EFFECTS OF SECRETIN ON THE FUNCTION OF THE RAT ADRENAL-CORTEX

The effects of secretin administration on the rat adrenal cortex have been investigated both in vitro and in vivo. Secretin significantly ra ised basal aldosterone production by dispersed zona glomerulosa (ZG) c ells, without affecting corticosterone secretion of zona fasciculata ( ZF) and reticularis (ZR) cells. Both the acute and chronic administrat ion of secretin increased the plasma concentrations of ACTH, aldostero ne and corticosterone. The prolonged secretin treatment raised adrenal weight, as well as the volume of ZG and the number of its cells; the average volume of ZF cells was increased, while ZR displayed a marked hyperplasia coupled with a sizable lowering in the volume of its cells . In light of these findings it is concluded that secretin stimulates rat hypothalamo-pituitary-adrenal axis. The secretin-induced rise in c orticosterone secretion and adrenal hypertrophy seems to be exclusivel y due to the stimulation of pituitary ACTH release. In contrast, the i ncrease in aldosterone secretion appears also to involve a direct stim ulatory action of secretin on the ZG.