Estradiol-17beta triggers luteinizing hormone release in the protandrous black porgy (Acanthopagrus schlegeli Bleeker) through multiple interactions with gonadotropin-releasing hormone control.
We investigated the mechanism of estradiol-17beta (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-17beta 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-17beta 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 E2in the sex change observed in the protandrous black porgy.
Yen
Fan-Pin
FP
Department of Aquaculture, National Taiwan Ocean University, Keelung 202, Taiwan, Republic of China.
Lee
Yan-Horn
YH
He
Chun-Lin
CL
Huang
Jing-Duan
JD
Sun
Lian-Tien
LT
Dufour
Sylvie
S
Chang
Ching-Fong
CF
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D010473:Perciformes / Q000378:metabolism*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone