Corticotropin-like peptides in central nerves and in endocrine cells of gut and pancreas

Abstract

Extrapituitary corticotropin-like peptides have been found in central nerves and in gastrointestinal and pancreatic endocrine cells. Previous biological and immunological data strongly indicate that the immunoreactivity present in the central nerves represents corticotropin (A.C.T.H.) or a closely related peptide. In some areas of the brain, the distribution of A.C.T.H. nerves parallels that of nerves containing the endogenous opioid ligand, enkephalin. Since A.C.T.H. fragments bind to the opioid receptor the two neuronal peptides may interact. The antiserum used demonstrates the COOH-terminus of the A.C.T.H. molecule, which is devoid of adrenocortical stimulatory activity. A COOH-terminal A.C.T.H.-peptide, corticotropin-like intermediate peptide (C.L.I.P.), originally isolated from the pars intermedia, has been shown to stimulate release of pancreatic insulin. The presence of C.L.I.P.-like molecules in gut and pancreatic endocrine cells may indicate that C.L.I.P.'s insulin-releasing activity is physiologically important. Further, the occurrence of A.C.T.H.-related molecules in such cells may account for the ectopic A.C.T.H. syndrome associated with some tumours of gut and pancreas.