[Renin-angiotensin-aldosterone system with regard to age]

Ninety seven practically healthy subjects were examined, grouped into three age groups. The functional state of renin-angiotensin-aldosterone system (RAAS) was assessed by the determination of plasma renin activity (PRA), plasma aldosterone (PA) and aldosterone urine excretion. Two dynamic tests were used--orthostatic test and a diet with restricted sodium content (hypo-natritm diet). The results obtained reveal that RAAS activity is reduced with age advancing, manifestations of which are the reduced mean values of PRA, PA and aldosterone urine excretion. The response of renin-angiotensin system to volume stimuli in elderly and aged people, is reduced (orthostatism) whereas the reactivity of sodium elimination is preserved. The role of sympathetic nervous system as a cause of age changes of PRA is discussed.