THE ROLE OF BOMBESIN IN REGULATING RAT PITUITARY-ADRENOCORTICAL FUNCTION

The effects of a 7-day administration of bombesin (BM) and/or [Tyr(4), D-Phe(12)]- BM, a BM-receptor antagonist (BM-A), on the function of p ituitary-adrenocortical axis were investigated in the rat. BM raised t he plasma concentration of aldosterone, without affecting that of ACTH or corticosterone, the simultaneous administration of BM-A prevented the effect of BM. Neither BM nor EM-A treatments induced significant c hanges in adenohypophysis and adrenal weights, as well as in the avera ge volume of zona glomerulosa and zona reticularis cells. BM-A adminis tration lowered the volume of zona fasciculata cells, an effect annull ed by the concomitant BM administration. Our results suggest that BM s pecifically stimulates aldosterone secretion, and that endogenous BM o r BM-like peptides exert a tonic stimulating action on the growth of z ona fasciculata cells.