Isolation, characterization, and synthesis of a corticotropin-inhibiting peptide from human pituitary glands.

A corticotropin-inhibiting peptide (CIP) has been isolated from human pituitary extracts. It consists of 32 amino acids with a proposed sequence identical to residues 7--38 of corticotropin (ACTH). The peptide has been synthesized by the solid-phase method. The melanotropic activity of the peptide is estimated to be 30% of the potency of ACTH. It is devoid of corticosteroidogenic activity but is able to inhibit ACTH-stimulated corticosterone production in isolated rat adrenal cells.