Hyperaldosteronism and hypertension - Ethnic differences

The purpose of this study is to evaluate the relationship between aldosterone and blood pressure in a total of 220 normotensive and 293 essential hypertensive subjects in 2 genetically distinct populations - blacks and white French Canadians. The 24-hour blood pressure monitoring was performed under standardized conditions after discontinuing antihypertensive medications. Plasma renin activity and plasma aldosterone were measured in the supine position and after standing for 10 minutes. Plasma atrial natriuretic factor was also measured. Supine and standing plasma renin activities were lower (P <= 0.01), plasma aldosterone was higher (P < 0.0001), and the aldosterone/renin ratios were higher (P < 0.0001) in the hypertensive subjects. Atrial natriuretic factor was also higher in the hypertensive subjects (P < 0.0001). Among blacks, blood pressures did not correlate with plasma renin activity. However, both average daytime and nighttime systolic and diastolic blood pressures were correlated with supine and standing plasma aldosterone and with the aldosterone/renin ratio (P < 0.005 or less). In French Canadians, blood pressures tended to be positively correlated with standing plasma renin activity and aldosterone, but not with the aldosterone/ renin ratio. Correlations of blood pressure with aldosterone were more consistent and more striking in blacks than in French Canadians. In both ethnic groups, there were inconsistent correlations of blood pressure with atrial natriuretic factor. These observations are consistent with the hypothesis that aldosterone-induced volume expansion is an important contributor to hypertension, especially in blacks.