"Salt sensitivity' of normotensives: interactions between changes in red blood cell 22Na efflux rate constant, dietary sodium intake and changes in blood pressure.

Abstract

1. In normotensive people who altered dietary sodium intake there was no overall difference in blood pressure or efflux rate constant when on a low or high sodium intake. 2. Many individuals studied had changes in blood pressure or efflux rate constant greater than the expected variation. 3. Subjects were classified into three groups depending on the change in efflux rate constant. Seven subjects who had a fall in the efflux rate constant greater than 0.02 h when they changed from a low to a high sodium intake had a significant rise in diastolic blood pressure (73, s.e.m. = 4; to 80, s.e.m. = 3 mmHg). 4. Eight subjects who had a rise in the efflux rate constant greater than 0.02 h when they changed from a low to a high sodium intake had a significant fall in diastolic pressure (82, s.e.m. = 4; to 76, s.e.m. = 4 mmHg). 5. Eight subjects who had no change in efflux rate constant when they changed from a low to a high sodium intake had no significant change in blood pressure. 6. The above associations were found when the red blood cells were incubated in plasma. No association was found when the cells were incubated in artificial medium. 7. The data supports the hypothesis that changes in membrane Na transport have a role in the control of blood pressure. 8. It is postulated that normotensive subjects who had a decreased efflux rate constant when exposed to a high sodium intake may develop essential hypertension.