Circadian Rhythm of Renin and Aldosterone in Unilateral Renovascular Hypertension

The circadian rhythm of plasma renin activity and plasma aldosterone levels was determined in 11 normal subjects and 7 patients with unilateral renovascular hypertension, while upright and while recumbent. Plasma renin activity tended to be higher in patients with unilateral renovascular hypertension than in the normal subjects. Every patient with unilateral renovascular hypertension had an elevated plasma renin activity with 12 hours of upright posture. Changes in plasma aldosterone levels were not as striking. Three patients were restudied after surgical correction of their unilateral renovascular hypertension: the circadian rhythm had returned to normal, and the plasma renin activity and plasma aldosterone levels had decreased from preoperative values. These results suggest that chronic unilateral renovascular hypertension is associated with activation of the renin-angiotensin-aldosterone system, which results in increased circulating levels of plasma renin activity (at least during certain times of the day), when carefully tested.