Erythrocyte membrane ouabain-sensitive Na+, K+ - ATPase of hypertensive Nigerians

Abstract

An assessment of the ATPase functions of erythrocyte membrane of newly identified subjects having essential hypertension shows that Na +, K+ -ATPase activity is higher in normal membranes than in membranes of individuals with essential hypertension. A study of the dependence of the enzyme on ATP in the presence of non-limiting concentrations of Na+ (120 mM) and Mg2 + (3 mM) shows that the pump in the membranes of hypertensive individuals, like that of normal humans, is easily saturable by ATP (≥2 µM). Analysis of the results of kinetic studies on the enzyme, in the presence of 5 mM K+, using the Hanes plot, reveals that, although the affinity (Km) of the pump for ATP is unaffected in essential hypertension, its maximum velocity (V max) is lower than in normal membranes. Even though the reason for a reduced-sodium pump function in essential hypertension is not yet clear, it may not be unconnected with the presence of an endogenous inhibitor or with genetic or diet-induced membrane defects, as previously proposed by other workers in this area of research.