Intra-erythrocytic sodium content in normotensive offspring of normotensive and hypertensive subjects: an epidemiological study.

ABSTRACT

An increase in intra-erythrocytic sodium (IENa) content has been proposed as a genetic marker of essential hypertension. Intra-erythrocytic sodium was studied using hypotonic lysis and flame photometry after four washings with isotonic MgCl2 in 240 normotensive subjects (aged 10-45 years) on a free diet with (F+, 121 patients) or without (F-, 119 patients) hypertensive parents, recruited from a random sample of the general population. Systolic blood pressure was significantly higher in males F+ than in males F- (130 +/- 2 versus 125 +/- 2 mmHg, mean +/- s.e.m., P < 0.05), while IENa did not differ. In contrast, intra-erythrocytic potassium content (IEK) was significantly lower and red cell sodium potassium (NaK) ratio significantly higher in F+ than F-. This might reflect decreased NaK pump activity, or increased membrane permeability to cations which causes increased K leakage. No differences in blood pressure, IENa or IEK showed in female F+ versus F-. It is concluded that IENa is not a genetic marker of hypertension, and that it is probably influenced by exogenous factors. Being associated with differences in blood pressure, the abnormalities of IEK and NaK ratio might be pathogenetically linked to an early increase in blood pressure.