Salt sensitivity in normotensives with and salt resistance in normotensives without heredity of hypertension.

We have studied blood pressure responses to moderate sodium restriction from 200 to 50 mmol/day over 2 weeks in 62 normotensive subjects with and without a family history of hypertension by continuous automatic blood pressure recording. Based on the average of the blood pressure of 1 hour continuous monitoring under basal conditions, we have been able to demonstrate a significant fall of blood pressure in 28 young subjects with a heredity of hypertension after moderate sodium restriction from 200 to 50 mmol over 2 weeks (fall in systolic blood pressure 5.4 +/- 1.1, diastolic 2.5 +/- 0.8, mean blood pressure 2.9 +/- 0.7 mmHg, mean +/- SEM), whereas blood pressure remained unchanged in a group of 34 subjects without heredity of hypertension after moderate sodium restriction (change in systolic blood pressure -1.0 +/- 0.6, diastolic blood pressure -0.6 +/- 0.7 and mean blood pressure -0.93 +/- 0.67 mmHg). 29 of the subjects were studied a third time 2 weeks after having returned to their usual high sodium diet and in those in whom a blood pressure fall was observed during sodium restriction it returned to pre-intervention values. This demonstrates that normotensives with a heredity of hypertension are salt sensitive and adds further evidence that a high sodium intake may be of critical importance for the initiation of essential hypertension.