Sodium and potassium status, plasma renin and aldosterone profiles in normotensive and hypertensive Johannesburg blacks.

Many studies have suggested that there is an association between the sodium status, plasma renin and aldosterone profile and essential hypertension. We measured serum, urine and red blood cell (RBC) sodium and potassium, plasma renin and aldosterone levels in normotensive Whites, normotensive Blacks, mildly hypertensive Blacks, severely hypertensive Blacks and Blacks with malignant hypertension. There were no important differences between the groups studied as regarded the serum sodium, serum potassium and urinary sodium excretion values. However, the urinary potassium excretion was significantly lower in normotensive and hypertensive Blacks than in Whites. RBC sodium concentrations showed no significant differences in the mean values across the range of degrees of hypertension in Blacks, although they tended to be higher in the more severely hypertensive groups. Blacks with mild-to-moderate hypertension as well as the severely hypertensive group had significantly lower plasma renin levels than the normotensive group; only in the malignant hypertensives with advanced renal failure did the plasma renin and aldosterone levels rise.