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At least 127 records · Page 7Linked to original sources
PubMed1984

Effect of ethanol tolerance on norepinephrine-ethanol inhibition of (Na+ + K+)-adenosine triphosphatase in various regions of rat brain.

Brain (Na+ + K+)-adenosine triphosphatase activity from untreated rats was inhibited by a combination of 1 microM norepinephrine + 50 mM ethanol (NE + EtOH), in preparations from cerebral cortex (CX), cerebellum (CB), hippocampus (HC), hypothalamus (HT), thalamus-midbrain and pons-medulla, but not from striatum. The rank order of inhibition in these regions was more similar to that of alpha-1 receptor density than of regional NE content. EtOH administration for 3 weeks produced tolerance to the hypothermic effect of EtOH; increased basal adenosine triphosphatase activity in CX, CB and HC, as measured 24 hr after withdrawal; and decreased the inhibitory effect of NE + EtOH in CX, HT, HC and CB preparations. Tolerance to the inhibitory effects of high concentrations (0.22 or 0.44 M) of EtOH alone was found only in CX, HT and HC preparations. Tolerance to NE + EtOH or to EtOH alone was greatest in HC and CX, intermediate in HT and CB and least or absent in other regions. Temperature-dependence of (Na+ + K+)-adenosine triphosphatase activity was studied in preparations from CX (high initial sensitivity to NE + EtOH, high tolerance development), CB (intermediate initial sensitivity, intermediate tolerance) and striatum (no initial sensitivity, no tolerance). Arrhenius plots showed differences between these regions, with respect to changes in transition temperature and activation energy after chronic EtOH treatment in vivo. These changes did not explain the regional differences in tolerance development. Therefore it seems unlikely that a single mechanism, such as "stiffening" of the cell membrane, can explain the varied pattern of tolerance development in different brain regions.

Animals↗
PubMed1993

Adenosine triphosphate-lead histochemical reactions in ependymal epithelia of murine brains do not represent calcium transport adenosine triphosphatase.

The strong enzyme histochemical reactions for adenosine triphosphatase (ATPase) seen in ependymal tanycytes after incubation in calcium-containing media have previously been reported as calcium transport ATPase. Investigation of these reactions showed that: (1) any nucleoside triphosphate can serve as a substrate; (2) diphosphates and monophosphates cannot replace triphosphates; this includes p-nitrophenyl phosphate which is readily hydrolysed by plasma membrane transport ATPases; (3) strong localization occurs in the presence of millimolar concentrations of either calcium or magnesium ions; there is no absolute requirement for calcium ions; (4) they are not inhibited by sulphydryl inhibitors or calmodulin antagonists; (5) lead phosphate precipitates are localized almost entirely on the external face of tanycyte plasma membranes. In addition, the technique gives strong localization to vessels in the choroid plexus but not to the choroidal epithelium. Immunohistochemistry with a primary antibody raised against Ca2+, Mg2(+)-ATPase stains the choroidal epithelium but not the vessels or the ependymal tanycytes. These results are inconsistent with identification of the reaction as calcium transport ATPase but support characterization as an ecto-ATPase.

Adenosine Triphosphatases↗
PubMed1994

Preeclampsia and calcium adenosine triphosphatase activity of red blood cell ghosts.

OBJECTIVE: The current work was undertaken to study the calcium adenosine triphosphatase activity of red blood cell membranes from pregnant women with preeclampsia. STUDY DESIGN: Six normotensive and six preeclamptic pregnant women at 38 to 39 weeks of gestation were studied. The diagnosis of preeclampsia was made on the basis of blood pressure (> 140/90 mm Hg), proteinuria (> 0.5 gm of urinary protein per day), or edema. Hemoglobin-free red blood cell ghosts were prepared from the heparinized blood samples and were used to determine the calcium adenosine triphosphatase activity. RESULTS: It was found that the calcium adenosine triphosphatase activity of preeclamptic women is diminished by about 50% compared with that of normotensive pregnant women. CONCLUSION: A diminution of the calcium adenosine triphosphatase activity of erythrocytes in preeclampsia might be an indication that the in vivo activity of the calcium pump of these cells is diminished, which could, in turn, drive the cells to increase their cytoplasmic free calcium concentration.

Adult↗
PubMed1968

Tritiated digoxin binding to (Na+ + K+)-activated adenosine triphosphatase: possible allosteric site.

