Abstract:The steroidogenic action of ACTH/α-MSH fragments was studied on isolated zona glomerulosa and zona fasciculata cells dispersed by collagenase. ACTH-(4–7), ACTH-(6–10), ACTH-(4–10) and ACTH-(11–13) stimulated corticosterone production of the zona fasciculata and aldosterone production of the zona glomerulosa cells. ACTH-(7–10) was ineffective. ACTH-(4–7) appeared to be the most potent peptide of the tested fragments. None of the fragments affected the steroidogenic action of ACTH-(1–39).