EFFECTS OF SODIUM LOADING AND DEPLETION IN NORMOTENSIVE 1ST-DEGREE RELATIVES OF ESSENTIAL HYPERTENSIVES

Abstract

To examine potential mechanisms responsible for the greater prevalence of hypertension among relatives of hypertensives than among relatives of normotensives, 43 normotensive 1st-degree relatives of known essential hypertensives and 43 age-, race- and sex-matched normal subjects with no family history of hypertension were subjected to Na loading and depletion. The data show that the relatives had higher blood pressures than did controls. They also had higher PRA [plasma renin activity] values before and after a 2 l i.v. saline infusion over 4 h. In addition, the relatives excreted less (P < 0.05) Na on the day of the infusion than did the controls. PA [plasma aldosterone] values and UNe [urinary norepinephrine] excretion in the 2 groups did not differ. In the relatives, age correlated with systolic and diastolic blood pressure. Age correlated inversely with the 24 h urine Na excretion on the Na loading day. These correlations were not observed in controls. Normotensive 1st-degree relatives of hypertensives differ from relatives of nonhypertensives in that they have higher PRA values and a blunted natriuretic response to a saline load. These features may predispose them to the development of hypertension.