Corticotrophin-related peptides in the intermediate lobe of the rodent pituitary gland: characterization by high performance liquid chromatography and radioimmunoassay.

High performance liquid chromatography (HPLC) and radioimmunoassay have been used to characterize corticotrophin-related peptides in extracts of the intermediate lobe of the rat and mouse pituitary gland. Multiple peaks have been observed, which resemble corticotrophin-like intermediate lobe peptide (CLIP) in that they cross-react with antisera raised against the COOH-terminal region of corticotrophin (ACTH) but not against NH2-terminal directed antisera. These CLIP-like peptides were released from the incubated neurointermediate lobe and their secretion was inhibited in the presence of dopamine. Heterogeneity of peptide species was also observed with antisera raised against alpha-MSH. Multiple peaks of CLIP and alpha-MSH-like material were identified in pituitary extracts from the mouse and levels were elevated in the genetically obese (ob/ob) animal. The nature and possible functions of multiple forms of intermediate lobe peptides are discussed.