Mechanism of Age‐Related Changes in Renin and Adrenocortical Steroids

Age‐related changes in plasma renin activity (PRA) and in plasma levels of adrenocortical steroids were studied in 140 normotensive men and 128 normotensive women. All were free of disease, and their ages ranged from 20 to 86 years. PRA decreased gradually with age in both men and women, and was slightly lower in women than in men. In the older subjects, the responses of PRA to the administration of furosemide or to dietary sodium restriction plus the upright position for blood sampling were significantly less than in the younger subjects. Apparently the suppression of PRA with age is due either to dysfunction of the juxtaglomerular cells induced by aging, or to reduction in the number of functioning nephrons. The plasma level of aldosterone was also reduced with age, but the levels of desoxycorticosterone, corticosterone, and cortisol were not significantly affected. The suppression of aldosterone seemed to be chiefly dependent upon the suppression of renin activity. However, the possibility remains that disturbed function of the glomerular cells with aging also is related to the suppression of aldosterone, since the response of aldosterone to dietary sodium restriction (upright position for blood sampling), to angiotensin II, and to potassium were greatly reduced.