[Effect of pH on ATPase activity and 18-O metabolism catalyzed by membrane preparations of Na,K-ATPase from guinea pig kidneys].

The effect of pH in the incubation medium on ATPase activity and the direct 18O-exchange, catalyzed by initial and treated by surface active agents membrane preparations of Na, K-ATPase has been studied. The pH dependence of the ratio between the direct 18O exchange and Na,K-ATPase activity was detected; this ratio being equal to 4,5 +/- +/- 0.6, 1.5 +/- 0.1 and 0.4 +/- 0.1 at the pH values of 6.1, 7.5 and 9.0, respectively. The pretreatment of preparations by DOC or histone H2a, used in both activatory and inhibitory-amounts, abolished the effect of acid pH and made the ratio practically the same at 6.1 and 7.5 pH values. Both agents did not affect the action of the alcaline pH value equal to 9.0. Triton X-100 was not able to change the pH dependence of the ratio.