Vasoactive intestinal peptide stimulation of aldosterone secretion by the rat adrenal cortex may be mediated by the local release of catecholamines

The effects of vasoactive intestinal peptide (VIP) on adrenocortical function were investigated using several different preparations of adrenocortical tissue. VIP caused a significant increase in perfusion medium flow rate and in aldosterone and corticosterone secretion by the isolated perfused rat adrenal gland, with a threshold of 1 pmol in 200 microliters, but did not affect basal steroid secretion by collagenase-dispersed adrenocortical cells at any concentration used, from 10 pmol/l to 10 mumol/l. The presence of VIP (100 nmol/l) had no significant effect on the response of zona glomerulosa cells to stimulation by ACTH at any concentration. In incubations of intact adrenal capsular tissue, VIP (10 mumol/l) caused a significant stimulation of aldosterone secretion, and also induced a significant release of adrenaline into the incubation medium. Addition of (-)alprenolol (100 nmol/l), a beta-adrenergic antagonist, to the incubation medium significantly attenuated the response of capsular tissue to VIP. It is concluded that the effects of VIP on aldosterone, which are only seen when the architecture of the zona glomerulosa is preserved, may be mediated by the local release of adrenaline.