Tritiated H(3)-digoxin specifically binds to a cardiac (Na(+) + K(+))-activated adenosine triphosphatase. In the presence of adenosine triphosphate and other nucleoside di- and triphosphates, binding is stimulated by sodium ion, the apparent rate constant being similar to that reported for phosphorus-32 incorporation from adenosine triphosphate and for the adenosine triphosphatase activity. In the presence of magnesium, manganese, inorganic phosphate, or other ions, sodium ion inhibits binding. The data support an allosteric type of sodium-potassium ion pump.

Adenosine Triphosphatases↗
PubMed1979

Adenosine triphosphatase of mycobacteria.

A Mg+2-(Ca+2)-activated adenosine triphosphatase activity has been demonstrated in saprophytic, human pathogenic and non-pathogenic, and atypical, species of mycobacteria. (Na+ + K+)-activated adenosine triphosphatase was absent in the species investigated. The effect of age of culture on enzyme activity was revealed in an increase up to mid logarithmic phase of growth, and a decline thereafter. Differences in oxygen tensin during growth did not alter enzyme activity. Isonicotinic acid hydrazide and streptomycin inhibited the enzyme activity.

Adenosine Triphosphatases↗
PubMed1982

Effect of indomethacin on Ca2+-stimulated adenosine triphosphatase in the synaptic vesicles of rat brain in vitro.

1. Indomethacin inhibits calcium-stimulated adenosine triphosphatase (Ca2+-ATPase), calcium, magnesium-stimulated adenosine triphosphatase (Ca2+,Mg2+-ATPase) and magnesium-stimulated adenosine triphosphatase (Mg2+-ATPase) activities in rat brain synaptic vesicles in vitro. 2. The Ca2+-ATPase activity is most strongly affected by this drug all of the activities of ATPases tested. 3. The decrease of Ca2+-ATPase activity by addition of indomethacin is due to a decrease of Vmax. 4. The Ki values for this drug for ATP and Ca2+ in Ca2+-ATPase were 1.13 mM and 0.68 mM, respectively.

Adenosine Triphosphate↗
PubMed1974

The magnesium ion-dependent adenosine triphosphatase of myosin. Two-step processes of adenosine triphosphate association and adenosine diphosphate dissociation.

The kinetics of protein-fluorescence change when rabbit skeletal myosin subfragment 1 is mixed with ATP or adenosine 5'-(3-thiotriphosphate) in the presence of Mg(2+) are incompatible with a simple bimolecular association process. A substrate-induced conformation change with DeltaG(0)<-24kJ.mol(-1) (i.e. DeltaG(0) could be more negative) at pH8 and 21 degrees C is proposed as the additional step in the binding of ATP. The postulated binding mechanism is M+ATPright harpoon over left harpoonM.ATPright harpoon over left harpoonM*.ATP, where the association constant for the first step, K(1), is 4.5x10(3)m(-1) at I 0.14m and the rate of isomerization is 400s(-1). In the presence of Mg(2+), ADP binds in a similar fashion to ATP, the rate of the conformation change also being 400s(-1), but with DeltaG(0) for that process being -14kJ.mol(-1). The effect of increasing ionic strength is to decrease K(1), the kinetics of the conformation change being essentially unaltered. Alternative schemes involving a two-step binding process for ATP to subfragment 1 are possible. These are not excluded by the experimental results, although they are perhaps less likely because they imply uncharacteristically slow bimolecular association rate constants.

Adenosine Diphosphate↗
PubMed1996

Modulation of histamine release by sodium, potassium adenosine triphosphatase inhibition.

