Comparative effects of ACTH, PACAP, and VIP on fetal human adrenal cells

ACTH is a well-known stimulus of human adrenal cells, both in the adult and in the fetus. Two other stimuli, acting via the cAMP pathway, are also involved in the regulation of steroidogenesis and growth of the adult gland, the Pituitary Adenylate Cyclase Activating Peptide (PACAP) and the Vasoactive Intestinal Polypeptide (VIP). The aim of this study was to compare the effects of the three peptides on cAMP production and to investigate their possible effect on cytoskeletal organization in the different cell types present in the human fetal adrenal gland, i.e steroidogenic cells and chromaffin cells. Using phalloidin-rhodamine labeling of actin microfilaments, we observed that VIP and ACTH strongly affect cytoskeletal organization. Application of ACTH rapidly induces steroidogenic cells to elaborate fillopodia and junctions with neighboring cells. Application of VIP strongly stimulates the chromaffin cells to elaborate neurite-like extensions, suggesting that the effects of VIP could be, as in adult glands, mediated by the adrenal medulla.