ROLE OF THE TISSUE RENIN-ANGIOTENSIN SYSTEM IN THE RESPONSE OF THE RAT ADRENAL TO EXOGENOUS ANGIOTENSIN-II

The tissue renin angiotensin systems (RAS) may have specific roles tha t complement those of the systemic RAS. In the adrenal, the tissue RAS has been implicated in mediating the response of the tissue to stimul ation by ACTH and potassium ions, but its role in the response to angi otensin II stimulation has not been addressed. To examine this, rat ad renals were incubated either as bisected glands or as separated capsul ar glands (largely glomerulosa) under control conditions, or in the pr esence of the angiotensin converting enzyme inhibitor captopril, or of angiotensin II, or both. Captopril inhibited the two different tissue preparations in different ways. In the capsular gland it inhibited ba sal aldosterone output, but facilitated its response to angiotensin II . In the bisected gland, captopril inhibited the response of aldostero ne to angiotensin II. The results illustrate the importance of the tis sue RAS in the synthesis of aldosterone and the response to angiotensi n II, and the two sets of data suggest that the fasciculata and glomer ulosa zones interact in the formation of aldosterone. One way in which this may occur is by the mobilisation of fasciculata synthesised subs trate, such as 18-hydroxydeoxycorticosterone (18-OH-DOC), for conversi on by the glomerulosa, which is apparently supported by endogenous ang iotensin II.