title: Inhibitory effect of beta-endorphin on gonadotropin-releasing hormone and thyrotropin-releasing hormone releasing activity in cultured rat anterior pituitary cells.
abstract: To study the effect of human beta-endorphin (beta h-End) on pituitary response to gonadotropin-releasing hormone (LH-RH) and thyrotropin-releasing hormone (TRH) in vitro, we used dispersed rat pituitary cells. When beta h-End (10(-7) M) was simultaneously added along with LH-RH, its stimulatory effect was blocked and naloxone (NAL, 10(-5) M) did not reverse the beta h-End inhibitory effect. NAL alone elicited an increase in LH release, but in the presence of both stimulants (LH-RH and NAL), LH secretion was lower than that observed with LH-RH alone. TRH stimulatory activity of TSH and PRL secretion was blunted by the presence of beta h-End (10(-7) M) and was not reversed by NAL (10(-5) and 10(-3) M). These data suggest that beta h-End directly blocks the LH, TSH- and PRL-secreting activity of both LH-RH and TRH at the pituitary level. This beta h-End effect is not reversed by the specific opiate receptor blocker NAL.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004723:Endorphins / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D007987:Gonadotropin-Releasing Hormone; D009270:Naloxone; D013973:Thyrotropin-Releasing Hormone; D001615:beta-Endorphin; D011388:Prolactin; D007986:Luteinizing Hormone