The influence of aging on the renin-angiotensin-aldosterone system was evaluated by comparing young (20 to 30 yr) with elderly (62 to 70 yr) healthy subjects. Despite comparable body sodium-fluid balance in the two age groups, serum renin concentration, plasma renin activity and aldosterone concentrations were lower in the elderly. The age-related decreases in circulating renin and aldosterone concentrations were slight while subjects were supine and receiving normal sodium intake; when upright and during sodium depletion, they were more pronounced. Inverse renin-blood pressure interrelations were noted during two of four study conditions involving normal sodium intake or mild sodium depletion (r = --0.44 and --0.47, respectively), but not during progressive sodium depletion. Plasma renin levels were decreased in the elderly regardless of the presence or absence of an inverse relationship with blood pressure. Aldosterone and cortisol responses to corticotropin infusion were unaltered in the elderly. It is concluded that aging may cause a decrease in circulating renin, with parallel lowering of plasma aldosterone concentrations.

The activity of the sympathetic nervous system and plasma norepinephrine and endothelin levels are increased during mental stress only in offspring of hypertensive parents, whereas the response to hypoxia was similar in offspring of hypertensive and normotensive parents, suggesting a genetically determined abnormal regulation of the sympathetic nervous system to certain stressful stimuli in offspring of hypertensive parents. This may play a role in the pathogenesis of essential hypertension.

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