A dynamic study of plasma renin activity and aldosterone concentration in normal and hypertensive subjects

Variations of plasma renin activity (PRA) and plasma aldosterone concentration have been studied after a water load with a 2-hour period of recumbency followed by furosemide infusion in five normal subjects and seven hypertensive patients. It has been found following furosemide infusion that there is a lag of 15 min between the increase in PRA and that of aldosterone. PRA and aldosterone levels are still elevated when diuresis and natriuresis have returned close to normal. Patients with essential hypertension behave like normal subjects during this dynamic test except for one patient with abnormally low PRA and low normal levels of plasma aldosterone. The two patients with primary aldosteronism were able to modify their aldosterone concentration as normal subjects did, but at all times their levels remained higher. Plasma aldosterone concentration as a diagnostic screening test should be performed in the upright position.