BACKGROUND: Previous studies have shown that a sodium, potassium adenosine triphosphatase inhibitor is present in the plasma of allergic subjects in whom enhanced histamine releasability has also been reported. PURPOSE: The purpose of this study was to determine the effect of in vitro sodium, potassium adenosine triphosphatase inhibition on whole blood histamine release. METHODS: Samples obtained from 12 patients with allergic rhinitis and 12 nonallergic subjects were incubated in duplicate for 30 minutes with anti-IgE antibody (100 micrograms/mL) or control buffer following a 0-, 10-, 20-, 30-, 60-, 120- and 180-minute preincubation with ouabain (3.0 mM) or diluent. Cell supernatants were assayed for histamine by radioimmunoassay and results were expressed as a percentage of total histamine release. RESULTS: Mean (+/- 1 SEM) anti-IgE induced release, in the presence and absence of ouabain, respectively, for allergic subjects was 27.5 +/- 5.5 and 21.0 +/- 4.5 (ten minutes, P < 0.05), 30.3 +/- 6.0 and 22.4 +/- 4.8 (20 minutes, P < .025), 28.9 +/- 5.2 and 23.5 +/- 4.1 (30 minutes), 33.8 +/- 7.1 and 26.7 +/- 5.4 (60 minutes, P < .05), 43.2 +/- 7.5 and 24.3 +/- 4.6 (120 minutes, P < .001), and 34.5 +/- 5.0 and 29.8 +/- 5.4% (180 minutes). Spontaneous histamine release in allergic subjects was also significantly increased by ouabain. Mean (+/- SEM) spontaneous release, in the presence and absence of ouabain, respectively, for allergic subjects was 2.0 +/- 0.5 and 0.9 +/- 0.2 (60 minutes, P < .025), 2.8 +/- 0.5 and 1.9 +/- 0.4 (120 minutes, P < .05), and 5.4 +/- 1.5 and 3.9 +/- 0.8% (180 minutes, P < .005). Ouabain did not significantly alter histamine release in non-allergic subjects. CONCLUSIONS: These data show that ouabain induced a significant increase in both spontaneous and induced histamine release in allergic subjects. In vivo, sodium, potassium adenosine triphosphatase inhibition may have an effect on histamine release in allergic subjects.

Adult↗
PubMed1989

Decreased adenosine triphosphatase activity in the absence of adrenocorticosteroids.

Changes in adenosine triphosphatase activity and cellular integrity of rat inner-ear tissues were observed after removal of adrenal steroids via bilateral adrenalectomy. Statistical significance of total and magnesium ion-dependent adenosine triphosphatase activities of the stria vascularis, spiral ligament, and ampullar dark cells from adrenalectomized animals was detected when compared with those of controls as demonstrated by fluorometric microassay. Although there was a similar reduction of activity in utricular dark-cell tissues, no significant difference between the treated and control animals was observed. An increase of intercellular space and a decrease in basolateral infoldings of cells of the stria vascularis and dark cell regions of adrenalectomized animals were observed. Such data collectively provide indirect evidence that adrenal steroids are involved in the cellular regulation of inner-ear tissues that are concerned with fluid and ionic microhomeostasis.

Adenosine Triphosphatases↗
PubMed1977

A simple procedure for isolating adenosine triphosphatase from mitochondria.

A simple method for isolation of adenosine triphosphatase (EC 3.6.1.3) from mitochondria is described. The enzyme is released from mitochondrial Lubrol particles by drastic sonication and purified by gel filtration on Sepharose 6-B. The described procedure is effective in isolating adenosine triphosphatase from rat liver as it is from beef heart mitochondria. The enzyme isolated from beef heart has a specific activity of 120 mumol P/min per mg protein and enzyme isolated from rat liver has a specific activity of 70 mumol P/min per mg protein when measured as a release of inorganic phosphate.

Adenosine Triphosphatases↗
PubMed1976

Cytochemical localization of transport adenosine triphosphatase in the ferret placenta.

The distribution of transport adenosine triphosphatase in the ferret placenta was examined cytochemically by light and electron microscopy. The enzyme was detected in the syncytiotrophoblast but was absent from maternal tissues. It appeared to be associated with cytoplasmic processses on syncytiotrophoblast surfaces directly related to foetal or maternal capillaries. The functional significance of transport adenosine triphosphatase is discussed with reference to the transport of solutes between the maternal and foetal circulation across the trophoblast layer.

Adenosine Triphosphatases↗
PubMed1996

Changes in Na,K-adenosine triphosphatase (ATPase) concentration and Na,K-ATPase-dependent adenosine triphosphate turnover in human erythrocytes in diabetes.

