Levels of mineralocorticoids in whites and blacks

Blacks appear, on average, to retain more Na than whites. A higher producti on rate of mineralocorticoids could explain the greater Na retention in bla cks. Although production of aldosterone has been shown to be lower in black s, the level of another mineralocorticoid may be increased. Plasma levels o f deoxycorticosterone and cortisol were measured in young whites (n=23; age =16.4+/-3.1[SD] years) and young blacks (n=25; age=13.8+/-1.3 years). Black s had lower plasma levels of renin activity and aldosterone and lower urina ry aldosterone excretion rates; thus, they appeared to be representative of blacks that retain additional Na. Plasma deoxycorticosterone levels were l ower in blacks than in whites both at baseline (247+/-161 versus 381+/-270 pmol/L, P=0.048) and after stimulation with adrenocorticotropic hormone (82 2+/-294 versus 1127+/-628 pmol/L at 30 minutes, P=0.047; 925+/-366 versus 1 440+/-834 pmol/L at 60 minutes, P=0.013). Cortisol levels were also lower i n blacks at baseline (P=0.014) but were not significantly different from le vels in whites after stimulation with adrenocorticotropic hormone. In a lar ger cohort of 407 whites (age=12.0+/-2.9 years) and 247 blacks (age=12.9+/- 3.1 years), 18-hydroxycortisol excretion rates were also lower in blacks (P =0.021). In conclusion, increased Na retention in blacks does not appear to be secondary to increased production of either aldosterone, deoxycorticost erone, cortisol, or 18-hydroxycortisol, A primary renal mechanism may media te the increase in Na reabsorption in blacks.