Plasma renin activity in hypertensive diseases.

Plasma renin activity was determined in normotensive and hypertensive human subjects by a modification of the method of Boucher and co-workers. Simultaneous determination of plasma volume, serum electrolyte concentration and plasma renin activity was performed. The plasma renin activity was normal in essential hypertension and in pheochromocytoma, normal or subnormal in Cushing's syndrome with adrenal hyperplasia, increased in Cushing's syndrome with adrenal carcinoma and in renal or renovascular hypertension and decreased in primary aldosteronism. Three hours after taking upright posture, patients with essential hypertension showed two to fivefold increase of plasma renin activity, while those with primary aldosteronism did not. In renovascular hypertension and primary aldosteronism, plasma renin activity returned to normal range after operation. Diurnal variation of plasma renin activity was investigated under a standard condition. In normotensive subjects, highest value was observed in the forenoon and lowest value in the afternoon. As respects the diurnal variation of plasma renin activity, an inverse relationship between plasma renin activity and plasma volume was exhibited.