Biosynthesis of pro-opiomelanocortin-related peptides in the neurointermediate lobe of the pituitary gland of the rainbow trout (Salmo gairdneri).

This study concerns the biosynthesis of a number of peptides in the neurointermediate lobe of the rainbow trout, Salmo gairdneri. Among the newly synthesized peptides positively identified were four forms of alpha-MSH, a beta-MSH and two forms of endorphin. The identification of two of the products as sequentially distinct endorphins suggests that the trout neurointermediate lobe synthesizes two pro-opiomelanocortin (POMC) molecules. This may account for the large number of peptides synthesized and secreted by the trout neurointermediate lobe. The identification of some of the products is discussed. Pulse-chase analysis revealed no positive identification of a precursor molecule, which may indicate that trout POMC is very rapidly processed into smaller products. All of the newly synthesized peptides were secreted concomitantly. There was little if any evidence of post-translational modification of any of the peptides during their secretion.