Regulation of bioactive β-endorphin processing in rat pars intermedia

AbstractAcid extracts of rat pituitary neuro-intermediate lobes have been shown by ion-exchange chromatography and radio-immunoassay to contain predominantly the inactive derivatives of β-endorphin, αN-acetyl β-eadorphin 1–27 and α,N-acetyl β-endorphin 1–26; the biologically active form, β-endorphin 1–31, is a minor component. In contrast, it was found that β-endorphin generated in neuro-intermediate lobe cells in monolayer culture was less processed: the principal peptides related to bioactive β-endorphin 1–31. When the cultured cells were incubated in the presence of 10−5 M dopamine or 10−6 M α-ergocryptine there was a marked increase in the degree of proteolysis and acetylation: the processing pattern reverted to that characteristic of the neuro-intermediate lobe in situ, with α-N-acetyl β-endorphin 1–26 and α,N-acetyl β-endorphin 1–27 as the prominent peptides. The results demonstrate that dopaminergic agents can influence the processing of β-endorphin-related peptides in rat pars intermedia, indicating a new level at which the bioactivity may be regulated