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

Studies conducted into the activity of adenosine triphosphatase (ATPase) in homogenate of several tissues of sheep and against the background of pH 7.5 (tris-HCl buffer) have shown highest enzyme activity to develop in renal cortex and cerebral cortex followed, in declining order of quotation, by liver, myocardium, and mucous membrane of small intestine. ATPase activities were studied also in the presence of pH-values between 7.2 and 8.95 (tris-HCl buffer) and between 8.6 and 11 (piperazine buffer), with the pH optimum of ATPase in the above tissues having been found to lie at approximately 9.0. Different concentrations of Mg ions were added, and maximum ATPase activity of 2 mMol ATP was obtained by adding 2 mMol Mg. Decline in ATPase activity should be expected in the case of hypomagnesaemia. Addition of different concentrations of sodium and potassium ions gave in most of the tissues tested maximum activity in response to 10 mMol potassium and 68 mMol sodium. Na-K ATPase could be inhibited by oubain particularly in cerebral and renal cortex.
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PMID:[Activities and properties of adenosine triphosphatase (ATPase) in homogenates of renal cortex, liver, myocardium and small-intestine mucosa in sheep]. 13 80

1. Explants of mammary tissue from pseudopregnant rabbits were cultured at 37 degrees C in air for 24-48h in Medium 199 buffered with 20mm-Hepes [4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid]. The medium contained insulin and corticosterone, or insulin, corticosterone and sheep prolactin in the presence or absence of ouabain, an inhibitor of Na(+)/K(+)-dependent adenosine triphosphatase. The responses of explants were assessed histologically, by measuring the tissue concentration of K(+), and by rates of synthesis of RNA, protein and fatty acids. The effect of ouabain on Na(+) and K(+) concentrations in slices of lactating rabbit mammary-gland tissue incubated for 1h at 37 degrees C in Krebs bicarbonate buffer was also studied. 2. Prolactin increased the concentration of K(+) in mammary explants, an effect prevented by ouabain. In slices of lactating tissue, there was a linear relationship between the log dose of ouabain (from 0.1 to 10mum) and increased Na(+) and decreased K(+) concentrations in the tissue. 3. Ouabain at concentrations up to 1mum did not affect the rate of synthesis of RNA, protein or fatty acids by explants cultured with insulin and corticosterone. By contrast, the stimulatory effect of prolactin on protein synthesis was diminished and the induction of medium-chain fatty acid synthesis by prolactin was almost abolished. RNA synthesis was unaffected. Histological examination showed no tissue damage by 1mum-ouabain. 4. Explants cultured in the presence of 2mum-ouabain for 24h retained their ability to respond to prolactin when the ouabain was removed from the culture medium. Between 24 and 48h they showed responses to prolactin of a magnitude similar to those of explants never exposed to ouabain. 5. These results show that a fully functional Na(+)/K(+)-dependent adenosine triphosphatase system is necessary for prolactin to promote secretory activity in rabbit mammary gland.
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PMID:Inhibition by low concentrations of ouabain of prolactin-induced lactogenesis in rabbit mammary-gland explants. 56 78