Estradiol is a major regulator of the reproductive system in females. During periods of greater sensitivity, estradiol prevents normal estrous cycles from occurring. Increased sensitivity to estradiol occurs prior to puberty, postpartum, and in some species, during certain seasons of the year. These periods during which females cannot become pregnant can result in great economic losses to the livestock industry. This project is designed to test how estradiol inhibits the ability of the reproductive hormone, gonadotropin-releasing hormone (GnRH) to induce secretion of luteinizing hormone (LH). Luteinizing hormone is required for normal ovarian function, specifically ovulation. Our hypothesis is estradiol signaling via cell membrane receptors inhibits the ability of GnRH to stimulate secretion of LH. In our first aim we propose to identify
estrogen receptors at the plasma membrane of gonadotropes, cells which secrete LH. In our second aim we propose to determine which component of the GnRH cell signaling pathway is inhibited by estradiol, to disrupt secretion of LH. Currently, no data are available pertaining to membrane estrogen receptors in domestic livestock. It is anticipated that this research can be used to develop analogs of estradiol that could be used in management of domestic livestock to both shorten the periods of greater sensitivity to estradiol and hasten the onset of reproductive cycles.