) caused tightening of a relatively tight portion of the alpha subunit and of a relatively loose portion of the beta subunit. When the alpha and beta subunits are brought into contact, tightening of the alpha subunit, but not the beta subunit, occurs. The effect of ATP on the structure of the beta subunit is more pronounced in the presence of the alpha subunit than in its absence. These findings support the idea proposed previously that the alpha subunit has an allosteric site and the beta subunit a catalytic site and that the conformation of the beta subunit is controlled by the alpha subunit.

Adenosine Triphosphatases↗

PubMed1979

Mg2+-dependent adenosine triphosphatase as an enzyme histochemical marker for the lymphomas of B-cell origin.

Twenty-nine cases of malignant lymphoma were studied by the enzyme histochemical method and membrane surface markers. Strong adenosine triphosphatase (ATPase) activity was demonstrated in 15 cases of 20 B lymphomas and in one case of null-cell lymphoma (1/1) by a light- and electron-microscopic enzyme histochemical method according to Wachstein et al. Neoplastic cells in nodules of 2 nodular lymphomas (0/2) and in 8 cases of T lymphomas (0/8) did not show any ATPase activity enzyme-histochemically. The ATPase activity of B lymphomas was electron-microscopically demonstrated on the plasma membrane of lymphoma cells but not in the cytoplasmic organelles. The specificity of ATPase activity in B lymphomas was also examined enzyme-histochemically with reference to normal lymphoid tissues. Such specificity was similar to that of non-neoplastic B lymphocytes of primary follicles and the mantle zone of secondary follicles in lymphoid tissues. Therefore, ATPase is one of the useful enzyme histochemical markers in differentiating T and B subclasses of malignant lymphomas.

Adenosine Triphosphatases↗

PubMed1977

Mitochondrial adenosine triphosphatase of the fission yeast, Schizosaccharomyces pombe 972h-. Changes in activity and oligomycin-sensitivity during the cell cycle of catabolite-repressed and -de-repressed cells.

1. Changes in activity of ATPase (adenosine triphosphatase) during the cell cycle of Schizosaccharomyces pombe were analysed in cell-free extracts of cells harvested from different stages of growth of synchronous cultures and also after cell-cycle fractionation. 2. Oligomycin-sensitive ATPase oscillates in both glucose-repressed synchronous cultures and shows four maxima of activity approximately equally spaced through the cell cycle. The amplitude of the oscillations accounts for between 13 and 80% of the total activity at different times in the cell cycle. 3. Oligomycin sensitivity varies over a fourfold range at different stages of the cell cycle. 4. The periodicity of maximum oligomycin sensitivity is one-quarter of a cell cycle. 5. These results were confirmed for the first three-quarters of the cell cycle by cell-cycle fractionation. 6. In cells growing synchronously with glycerol, ATPase activity increases in a stepwise pattern, with two steps per cell cycle; the first of these occurs at 0.54 of the cell cycle and the second at 0.95. 7. These results are discussed in relation to previously obtained data on the development of mitochondrial activities during the cell cycle.

Adenosine Triphosphatases↗

PubMed1988

Modulation of the activity of hepatic gamma-glutamyl transpeptidase, adenosine triphosphatase, placental glutathione S-transferase and adenylate cyclase by acute administration of lead nitrate.

The effect of a single administration of lead nitrate on the activity of gamma-glutamyltranspeptidase (gamma-GT), adenosine triphosphatase (ATPase), the placental form of glutathione S-transferase (GST-P) and adenylate cyclase (AC), four enzymes widely used as phenotypic markers for preneoplasia, was investigated in the liver of male Wistar rats. The results of the histochemical enzymatic staining indicated that an acute treatment with lead nitrate induces the activity of gamma-GT, mainly in the hepatocytes located around zone I of the liver acinus, with a maximum seen between 72-96 hours. On the other hand, the activity of ATPase was found to be severely inhibited at 2-3 days after treatment, as shown by a strong decrease in the staining of the bile canaliculi of zones II and III. Immunohistochemical analysis revealed that lead nitrate administration also resulted in the appearance in most of the hepatocytes of GST-P, an enzyme whose activity is almost undetectable in normal rat liver, but is elevated in preneoplastic liver lesions. Finally, lead nitrate treatment resulted in an inhibition of AC activity which was maximal after 24 hours.

