The Stimulating Effect of Angiotensin and Vasopressin on Adenosine Triphosphatase Activity in vitro

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Abstract
Levin, K.The stimulating effect of angiotensin and vasopressin on adenosine triphosphatase actiuity in vitro. Acta physiol. scand. 1970.79. 37–49.The effect of angiotensin on the levels of ATPase activity in homogenates of rat kidney cortex and other tissues has been studied. With the addition of 1.7 μg of angiotensin per ml of incubation medium containing in addition 4 mM ATP, Mg++, Na+, K+, EDTA and imidazole buffer pH 7.2, a stimulation of 8.6 ± 0.5 % of the ATPase activtiy was observed. The presence of Mg++and Na+was found to be necessary for the demonstration of angiotensin stimulation. The optimal pH for the effect of angiotensin was found to be 7.2 and this was confined to very narrow limits. The degree of stimulation was greatest in fresh homogenates and this rapidly decreased on storage. Centrifugation of the homogenates indicated that the ATPase activtiy which could be stimulated by angiotensin was particle bound. A similar effect to the one produced by angiontensin was obtained with vasopressin though not with oxytocin or a number of other vasoactive substances known to effect the renal handling of sodium ions. Stimdation by angiotensin could be demonstrated in kidney cortex from mouse, guinea pig, rabbit, rat and from man, and in homogenates from a number of other tissues. It was concluded that the stimulation of ATPase by angiotensin was brought about through the same mechanisms as the stimulation produced by ouabain, and that both these phenomena are closely related to Na+‐K+ATPase. The possible physiological significance of these findings is discussed.