Effect of food intake on the metabolic clearance rate of aldosterone.

The effect of eating on the metabolic clearance rate (MCR) of aldosterone was investigated in 10 adult individuals. 3H-aldosterone was infused continuously over a period of 5 h while the subjects remained supine. Three h after the start of the infusion, each subject ate a bowl of soup. The MCR of aldosterone, before and after the intake of food, was calculated by dividing the rate of infusion of 3H-aldosterone by the mean concentration of under the same conditions but without eating. The MCR of aldosterone (mean +/- 1 SD) was 1284 +/- 513 L/24 h before food intake and 2182 +/- 180 L/24 h after food intake in the 10 individuals who ate. The MCR in the 11 subjects who did not eat was 1363 +/- 446 and 1357 +/- 434 during the same periods (p greater than 0.05). The 29% increase in the MCR induced by eating was highly significant (p less than 0.001); it was similar in magnitude and duration to a previously reported effect of food intake on the hepatic blood flow (13).

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.