Secretion of pro-opiocortin peptides from isolated perfused rat pars intermedia cells.
The perfused, isolated, pituitary cell column was used to measure the release of alpha-melanotropin (alpha-MSH)-like immunoreactivity (LI), carboxyl terminal corticotropin (C-ACTH)-LI, gamma-lipotropin (gamma-LPH)-LI, alpha-endorphin-LI, beta-endorphin-LI and amino-terminal pro-opiocortin (N-POC)-LI from rat pars intermedia (PI) cells. Concomitant secretion of all PI peptides was observed during basal release and in response to all applied stimuli. Dopamine (DA) caused a dose-dependent (10(-9)-10(-5) M) simultaneous inhibition of peptide release which was antagonised by haloperidol. Isoprenaline stimulated the release of PI peptides in a parallel, dose-related (10(-10)-10(-6) M) manner and was blocked by propranolol. Stimulation of peptide secretion caused by low concentrations (10(-8) M), of adrenaline (AD) and noradrenaline (NA) changed to inhibition at high concentrations (10(-5) M) whereas intermediate concentrations (10(-6), 10(-7) M) possessed both inhibitory and excitatory effects. A 45 mM solution of K+ ions stimulated the release of PI peptides and both the K+-stimulated secretion and basal secretion were Ca++-dependent. MSH-release-inhibiting factor (MIF) and 5-hydroxytryptamine (5-HT) failed to alter peptide secretion from the perfused PI cells. We conclude that pro-opiocortin (POC) peptides are released concomitantly from rat PI cells and that biogenic amines are involved in their release.
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D003470:Culture Media; D004298:Dopamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004723:Endorphins / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D010908:Pituitary Hormones, Anterior / Q000378:metabolism*; D011333:Pro-Opiomelanocortin; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D018822:alpha-Endorphin; D001615:beta-Endorphin; D008083:beta-Lipotropin / Q000378:metabolism
D003470:Culture Media; D004723:Endorphins; D010908:Pituitary Hormones, Anterior; D011498:Protein Precursors; D001615:beta-Endorphin; D018822:alpha-Endorphin; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D008083:beta-Lipotropin; D007545:Isoproterenol; D004298:Dopamine; D004837:Epinephrine