[Activities and properties of adenosine triphosphatase (ATPase) in homogenates of renal cortex, liver, myocardium and small-intestine mucosa in sheep].

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.