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

Transport properties of membrane vesicles isolated from two adenosine triphosphatase-deficient mutants of Escherichia coli, NR70 and DL54, were compared with those of vesicles prepared from the corresponding parental strains. As reported previously (Rosen, 1973; Altendorf et al., 1974), vesicles prepared from these mutants grown under aerobic conditions exhibited defective amino acid transport, and activity was restored after treatment with dicyclohexylcarbodiimide. In sharp contrast, however, vesicles isolated from the same mutants grown anaerobically in the presence of nitrate exhibited completely normal transport activity when assayed under either anaerobic or aerobic conditions. Suppression of the transport defect was not due to the manner by which the vesicles were prepared, and the adenosine triphosphatase deficiency was not ameliorated by anaerobic growth in the presence of nitrite. Finally, the transport activity of vesicles prepared from the mutants grown under aerobic conditions was relatively resistant to the effect of 1.0 M guanidine hydrochloride extraction, whereas the activity of vesicles prepared from mutants grown anaerobically was totally refractory to the effect of the chaotrope.
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PMID:Physiological suppression of a transport defect in Escherichia coli mutants deficient in Ca2+, Mg2+-stimulated adenosine triphosphatase. 12 84

Daily intraperitoneal administration of thorium nitrate produced progressive morphological and biochemical alterations with the increase in thorium concentration in rat testis. The degenerative changes in the seminiferous tubules increased with the duration of treatment and after 90 days calcification occurred in about 25% of the tubules and in the connective tissue of the tunica albuginea. The activity of adenosine triphosphatase and alkaline phosphatase increased markedly as a result of thorium administration. An attempt has been made to interrelate histopathological and enzymatic changes and the metal concentration in the testicular tissue.
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PMID:Thorium induced testicular changes in rats. 13 60

Dual localization of acid phosphatase in lysosomal and extralysosomal sites of the tubule epithelial cells of normal mouse kidney was observed at the light and electron microscope level using a modified Gomori lead-salt method with p-nitrophenylphosphate (pNPP) as substrate. Based on previous biochemical and cytochemical findings, we developed optimal conditions for the enzyme activity in extralysosomal sites. The conditions used for the light microscopic level consisted of 1.5 mM PNPP, 2.0 MM Pb(NO3)2 and 0.05 M acetate buffer (pH 5.8). Those for the electron microscopic study required 3.0 mM PNPP, 3.6 MM Pb(NO3)2 and 0.1 M acetate buffer (pH 5.8). This modified lead-salt technique was highly specific and provided a suitable method for the demonstration of nonlysosomal as well as lysosomal sites of acid phosphatase activity in the tubule epithelial cells of normal mouse kidney. As expected, the enzyme activity appeared in the lysosomes, but the prominent reaction in the brush border, the rough endoplasmic reticulum and basal infolding plasma membranes was not anticipated. We were able to demonstrate in situ organelle precursors of microsomal acid phosphatase such as endoplasmic reticulum, plasma membrane and basal infolding membranes showing the same substrate preference, which had been observed previously in biochemical studies in our laboratory. Since the possible participation of alkaline phosphatases, K+-pNPPase or Na+-K+-adenosine triphosphatase was ruled out by use of appropriate inhibitors, the enzyme-reactive sites can be interpreted as reflecting nonspecific acid phosphatase.
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PMID:Demonstration of lysosomal and extralysosomal sites for acid phosphatase in mouse kidney tubule cells with p-nitrophenylphosphate lead-salt technique. 23 53

Proximal convoluted tubules were dissected from rabbit kidneys and perfused in vitro in order to determine the effect of monovalent ions on fluid absorption and transepithelial voltage. Replacement of sodium in the perfusate and bath by lithium, tetramethyl ammonium or choline caused the rate of fluid absorption and voltage to fall to near zero. Replacement of potassium in the bath by sodium had the identical effect. Replacement of chloride by nitrate or perchlorate had comparatively little effect. The results are consistent with the generally held view that active sodium transport (mediated by a Na- and K- activated adenosine triphosphatase) is the primary process responsible for the absorption of the fluid and the voltage. Replacement of bicarbonate in the perfusate and bath by chloride caused the rate of fluid absorption to decrease by 33%. The possible relation between sodium transport and bicarbonate is discussed.
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PMID:Role of monovalent ions in the reabsorption of fluid by isolated perfused proximal renal tubules of the rabbit. 97 42

