Effects of sodium loading and depletion in normotensive first-degree relatives of essential hypertensives.

To examine potential mechanisms responsible for the greater prevalence of hypertension among relatives of hypertensives than among relatives of normotensives, we subjected 43 normotensive first-degree relatives of known essential hypertensives and 43 age-, race-, and sex-matched normal subjects with no family history of hypertension to sodium loading and depletion. The data show that the relatives had higher blood pressures than did controls. They also had higher PRA values before and after a 2 L intravenous saline infusion over 4 hr. In addition, the relatives excreted less (p less than 0.05) sodium on the day of the infusion than did the controls. PA values and UNe excretion in the two groups did not differ. In the relatives, age correlated with systolic and diastolic blood pressure. Age correlated inversely with the 24 h urine sodium excretion on the sodium loading day. These correlations were not observed in controls. Normotensive first-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.