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At least 559 records · Page 31Linked to original sources
PubMed1985

Sodium-potassium-adenosine triphosphatase in nephron segments of spontaneously hypertensive rats.

Sodium pump activity of blood vessels has been reported to decrease in several animal models of hypertension. We studied sodium-potassium-adenosine triphosphatase (Na-K-ATPase) activity of renal tubular segments in 12-week-old spontaneously hypertensive rats and in age-matched Wistar-Kyoto normotensive rats. The enzyme activity of the individual nephron segments was determined by a microfluorometric assay in which ATP hydrolysis is coupled with NADH oxidation. In the spontaneously hypertensive rats, systolic blood pressure was significantly higher (181 +/- 3 mm Hg) than in the Wistar-Kyoto rats (134 +/- 2 mm Hg). However, there was no difference in mean Na-K-ATPase activity in any of the nephron segments from the spontaneously hypertensive compared with the Wistar-Kyoto group. It is concluded that Na-K-ATPase activity does not change in any of the nephron segments with spontaneous hypertension.

Adenosine Triphosphatases↗
PubMedDate not supplied

Molecular properties of membrane lipids and activity of a membrane adenosine triphosphatase from Acholeplasma laidlawii B.

The effects of membrane lipid fluidity and phase state on enzyme activity were evaluated by careful analysis of Arrhenius plots of the Na+, Mg2+-dependent adenosine triphosphatase (referred to hereafter as ATPase) from Acholeplasma laidlawii B membranes and differential thermal analysis of the membrane lipid phase transitions. Arrhenius plots of the ATPase activity in membranes containing only liquid-crystalline lipids are gently curved and have the same form regardless of the membrane fatty liver composition. The absolute ATPase activity at temperatures well above the lipid phase transition temperature varies in a complex fashion with fatty acid composition. As the membrane enters its lipid phase transition, ATPase activity begins to fall off more rapidly than it does above the transition. Quantitative analysis of the results suggests that ATPase is reversibly inactivated when its vicinal lipids undergo a transition to a state of reduced plasticity at low temperatures. This transition is driven by the conversion of the bulk membrane lipid phase to the gel state, but it is less cooperative and occurs at lower temperatures than the bulk lipid transition. The results suggest that the familial "biphasic linear" Arrhenius plots reported for many membrane enzymes and transport systems may, in fact, have more complex shapes, analysis of which can furnish useful information about the behavior of the enzyme molecule or transport system in its membrane environment.

Acholeplasma laidlawii↗
PubMed1976

Comparative species studies on the effect of monovalent cations and ouabain on cardiac Na+, K+-adenosine triphosphatase and contractile force.

The effects of ouabain, Rb+ and Tl+ on Na+, K+-adenosine triphosphatase (Na+,K+-ATPase; Mg++-dependent, Na+,K+-activated ATP phosphohydrolase, EC 3.6.1.3) and contractile force were compared in guinea-pig and rat hearts. Although ouabain produced a dose-dependent positive inotropic effect in rat as well as in guinea-pig atrial preparations, concentrations of ouabain needed to produce comparable positive inotropic effects were more than an order of magnitude higher in rats than in guinea pigs. Additionally, the time to reach the plateau of the inotropic response was significantly shorter in rat than in guinea-pig atrial preparations. Concentrations of ouabain needed to produce comparable inhibition of cardiac Na+, K+-ATPase in vitro observed with partially purified cardiac enzyme preparations were also more than an order to magnitude higher in rats than in guinea pigs.

Adenosine Triphosphate↗
PubMed1990

Influence of prolactin, androgens and bromocriptine on seminal vesicular and prostatic adenosine triphosphatases in castrated adult monkeys Macaca radiata.

E ects of prolactin (PRL), bromocriptine (Br), testosterone propionate (TP), dihydrotestosterone (DHT) and the combinations of these androgens with PRL/Br on specific activities of adenosine triphosphatases (ATPases) of seminal vesicles and cranial and caudal prostates were studied in castrated adult bonnet monkeys. Castration decreased all ATPases (sodium/potassium, magnesium and calcium dependent) of seminal vesicles and both the lobes of prostate. PRL restored the normal activities of all ATPases in both the organs. Br given alone decreased all ATPases of prostate but caused no significant alteration, particularly calcium dependent ATPases of seminal vesicles and caudal prostate. TP/DHT replacement restored all ATPases of both the organs to the normal levels. PRL + TP/DHT further enhanced all the ATPases activities of all the regions studied. Br + TP/DHT decreased all ATPases but it did not produce any alteration in the calcium ATPases of seminal vesicles. The results suggest that prolactin facilitates membrane transport enzymes in the cranial and caudal prostate and seminal vesicles of adult castrated bonnet monkeys.

Adenosine Triphosphatases↗
PubMedDate not supplied

Mutation analysis of copper-transporting P-type adenosine triphosphatase (ATP7B) in human solid carcinomas.

A major obstacle in the treatment of human solid carcinomas is the intrinsic/acquired resistance to cisplatin-based chemotherapy. Copper-transporting P-type adenosine triphosphatase (ATP7B) has been reported to be associated with cisplatin resistance in vitro. ATP7B is overexpressed in human solid carcinomas such as breast, gastric and oral squamous cell carcinomas. ATP7B expression has an influential effect on some subsets of patients with cisplatin-treated carcinomas. ATP7B mutation is well-known as a cause of Wilson's disease. In addition, the six copper-binding domain and ATP-binding domain of ATP7B are important for the transportation of metals. Therefore, we performed the mutation analysis at the six copper-binding domain and ATP-binding domain of ATP7B. No mutation at the six copper-binding domain and ATP-binding domain was observed in breast, gastric and oral squameous cell carcinomas. These results indicate that the analysis of the ATP7B gene and/or protein will be helpful for the choice of chemotherapy in patients with human solid carcinomas.

Adenosine Triphosphatases↗
PubMed1997

Digoxin-like immunoreactive substance and sodium-potassium-adenosine triphosphatase inhibition in normal pregnancy: a longitudinal study.

OBJECTIVE: To measure the levels of digoxin-like immunoreactive substance and digitalis-like factor bioactivity as manifested by sodium-potassium-adenosine triphosphatase (ATPase) inhibition throughout pregnancy. METHODS: Serum samples were collected from primigravidas in early (15 +/- 1.8 weeks), mid (26 +/- 1.2 weeks), and late (36 +/- 1.1 weeks) gestation, as well as at 6 +/- 1.1 weeks postpartum (mean +/- standard error). Digoxin-like immunoreactive substance levels were determined by radioimmunoassay and digitalis-like factor bioactivity was determined by inhibition of ATPase. Data were analyzed by means of repeated measures analysis of variance. RESULTS: In 41 women with normal pregnancy outcomes, levels of digoxin-like immunoreactive substance rose progressively and significantly (P < .001) throughout pregnancy and returned to normal levels postpartum. Inhibition of ATPase activity also rose significantly (P < .004), but not as dramatically, during pregnancy and remained elevated 6 weeks postpartum. CONCLUSION: Although digoxin-like immunoreactive substance levels rise in pregnancy, functional digitalis-like factor activity, as manifested by inhibition of ATPase, does not parallel this rise strictly, implying that digoxin-like immunoreactive substance receptors may be reset during normal pregnancy. The enhanced cardiac performance that occurs in normal pregnancy may be mediated in part by increased digitalis-like factor activity.

Adenosine Triphosphatases↗