title: Relationship between ethinylestradiol-mediated changes in endocrine function and reproductive impairment in Japanese medaka (Oryzias latipes).
abstract: Many biochemical endpoints currently are used to describe endocrine function in fish; however, the sensitivity of these parameters as biomarkers of impaired reproduction or sexual development is not well understood. In the present study, adult Japanese medaka (Oryzias latipes) were assessed for reproductive output and endocrine function, including circulating steroid concentrations, ex vivo steroidogenesis from the gonads, aromatase activity, hepatic estrogen receptor (ER), and plasma vitellogenin (VTG) after exposure to 0, 0.2, 5, 500, and 2,000 ng/L of 17alpha-ethinylestradiol (EE) for 14 d. The EE altered these biochemical responses at various sites along the hypothalamus-pituitary-gonadal axis at concentrations as low as 0.2 ng/L, but it only depressed reproductive function at concentrations of 500 ng/L or greater. Offspring also had reduced ability to hatch at 500 ng/L of EE, but this concentration did not produce any other observed changes in development or sexual phenotype. The reproductive parameters correlated well with VTG, ER, and gonadosomatic index (GSI) in both sexes of adult medaka, which could be indicative of the ER-mediated mode of action for EE. Vitellogenin and ER were elevated at higher concentrations of EE in both sexes, whereas GSI was decreased. Overall, most biochemical endpoints were more sensitive than reproduction or development to exposure, indicating that reproductive function may be relatively protected.
authors.affiliation: Environmental Toxicology Research Program, University of Mississippi, University, Mississippi 38677, USA.
authors.forename: Susan C
authors.initials: SC
authors.lastname: Tilton
authors.forename: Christy M
authors.initials: CM
authors.lastname: Foran
authors.forename: William H
authors.initials: WH
authors.lastname: Benson
mesh_terms: D000818:Animals; D001141:Aromatase / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004703:Endocrine System / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism / Q000502:physiology; D004997:Ethinyl Estradiol / Q000097:blood / Q000378:metabolism / Q000633:toxicity*; D005260:Female; D006062:Gonadotropins / Q000378:metabolism; D006066:Gonads / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018811:Maternal Exposure; D009641:Norethynodrel / Q000031:analogs & derivatives*; D009990:Oryzias; D010063:Ovum / Q000187:drug effects; D010641:Phenotype; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism; D012098:Reproduction / Q000187:drug effects* / Q000502:physiology; D012737:Sex Factors; D014819:Vitellogenins / Q000097:blood / Q000187:drug effects / Q000378:metabolism
chemical_list: D006062:Gonadotropins; D011960:Receptors, Estrogen; D014819:Vitellogenins; C002029:17alpha-ethynylestr-5(10)-ene-3alpha,17beta-diol; D004997:Ethinyl Estradiol; D009641:Norethynodrel; D001141:Aromatase