title: Intersex occurrence in rainbow trout (Oncorhynchus mykiss) male fry chronically exposed to ethynylestradiol.
abstract: This study aimed to investigate the male-to-female morphological and physiological transdifferentiation process in rainbow trout (Oncorhynchus mykiss) exposed to exogenous estrogens. The first objective was to elucidate whether trout develop intersex gonads under exposure to low levels of estrogen. To this end, the gonads of an all-male population of fry exposed chronically (from 60 to 136 days post fertilization--dpf) to several doses (from environmentally relevant 0.01 µg/L to supra-environmental levels: 0.1, 1 and 10 µg/L) of the potent synthetic estrogen ethynylestradiol (EE2) were examined histologically. The morphological evaluations were underpinned by the analysis of gonad steroid (testosterone, estradiol and 11-ketotestosterone) levels and of brain and gonad gene expression, including estrogen-responsive genes and genes involved in sex differentiation in (gonads: cyp19a1a, ER isoforms, vtg, dmrt1, sox9a2; sdY; cyp11b; brain: cyp19a1b, ER isoforms). Intersex gonads were observed from the first concentration used (0.01 µg EE2/L) and sexual inversion could be detected from 0.1 µg EE2/L. This was accompanied by a linear decrease in 11-KT levels, whereas no effect on E2 and T levels was observed. Q-PCR results from the gonads showed downregulation of testicular markers (dmrt1, sox9a2; sdY; cyp11b) with increasing EE2 exposure concentrations, and upregulation of the female vtg gene. No evidence was found for a direct involvement of aromatase in the sex conversion process. The results from this study provide evidence that gonads of male trout respond to estrogen exposure by intersex formation and, with increasing concentration, by morphological and physiological conversion to phenotypic ovaries. However, supra-environmental estrogen concentrations are needed to induce these changes.
authors.affiliation: Unit of Research in Environmental and Evolutionary Biology (URBE-NARILIS), Laboratory of Ecophysiology and Ecotoxicology, University of Namur, Namur, Belgium.
authors.forename: Sophie
authors.initials: S
authors.lastname: Depiereux
authors.affiliation: Unit of Research in Environmental and Evolutionary Biology (URBE-NARILIS), Laboratory of Ecophysiology and Ecotoxicology, University of Namur, Namur, Belgium.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Liagre
authors.affiliation: Unit of Research in Environmental and Evolutionary Biology (URBE-NARILIS), Laboratory of Ecophysiology and Ecotoxicology, University of Namur, Namur, Belgium.
authors.forename: Lorraine
authors.initials: L
authors.lastname: Danis
authors.affiliation: Unit of Research in Molecular Biology (URBM-NARILIS), University of Namur, Namur, Belgium.
authors.forename: Bertrand
authors.initials: B
authors.lastname: De Meulder
authors.affiliation: Unit of Research in Molecular Biology (URBM-NARILIS), University of Namur, Namur, Belgium.
authors.forename: Eric
authors.initials: E
authors.lastname: Depiereux
authors.affiliation: Centre for Fish and Wildlife Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Helmut
authors.initials: H
authors.lastname: Segner
authors.affiliation: Unit of Research in Environmental and Evolutionary Biology (URBE-NARILIS), Laboratory of Ecophysiology and Ecotoxicology, University of Namur, Namur, Belgium.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kestemont
mesh_terms: D000818:Animals; D012734:Disorders of Sex Development / Q000139:chemically induced*; D004958:Estradiol / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology; D004997:Ethinyl Estradiol / Q000494:pharmacology*; D005260:Female; D008297:Male; D017686:Oncorhynchus mykiss / Q000502:physiology*; D010053:Ovary / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D012733:Sex Differentiation / Q000187:drug effects* / Q000502:physiology; D013737:Testis / Q000033:anatomy & histology* / Q000187:drug effects / Q000502:physiology; D013739:Testosterone / Q000031:analogs & derivatives / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000494:pharmacology
chemical_list: D004967:Estrogens; D014874:Water Pollutants, Chemical; D013739:Testosterone; D004997:Ethinyl Estradiol; D004958:Estradiol; C003600:11-ketotestosterone