title: Regulation of the type-II gonadotrophin alpha and beta subunit mRNAs by oestradiol and testosterone in the European eel.
abstract: The gonadotrophic function of the European eel (Anguilla anguilla L.) at the silver stage is very weak: gonadotrophin-releasing hormone (GnRH) secretion is deficient and, moreover, dopamine inhibition overrides GnRH action. At the silver stage, oestradiol stimulates the biosynthesis of the type-II gonadotrophin (GTH-II). To study the molecular mechanism of this activation further, we examined the effect of testosterone and oestradiol administration on pituitary levels of mRNA encoding GTH-II alpha and beta subunits. Corresponding eel cDNA probes and Northern blot analysis were used. After 2 weeks, testosterone and oestradiol implantation resulted in a strong increase in mRNA encoding the GTH-II beta subunit (7-fold and 25-fold, respectively) and in a slight, but non-significant, rise in the a subunit mRNA level (1.8-fold and 1.5-fold, respectively). Co-implantation of these two steroids suggested a potentiation of their effects on the beta subunit (104-fold) while an additive effect was indicated on the alpha mRNA level (2.9-fold). Effects were detectable within 4 days and were maximal 4 weeks after implantation. These results indicate that in the European eel at the silver stage, gonadal steroids stimulate differentially the expression of GTH-II subunit genes at a pretranslational level.
authors.affiliation: Laboratoire de Physiologie Générale et Comparée du MNHN, Unité d'Endocrinologie Comparée du CNRS, URA 90, Paris, France.
authors.forename: B
authors.initials: B
authors.lastname: Quérat
authors.forename: A
authors.initials: A
authors.lastname: Hardy
authors.forename: Y A
authors.initials: YA
authors.lastname: Fontaine
mesh_terms: D000811:Anguilla / Q000235:genetics*; D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D006065:Gonadotropins, Pituitary / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology*
chemical_list: D006065:Gonadotropins, Pituitary; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D004958:Estradiol