Sodium and noradrenaline effluxes from platelets in male relatives to hypertensive individuals.

The efflux rate constants for noradrenaline efflux and 22Na-efflux from platelets, the number of ouabain binding sites on platelets and the influence of plasma on ouabain binding to platelets were determined in 35 normotensive men belonging to families with a high incidence of essential hypertension and 31 men from families, where no hypertension was registered in the close relatives. The earlier finding of a higher efflux rate constant for noradrenaline in relatives was confirmed. There was a significant negative correlation between the total 22Na-efflux rate constant and the noradrenaline rate constant in relatives as well as between the number of ouabain binding sites and the noradrenaline rate constant. No such correlations were registered in the controls. The ouabain resistant 22Na-efflux rate constant was lower in relatives, but the ouabain sensitive 22Na-efflux rate constant did not differ between the groups, nor did the total number of ouabain binding sites on platelets. Number of ouabain-binding sites measured at a low concentration of (3H)-ouabain in the presence of deproteinized plasma samples was the same in both groups, contradicting the presence of an endogenous ouabain-like plasma factor in the relatives.