Short‐Term Regulation of Gonadotropin Subunit mRNA Levels by Estrogen: Studies in the Hypothalamo‐Pituitary Intact and Hypothalamo‐Pituitary Disconnected Ewe

Abstract

In this study the levels of mRNA for the pituitary gonadotropin hormone subunits luteinizing hormone β (LHβ), follicle stimulating hormone β (FSHβ) and the common α‐subunit were assessed during the acute feedback stages of estradiol benzoate (EB) action in ovariectomized (OVX) ewes with and without hypothalamo‐pituitary disconnection (HPD). In OVX/HPD ewes maintained on hourly pulses of 250 μg of gonadotropin‐releasing hormone (GnRH) a single i.m. injection of EB in oil caused a biphasic (decrease and then increase) change in plasma LH levels and a monophasic decrease in FSH levels. There was a decrease in pituitary α‐subunit and FSHβ mRNA levels during the acute negative (8 h post EB) and t..