Dopamine-inhibited release of prolactin and intermediate lobe-POMC-peptides: different modulation by opioids.
Primary monolayer cultures of anterior or intermediate lobe (IL) cells from rat pituitaries were grown in microtiter plates, and the test substances were added after 5 days. The hormones were measured by RIAs for rat prolactin,  -MSH, ACTH and beta-endorphin/beta-LPH. The dopamine (DA) inhibition of prolactin secretion was attenuated by addition of equimolar (10(-7), 10(-6)M) concentration of beta-endorphin. Furthermore, the DA effect was blocked, when the beta-endorphin-release of anterior pituitary cells was stimulated by vasopressin. In contrast, the DA induced inhibition of hormone-release of IL-cells (e.g.  -MSH, ACTH and beta-endorphin) was not influenced by addition of opioids. Our results indicate, that under certain conditions (e.g. stress) the stimulated secretion of prolactin could be mediated partially by a direct action of pituitary beta-endorphin at the lactotroph. On the other hand, we found no indication for a modulation of the dopamine-induced inhibition of IL-peptides by opioids.
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology*; D004723:Endorphins / Q000378:metabolism*; D005260:Female; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D010908:Pituitary Hormones, Anterior / Q000378:metabolism*; D011333:Pro-Opiomelanocortin; D011388:Prolactin / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin; D008083:beta-Lipotropin / Q000378:metabolism*
D004723:Endorphins; D010908:Pituitary Hormones, Anterior; D011498:Protein Precursors; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D009074:Melanocyte-Stimulating Hormones; D008083:beta-Lipotropin; D004298:Dopamine