title: Dopaminergic agents selectively alter the post-translational processing of beta-endorphin in the intermediate pituitary of the rat.
abstract: The present study examines whether sustained changes in the biosynthetic activity of the intermediate pituitary, induced pharmacologically by treating rats with dopamine receptor ligands, alters the post-translational processing of beta-endorphin (beta-END). Separation of the individual molecular forms of beta-END using ion exchange chromatography revealed that beta-END is processed to alpha-N-acetylated and nonacetylated forms of beta-END-(1-31), beta-END-(1-27) and beta-END-(1-26) in the neurointermediate lobe (NIL). Chronic treatment with D-2, but not D-1, dopamine receptor antagonists elevated total beta-END immunoreactivity (i beta-END) in the NIL but this increase was predominantly attributable to elevations in the concentrations of N-acetyl-beta-END-(1-31) and N-acetyl-beta-END-(1-27). In contrast, N-acetyl-beta-END-(1-26) was not significantly affected. The dopaminergic agonist, bromocriptine, had the opposite effect; it lowered total i beta-END levels, depleting N-acetyl-beta-END-(1-31) and N-acetyl-beta-END-(1-27) to a greater extent than N-acetyl-beta-END-(1-26). beta-END peptides were released in vitro in the same relative proportion as they were contained in the NIL suggesting that individual molecular forms of beta-END are not released preferentially. i gamma-END levels also were modulated by dopaminergic agents but the processing of gamma-END and alpha-END was not altered. Acute haloperidol treatment depleted i gamma-END levels but did not affect the pattern of beta-END peptides in the NIL. These results indicate that dopaminergic agents influence not only the secretion but also the post-translational processing of pituitary beta-END.
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D001971:Bromocriptine / Q000494:pharmacology; D004294:Domperidone / Q000494:pharmacology; D018492:Dopamine Antagonists; D004873:Ergolines / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D001615:beta-Endorphin / Q000235:genetics*
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D004873:Ergolines; D011954:Receptors, Dopamine; D019257:Quinpirole; D001971:Bromocriptine; D004294:Domperidone; D001615:beta-Endorphin; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D006220:Haloperidol