Regulation of bioactive beta-endorphin processing in rat pars intermedia.
Acid extracts of rat pituitary neuro-intermediate lobes have been shown by ion-exchange chromatography and radio-immunoassay to contain predominantly the inactive derivatives of beta-endorphin, alpha, N-acetyl beta-endorphin 1-27 and alpha, N-acetyl beta-endorphin 1-26; the biologically active form, beta-endorphin 1-31, is a minor component. In contrast, it was found that beta-endorphin generated in neuro-intermediate lobe cells in monolayer culture was less processed: the principal peptides related to bioactive beta-endorphin 1-31. When the cultured cells were incubated in the presence of 10(-5) M dopamine or 10(-6) M alpha-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 alpha-N-acetyl beta-endorphin 1-26 and alpha, N-acetyl beta-endorphin 1-27 as the prominent peptides. The results demonstrate that dopaminergic agents can influence the processing of beta-endorphin-related peptides in rat pars intermedia, indicating a new level at which the bioactivity may be regulated.
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D002478:Cells, Cultured; D002852:Chromatography, Ion Exchange; D004298:Dopamine / Q000494:pharmacology; D004723:Endorphins / Q000096:biosynthesis* / Q000302:isolation & purification; D007700:Kinetics; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
D004723:Endorphins; D001971:Bromocriptine; D001615:beta-Endorphin; D004298:Dopamine