Racial differences in aldosterone excretion and plasma aldosterone concentrations in children.

Blacks are more likely to have hypertension, have lower levels of plasma renin activity, and typically consume less potassium than whites. Whether blacks and whites secrete different amounts of aldosterone is less clear. We estimated aldosterone secretion indirectly in 715 children, 249 of whom were black, by measuring their nocturnal rates of urinary excretion of aldosterone. Dietary sodium and potassium intakes were estimated from their excretion rates. The mean (+/- SE) aldosterone-excretion rate was lower in the black children than in the white children (0.045 +/- 0.003 vs. 0.078 +/- 0.004 nmol per micromole of creatinine per kilogram of body weight; P less than 0.001). The potassium-excretion rate was also lower in the black children than in the white children (0.13 +/- 0.01 vs. 0.18 +/- 0.01 mmol per micromole of creatinine per kilogram; P less than 0.001). Aldosterone excretion was highly correlated with potassium excretion (P less than 0.001), but the lower aldosterone-excretion rate in blacks was explained only in part by their lower dietary intake of potassium. Systolic blood pressure was higher in black children (P less than 0.001), as was diastolic pressure (P = 0.037). In a second study of 99 children, the plasma aldosterone level was found to be significantly lower in black children than in white children (230 +/- 30 vs. 400 +/- 30 pmol per liter; P less than 0.001). Plasma renin activity and plasma cortisol levels were the same in both groups. In summary, we found that black children secrete about 40 percent less aldosterone than white children. The role of the lower aldosterone-secretion rate in the genesis of the higher blood pressures observed in black children is not known.