The integrated concentration of plasma renin activity and aldosterone in essential hypertension.

Measurement of the integrated concentration is most suited for the study of blood components that fluctuate rapidly. The integrated concentration of plasma aldosterone (IC-ALDO) and plasma renin activity (IC-PRA) were measured in 24 patients with essential hypertension and in 10 normal adult subjects, using a non-thrombogenic 24-hour constant blood withdrawal system. The integrated concentration of plasma aldosterone in the control subjects was 7.7 +/- 1.8 ng/100 ml (mean +/- 1 SD). Eight hypertensive patients had IC-ALDOs that were more than 3 standard deviations above the mean. Although the mean IC-PRA of the hypertensive patients was lower than the mean of controls (0.6 +/- 0.6 and 0.9 +/- 0.6, respectively), the difference was not significant. However, high integrated concentration of plasma aldosterone was mostly associated with low integrated concentration of plasma renin activity. Consequently, the ratio of IC-ALDO to IC-PRA in the hypertensive patients was significantly higher (p less than 0.001). In six hypertensive patients the ratio was more than 4 standard deviations above the mean for the normal control subjects (12.2 +/- 7.6). Individuals with inappropriately high integrated concentrations of plasma aldosterone can therefore be identified by the simultaneous determination of IC-ALDO and IC-PRA.