EFFECTS OF BRADYKININ ON THE SECRETORY ACTIVITY OF DISPERSED ZONA-FASCICULATA RETICULARIS CELLS OF THE RAT ADRENAL-CORTEX

The presence of an intra-adrenal kallikrein-kinin system suggests the possible involvemen of bradykinin (BK) in the regulation of adrenal fu nctions. The present investigation aimed to study whether BK exerts a direct effect on glucocorticoid secretion of rat adrenals. BK concentr ation-dependently raised basal corticosterone (B) secretion of dispers ed zona fasciculata/reticularis (ZF/R) cells, and this effect was conn ected with a clear-cut intracellular Ca2+ mobilization. The secretagog ue action of BK was completely blocked by D-Arg,[Hyp(3),DPhe(7)]-BK, a specific BK-receptor antagonist (BK-A), that per se did not change ba sal B secretion. Conversely, both BK and BK-A concentration-dependentl y inhibited maximally ACTH-stimulated B production by dispersed ZF-R c ells. In light of these findings it may be hypothesized that BK exerts a two-fold direct effect on the function of adrenal ZF/R in rats: (i) stimulation of basal glucocorticoid secretion via a receptor-mediated mechanism, and (ii) inhibition of ACTH-stimulated one by a receptor-i ndependent mechanism probably involving the interference with the intr acellular mechanism(s) transducing the ACTH secretagogue signal.