Adenosine Triphosphatases↗

PubMed1977

Kinetic properties of a magnesium ion- and calcium ion-stimulated adenosine triphosphatase from the outer-membrane fraction of rat spleen mitochondria.

1. Isolated outer membranes from rat spleen mitochondria can be stored in liquid N(2) for several weeks without significant loss of ATPase (adenosine triphosphatase) activity. 2. The ATPase reaction has a broad pH optimum centering on neutral pH, with little significant activity above pH9.0 or below pH5.5. 3. A sigmoidal response of the ATPase activity to temperature is observed between 0 and 55 degrees C, with complete inactivation at 60 degrees C. The Arrhenius plot shows that the activation energy above the transition temperature (22 degrees C) (E(a)=144kJ/mol) is one-third of that calculated for below the transition temperature (E'(a)=408kJ/mol). 4. The outer-membrane ATPase (K(m) for MgATP=50mum) is inactive unless Mg(2+) is added, whereas the inner-membrane ATPase (K(m) for ATP=11mum) is active without added Mg(2+) unless the mitochondria have been depleted of all endogenous Mg(2+) (by using ionophore A23187). 5. The substrate for the outer-membrane ATPase is a bivalent metal ion-nucleoside triphosphate complex in which Mg(2+) (K(m)=50mum) can be replaced effectively by Ca(2+) (K(m)=6.7mum) or Mn(2+), and ATP by ITP. Cu(2+), Co(2+), Sr(2+), Ba(2+), Ni(2+), Cd(2+) and Zn(2+) support very little ATP hydrolysis. 6. Univalent metal ions (Na(+), K(+), Rb(+), Cs(+) and NH(4) (+), but not Li(+)) stimulate the MgATPase activity (<10%) at low concentrations (50mm), but, except for K(+), are slightly inhibitory (20-30%) at higher concentrations (500mm). 7. The Mg(2+)-stimulated ATPase activity is significantly inhibited by Cu(2+) (K(i)=90mum), Ni(2+) (K(i)=510mum), Zn(2+) (K(i)=680mum) and Co(2+) (K(i)=1020mum), but not by Mg(2+), Ca(2+), Ba(2+) or Sr(2+). 8. The outer-membrane ATPase is insensitive to the inhibitors oligomycin, NN'-dicyclohexylcarbodiimide, NaN(3), ouabain and thiol-specific reagents. A significant inhibition is observed at high concentrations of AgNO(3) (0.5mm) and NaF (10mm). 9. The activity towards MgATP is competitively inhibited by the product MgADP (K(i)=0.7mm) but not by the second product P(i) or by 5'-AMP.

Adenosine Triphosphatases↗

PubMed1977

5-bromo-2'-deoxyuridine-stimulated calcium ion- or magnesium ion-dependent ecto-(adenosine triphosphatase) activity of cultured hamster cardiac cells.

1. Treatment of hamster heart cells in primary culture with 5-bromo-2'-deoxyuridine resulted in the greatly increased activity of a particulate Ca2+- or Mg2+-dependent ATPase (adenosine triphosphatase). 2. 5-Bromo-2'-deoxyuridine exerted these effects only when it was incorporated into cellular DNA, and then in a concentration-dependent manner. 3. Serially replated cells contained less of the activity (expressed as a function of total cell protein) than did the primary cultures, but the stimulation caused by 5-bromo-2'-deoxyuridine addition was much greater. 4. The affected enzyme was apparently localized in the plasma membrane of the cells with its active centre exposed to the outer environment [ecto-(ATPase) dependent on Ca2+ or Mg2+].5. The activity was unaffected by treatment with p-chloromercuriphenylsulphonate, ouabain andverapamil. 6. Ecto (5'-nucleotidase) activity was not increased by 5-bromo-2'-deoxyuridine treatment of cells, and ecto-(p-nitrophenyl phosphatase) activity was only slightly enhanced.

Adenosine Triphosphatases↗