title: An in vitro bioassay for testing the direct effect of luteinizing hormone-releasing hormone agonists on progesterone secretion by rat ovarian cells.
abstract: It is known that luteinizing hormone-releasing hormone (LHRH) and its agonistic analogs could act directly on various extrapituitary target tissues by activating their specific receptors present in these tissues. In this report, we proposed an in vitro assay method for testing the bioactivities of LHRH agonists based on their inhibitory effect on human chorionic gonadotropin (HCG)-induced progesterone secretion by rat ovarian cells. Ovaries from five to ten pseudopregnant rats (prepared by sequential hormone treatment) were mechanically and enzymatically dispersed to prepare luteal cell-rich suspensions. Addition of [D-Ala6, Pro9-Ethylamide]LHRH to ovarian cell suspensions inhibited different concentrations (1, 10 or 100 mIU/ml) of HCG-induced progesterone secretion in concentration-dependent manners. In the presence of 1 mIU/ml HCG as a stimulant, the percent inhibition of progesterone secretion by the same concentrations of [D-Ala6, Pro9-Ethylamide]LHRH was most pronounced and the results were usually more readily reproducible and with less experimental variations. In this study, LHRH and twelve agonistic analogs (at 10(-9) and 10(-7) M concentrations) were compared for their inhibitory effect on 1 mIU/ml HCG-induced progesterone secretion, and their relative agonistic activities were evaluated based on their inhibition potencies. This in vitro bioassay is simple and time- and cost-efficient, and can be employed as a supplementary method to the commonly utilized bioassays for LHRH agonists. This method may also be useful in screening for LHRH agonists with potent extrapituitary effects.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001681:Biological Assay; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000819:agonists* / Q000494:pharmacology; D006801:Humans; D008969:Molecular Sequence Data; D010053:Ovary / Q000187:drug effects* / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D006063:Chorionic Gonadotropin; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone