THE 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 the regulation of glomerulosa tissue growth an d function, and in mediating the response of the tissue to stimulation by ACTH and potassium ions. To examine the role of the rat adrenal ti ssue RAS in its response to angiotensin II stimulation, adrenals were incubated either as bisected glands or as separated capsular glands (l argely glomerulosa) under control conditions, or in the presence of th e angiotensin-converting enzyme inhibitor captopril, or of angiotensin II, or both. Captopril inhibited the two different tissue preparation s in different ways. In the capsular gland it inhibited basal aldoster one output, but facilitated its response to angiotensin II. In the bis ected gland, captopril inhibited the response of aldosterone to angiot ensin II. Other data suggest that one way in which captopril functions is by preventing the conversion of fasciculata-generated 18-hydroxyde oxycorticosterone (18-OH-DOC) to aldosterone in the glomerulosa. Immun olocalisation of 18-OH-DOC in perfused rat adrenal confirms that one f unction of angiotensin II is to mobilise tissue-sequestered 18-OH-DOG. The results illustrate the importance of tissue RAS in the synthesis of aldosterone and the response to angiotensin II.