In vitro mitogenic and steroidogenic effects of ACTH analogues on an adrenal tumor cell line (Y-1)

Native porcine adrenocorticotropin (ACTH_1–39) as well as synthetic adrenocorticotropin (ACTH_1–24) increase cAMP and steroid production and inhibit DNA synthesis in an adrenal cell line. The COOH terminal sequence of both peptides as well as β-endorphin have no effects, while the NH₂ terminal sequence of ACTH as well as α-MSH which have very low stimulatory effect on cAMP production, have a mitogenic effect. These results suggest that ACTH might have in vitro some mitogenic action on adrenal cell, but this effect is blunted by cAMP accumulation during hormonal stimulation. The results can also explain the in vivo and in vitro contradictory effects of the hormone on adrenal cell replication.