The concentration of Na,K-adenosine triphosphatase (ATPase) and Na,K-ATPase-dependent adenosine triphosphate (ATP) turnover was measured in fasting blood samples of 20 subjects with insulin-dependent diabetes mellitus (IDDM), 22 subjects with non-insulin-dependent diabetes mellitus (NIDDM), and 20 nondiabetic subjects. [3H]ouabain binding was used to determine Na,K-ATPase concentration. There were 471 +/- 70 (mean +/- SD) ouabain binding sites per erythrocyte, normally distributed in the nondiabetic subjects. The number of ouabain sites per cell was lognormally distributed in the two populations of diabetic subjects. The mean of lognormal distributions of ouabain sites per cell was significantly lower in the IDDM group. The mean of the lognormal distribution for the NIDDM group was not significantly different from that of the nondiabetic subjects. Na,K-ATPase-dependent ATP turnover (molar activity) was 9,580 +/- 742 mol/mol minute (mean +/- SD) normally distributed in the nondiabetic population. A lognormal distribution was observed in the diabetic population. Means of the lognormal distributions were significantly different: 3.98 +/- 0.05 for the nondiabetic population and 3.13 +/- 0.48 for both diabetic populations. Changes in the concentration of Na,K-ATPase (ouabain sites per cell) and Na,K-ATPase-dependent ATP turnover did not correlate with hemoglobin A1C (HbA1C) or with blood glucose. This would suggest that elevated glucose concentrations do not directly cause decreased Na,K-ATPase function in the diabetic erythrocyte.

Adenosine Triphosphate↗
PubMed1981

Cardiac sodium, potassium-adenosine triphosphatase as a possible site of adriamycin-induced cardiotoxicity.

Adriamycin ws tested as a possible inhibitor of cardiac sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase). At concentrations of 10(-4) M and lower, Adriamycin had no effect upon either ouabain-sensitive (Na-K-ATPase) or ouabain-insensitive adenosine triphosphatase activity in homogenates and microsomal fractions of cardiac tissue from several different species. Adriamycin inhibited adenosine triphosphatase activity at a concentration of 10(-3) M, but this was due to the inhibition of ouabain-insensitive adenosine triphosphatase rather than to inhibition of Na-K-ATPase. Under no condition was an inhibition of Na-K-ATPase activity by Adriamycin observed. These conditions included preincubation of the enzyme with Adriamycin, chelation of Ca2+, addition of reduced nicotinamide adenine dinucleotide phosphate, and variation of buffer and pH. It was concluded that Na-K-ATPase is not a likely site of Adriamycin-induced cardiotoxicity.

Adenosine Triphosphatases↗
PubMed1972

Adenosine triphosphatase of bean plastids: its properties and site of formation.

Extracts of bean (Phaseolus vulgaris L.) etioplasts and chloroplasts contain a dithiothreitol-activated Ca(2+)-dependent adenosine triphosphatase which is inhibited by Dio-9. The chloroplast and etioplast enzymes have identical R(F) values upon disc gel electrophoresis. Optimum extraction of the enzyme from either plastid preparation is accomplished with 1 mm ethylenediamine tetraacetic acid. Photophosphorylation capacity can be partially restored to depleted chloroplast preparations by addition of either the chloroplast or etioplast extract. These results suggest that the adenosine triphosphatase from etioplasts and chloroplasts represents a modified coupling factor for photophosphorylation.The specific activity of the adenosine triphosphatase in the extracts of plastids increases upon greening of etiolated plants due to protein synthesis. This light-induced increase is inhibited by both chloramphenicol and cycloheximide, specific inhibitors of chloroplastic and cytoplasmic protein synthesis. There is no accumulation of adenosine triphosphatase in postribosomal supernatants of cycloheximide or chloramphenicol treated leaves. The results indicate that both the chloroplastic and the cytoplasmic ribosomal systems are required for the formation of the chloroplast adenosine triphosphatase.

Journal Article↗
PubMed1983

Purification and characterization of the soluble form of mitochondrial adenosine triphosphatase from sweet potato.

The soluble form of mitochondrial adenosine triphosphatase was purified in an electrophoretically and immunologically pure form from sweet potato root tissue. The enzyme consisted of six kinds of subunits with different molecular weights (52,500, 51,500, 35,500, 26,000, 23,000, and 12,000), and its molecular weight was about 370,000. Adenosine triphosphatase associated with the submitochondrial particles was oligomycin-sensitive and heat-labile, whereas the soluble form of the enzyme was oligomycin-insensitive and cold-labile. The enzyme in either the membrane-bound or the soluble form showed negative cooperativity. Both experiments with polyacrylamide gel electrophoresis and immunological methods suggest that some of the subunits, probably those with molecular weights of 52,500 and 51,500, are dissociated from the enzyme protein during storage of the enzyme preparations.

Adenosine Triphosphatases↗