Role of adrenal renin-angiotensin system in the control of aldosterone secretion in sodium-restricted rats

This study examined the effect of the pharmacological manipulation of adren al renin-angiotensin system (RAS) on aldosterone secretion from in situ per fused adrenals of rats kept on a normal diet and sodium restricted for 14 d ays. Neither the angiotensin-converting enzyme inhibitor captopril nor the nonselective angiotensin II receptor antagonist saralasin and the AT(1) rec eptor-selective antagonist losartan affected basal aldosterone output in no rmally fed rats. In contrast, they concentration dependently decreased aldo sterone secretion in sodium-restricted animals, with maximal effective conc entration ranging from 10(-7) to 10(-6) M. Captopril (10(-6) M), saralasin (10(-6) M), and losartan (10(-7) M) counteracted aldosterone response to 10 mM K+ in sodium-restricted rats but not in normally fed animals. Collectiv ely, these findings provide evidence that adrenal RAS plays a role in the r egulation of aldosterone secretion, but only under conditions of prolonged stimulation of zona glomerulosa probably leading to overexpression of adren al RAS.