Luteinizing hormone-β mRNA levels are regulated primarily by gonadotropin-releasing hormone and not by negative estrogen feedback on the pituitary

Abstract

Long-term effects of gonadotropin-releasing hormone (GnRH) and/or estrogen on pituitary mRNA levels for the β-subunit of luteinizing hormone (LH-β) were determined in anterior pituitary glands from ovariectomized (OVX) ewes. The relative roles of these two factors were assessed by studying hypothalamopituitary disconnected (HPD) ewes with appropriate hormonal treatments. Levels of LH-β mRNA were increased by ovariectomy and substantially reduced by HPD. Treatment of OVX-HPD ewes with pulses of GnRH (250 ng each 2 h) for 1 week restored LH-β mRNA levels to OVX levels, whereas treatment with estrogen alone did not alter the low levels found in OVX-HPD ewes. Combined GnRH and estrogen treatment..