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

Experiments were designed to determine the efficacy of different types of liver cell proliferative stimuli given during exposure to several liver tumor-promoting regimens, on the formation of foci of enzyme-altered hepatocytes. Male Wistar rats were initiated with diethylnitrosamine (150 mg/kg body wt). After a 2 week recovery period animals were subjected to promoting regimens, the resistant hepatocyte model, the phenobarbital model and the orotic acid model. While the rats were on these regimens they were given liver cell proliferative stimulus, either a compensatory type (two-thirds partial hepatectomy or a necrogenic dose of carbon tetrachloride) or a direct hyperplastic stimulus such as that induced by the primary mitogen, lead nitrate. Initiated cells so promoted by these regimens were monitored as foci of enzyme-altered hepatocytes positive for gamma-glutamyltransferase and placental glutathione S-transferase or deficient for adenosine triphosphatase. While carbon tetrachloride and partial hepatectomy-induced compensatory regeneration stimulated the promoting ability of the regimens used, direct hyperplasia could not stimulate the formation of foci and/or nodules from initiated hepatocytes. Evaluation of thymidine incorporation indicated that there was no significant difference in the extent of DNA synthesis in both the proliferative stimuli irrespective of the promoting procedure used.
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PMID:Mitogen-induced liver hyperplasia does not substitute for compensatory regeneration during promotion of chemical hepatocarcinogenesis. 134 15

To reduce the vascular contracting effect of the cardiac glycoside, proscillaridin (1), all kinds of its nitrates were prepared by utilizing effectively an isopropylidene function as a protective group. The pharmacological activities of proscillaridin nitrates were evaluated by the use of isolated guinea-pig papillary muscle preparations and Na+,K(+)-adenosine triphosphatase preparations from the dog kidney. Furthermore, the effect for smooth muscle using the helical strips isolated from 13-week old spontaneously hypertensive rat was examined. The positive inotropic effects and Na+, K(+)-adenosine triphosphatase inhibition activities of mononitrates (6, 9, 15) and dinitrates (3, 4, 5) were a little less potent than 1, but those of trinitrate (2) were much reduced. Every nitrate did not exhibited a vascular contracting effect but a relaxing effect. Among them, the vascular relaxing effects of 2',3'-dinitrate (3) and 2',4'-dinitrate (4) were more potent than those of the other nitrates.
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PMID:[Studies on cardiac ingredients of plants. VIII. Preparation of nitrates of proscillaridin and their pharmacological activities]. 166 12

A series of experiments was performed to investigate the effect of different types of cell proliferation on the development of enzyme-altered preneoplastic hepatic foci in male Wistar rats. Animals were given a single dose of diethylnitrosamine (100 mg/kg body weight). After a 2-week recovery period liver cell proliferation was repeatedly induced by four or eight necrogenic doses of carbon tetrachloride (compensatory cell proliferation), or by four or eight treatments with three different liver mitogens, namely lead nitrate, ethylene dibromide and nafenopin (direct hyperplasia). The carcinogen altered hepatocytes were monitored as gamma-glutamyltransferase positive or adenosine triphosphatase negative foci. The results indicate that compensatory cell proliferation induced by both four and eight carbon tetrachloride treatments enhanced the growth of diethylnitrosamine-initiated hepatocytes to enzyme-altered foci. On the contrary, repeated waves of cell proliferation induced by liver mitogens did not result in any significant number of enzyme-altered foci.
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PMID:Cell proliferation and promotion of rat liver carcinogenesis: different effect of hepatic regeneration and mitogen induced hyperplasia on the development of enzyme-altered foci. 197 Jul 63

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.
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PMID:Modulation of the activity of hepatic gamma-glutamyl transpeptidase, adenosine triphosphatase, placental glutathione S-transferase and adenylate cyclase by acute administration of lead nitrate. 290 38

Thermoacidophilic archaebacteria have gained much interest because of their phylogenetic distance to eubacteria and eukaryotes and also because of their unique living conditions. Investigation of the energy-converting system therefore offers a key for understanding the evolutionary position and environmental adaptation of these unusual bacteria. A plasma-membrane-associated adenosine triphosphatase with specific activities of 0.3-0.6 mumol min-1 (mg protein)-1 has been detected in the thermoacidophilic archaebacterium Sulfolobus acidocaldarius (DSM 639). The enzyme exhibits two optima at pH 5.5 and 8.0, sulfite activation leads to only one optimum at pH 6.25. In the presence of the divalent cations Mg2+ or Mn2+ it hydrolyzes ATP with highest reactivity and also other purine and pyrimidine nucleotides, but not ADP and pyrophosphate. A specific stimulation by monovalent cations is not observed. The ATPase activity is not inhibited by N,N'-dicyclohexylcarbodiimide, azide or vanadate, but it is by the vascular ATPase inhibitor nitrate with an [I]50 of 8 mM. Linear Arrhenius plots up to 75 degrees C reflect pronounced adaptation to the hot environment of the archaebacterium. The solubilized ATPase as localized by activity staining in non-denaturating gels and further analyzed by sodium dodecyl sulfate electrophoresis is composed of two major polypeptides of 65 and 51 kDa reminiscent of the alpha and beta subunits of eubacterial and eukaryotic F0F1-ATPases. The ATPase is suggested as a probable candidate for a reversibly acting ATP synthase responsible for oxidative phosphorylation found in Sulfolobus acidocaldarius.
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PMID:A plasma-membrane associated ATPase from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius. 295 1


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