An approach to the evaluation of genetic influences on factors that regulate arterial blood pressure in man.

To assess the influence of heredity on factors that help regulate the arterial blood pressure in man, we conducted sodium-loading and depletion studies in monozygotic and dizygotic twins, normotensive first-degree relatives of essential hypertensives, and in normotensive control subjects matched for age, sex, and race. Following sodium-loading, we found evidence for the influence of genetic variance on the natriuretic responses, plasma renin activity (PRA), plasma aldosterone concentrations (PA), and plasma and urinary norepinephrine. Relatives of hypertensives differed from controls in that they had higher blood pressures, greater renin values, and relatively sluggish natriuretic responses. Since renin and fractional sodium excretion values were inversely correlated in all subject groups, it is possible that the heritable influences we observed on sodium excretion were mediated by the renin-angiotensin-aldosterone system.