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Release of pituitary gonadotrophins GtH I and GtH II in the rainbow trout (Oncorhynchus mykiss): modulation by estradiol and catecholamines

AuthorsSaligaut, Christian; Linard, Boris; Mañanós, Evaristo L. ; Kah, Olivier; Breton, Bernard; Govoroun, Marina
Issue Date1998
PublisherAcademic Press
CitationGeneral and Comparative Endocrinology 109(3): 302-309 (1998)
AbstractThe present study focused on the role of catecholaminergic neurons and estrogens on the release of gonadotrophins I and II in immature and early vitellogenic female rainbow trout. The ovariectomy-induced increase of GtH I blood levels (from about 10 to 15 ng/ml) was prevented in vitellogenic fish by E2 supplementation. E2 implantation of immature fish decreased blood GtH I levels (from about 6 to 1 ng/ml). Blood levels of GtH II were low (about 0.5 ng/ml) and not altered by ovariectomy and E2 treatment. These data demonstrate that estrogens exert a negative feedback on the release of GtH I in trout. A treatment with α-methyl-p-tyrosine (MPT), an inhibitor of catecholamine synthesis, increased blood GtH II levels of sham-operated vitellogenic fish and ovariectomized fish implanted with E2, but had no effects in ovariectomized fish. MPT did not modify blood GtH I levels in any experimental group. A treatment of E2-implanted immature or vitellogenic fish with the dopamine antagonist pimozide also increased blood GtH II levels, but did not significantly change blood GtH I levels. These data demonstrate that release of GtH II, but not of GtH I, depends on an E2-activated DA inhibitory tone.
Identifiersdoi: 10.1006/gcen.1997.7033
issn: 0016-6480
e-issn: 1095-6840
Appears in Collections:(IATS) Artículos
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