Inhibitory and Facilitatory Effects of Estradiol 17β on Pituitary Responsiveness to a Luteinizing Hormone-Follicle Stimulating Hormone Releasing Factor (LH-RF/FSH-RF) Preparation in the Ovariectomized Rat

Abstract

Summary

A single intravenous injection of 200 ng of estradiol significantly depressed both LH release in vivo for up to 9 hr and unstimulated LH and FSH release in vitro at 3 hr. The releasing factor preparation evoked significantly less LH release in vivo at 3 hr after estradiol than in saline-injected controls; however, by 6–9 hr after estradiol, the response to LH-RF/FSH-RF stimulation was noticeably enhanced for both LH and FSH release in vitro and in vivo when compared to the response in the ovariectomized controls, even though plasma LH was still suppressed.

It is concluded that subsequent to an initial suppression of gonadotroph sensitivity to LH-RF/FSH-RF stimulation, there is an augmented hypophyseal responsiveness to the releasing factor following estrogen treatment.