Pro-opiocortin fragments in human and rat brain: beta-endorphin and alpha-MSH are the predominant peptides.

The 'pro-opiocortin' fragments, beta-lipotropin, beta-endorphin, ACTH and alpha-MSH, were estimated in discrete areas of rat and human brain and pituitaries by means of radioimmunoassay in combination with gelfiltration. These peptides exhibited parallel patterns of distribution, but with beta-endorphin and alpha-MSH predominant in the brain of rat and man, and, in contrast, their respective precursors. beta-LPH and ACTH predominant in the adenohypophysis of rat and man. These data may be indicative of important differences in post-translational processing of 'pro-opiocortin' between these contrasting tissues.