The renin-angiotensin-aldosterone system in normal elderly subjects.

In order to observe alterations of the Renin-Angiotensin-Aldosterone (RAA) system in elderly individuals, 40 healthy Venezuelan mestizos (8 men, 32 women) over 60 years of age were examined. These subjects had a normal sodium and potassium diet and were living under normal conditions. Plasma Renin Activity (PRA), urinary and serum aldosterone levels were determined by radioimmunoassay after two hours of ambulation. Values obtained were compared to those of a similar control group under age 60. The study of the RAA system demonstrated a correlation between PRA, serum and urinary aldosterone, and the daily excretion of sodium, even though less significant than in younger subjects. A continuous, gradual descent in these parameters was observed to be related to the advancement of age until approximately age 60, at which time the PRA demonstrated a sudden drop which was not accompanied by a decrease in the level of aldosterone. The most significant changes occur around the sixth decade of life when these hormone levels drop suddenly and the relationship between PRA, urinary and serum aldosterone changes.