We investigated the mechanism of estradiol-17β (E2) action on stimulation of LH (=gonadotropin II) release in the black porgy fish (Acanthopagrus schlegeli Bleeker) using an in vivo approach and primary cultures of dispersed pituitary cells in vitro. In vivo, E2 but not androgens (testosterone [T] and 11-ketotestosterone [11-KT]) significantly stimulated plasma LH in a dose-dependent manner. Estradiol-17β also increased brain content of seabream GnRH. GnRH antagonist prevented E2 stimulation of LH release in vivo, indicating that the effect of E2 on LH was mediated by GnRH. In vitro, sex steroids (E2, T, 11-KT) alone had no effect on basal LH release in the cultured pituitary cells, but GnRH significantly stimulated LH release. Estradiol-17β potentiated GnRH stimulation of LH release, an effect that was inhibited by GnRH antagonist, and 11-KT, but not T, also potentiated GnRH stimulation of LH release. The potentiating effect of 11-KT on GnRH-induced LH release in vitro was stronger than that of E2. These data suggest that E2 triggers LH release in vivo by acting both on GnRH production at the hypothalamus and on GnRH action at the pituitary. In contrast, 11-KT may only stimulate GnRH action at the pituitary. The E2 induction of LH release, through multiple interactions with GnRH control, supports a possible central role of E2 in the sex change observed in the protandrous black porgy.
How to translate text using browser tools
1 January 2002
Estradiol-17β Triggers Luteinizing Hormone Release in the Protandrous Black Porgy (Acanthopagrus schlegeli Bleeker) Through Multiple Interactions with Gonadotropin-Releasing Hormone Control
Fan-Pin Yen,
Yan-Horn Lee,
Chun-Lin He,
Jing-Duan Huang,
Lian-Tien Sun,
Sylvie Dufour,
Ching-Fong Chang
ACCESS THE FULL ARTICLE
<
Previous Article
|
estradiol
gonadotropin-releasing hormone
luteinizing hormone
testosterone