Comparison of the effects of VIP and PACAP on steroid secretion of dispersed rat adrenocortical cells

The effects of vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP)-38 or -27, and their receptor antago nists (VIP-A, P38-A and P27-A) have been investigated on aldosterone and co rticosterone secretion in dispersed rat zona glomerulosa (ZG) and zona fasc iculata-reticularis (ZF/R) cells. VIP and PACAP-38 enhanced both aldosteron e and corticosterone production, VIP being much more effective than PACAP-3 8. PACAP-27 elicited only a moderate increase in corticosterone production. The ACTH receptor antagonist corticotropin-inhibiting peptide and the beta -adrenoceptor antagonist l-alprenolol did not affect hormonal response to t he maximal effective concentration (10(-6) M) of VIP and PACAPs. VIP-A, whi ch is an antagonist of VPAC1 receptor subtype, counteracted only corticoste rone response to PACAP-38. P38-A, which is an antagonist of PAC1 receptor a nd VPAC2 receptor subtypes, hampered aldosterone response to VIP and PACAP- 38, and corticosterone response to VIP and PACAP-27. P27-A, whose receptor selectivity is not known. VIP-A potentiated corticosterone response to VIP, and aldosterone response to PACAP-38. These findings led us to conclude: ( i) VIP and PACAPs stimulate secretion of rat adrenocortical cells, through the activation of specific receptors, being their effectiveness VIP>PACAP-3 8 > >PACAP-27; and (ii) aldosterone response of ZG cells to VIP and PACAPs is probably mediated by PAC(1) and VPAC(2) receptors, while corticosterone response of ZF/R cells involves also the VPAC(1) receptor subtype.