title: Vitellogenin induction by a mixture of steroidal estrogens in freshwater fishes and relevant risk assessment.
abstract: The study method on combined effects of environmental contaminant mixture and ecological risk assessment was discussed. Batch tests were conducted to assess the in vivo potency of binary mixtures of estrogens using plasma vitellogenin concentrations in male crucian carp as the endpoint. The estrogenic potencies of 17beta-estradiol (E(2)) and 17alpha-ethynylestradiol (EE(2)) were determined following 14 day exposure to the individual chemicals and equipotent binary mixtures. A Nonlinear regression was obtained and 95% confidence limits of effect concentration were achieved using the bootstrap method. Concentration-response curve for fixed ratio binary mixtures of E(2) and EE(2) was compared with those for individual chemicals, using the biomathematical models of concentration addition (CA) and independent action (IA). A complete overlap was found for the CA predictions with the 95% confidence interval of the best-fit regression line of the observed responses, and the IA predictions was shown lower than the observations. The observed mixture effects were considerably higher than those of the hormone alone and far exceeded the 95% confidence interval of the estrogen regression lines. The predicted effects of binary mixtures at different mixture ratios indicated that the potential impact of components on mixture would depend predominantly on its concentration, the mixture ratio and its relative potency. Results suggested that E(2) and EE(2) acted together in an additive manner and the combined effects can be accurately predicted in whole range of exposure concentration by the models of CA and IA, the model of CA might be realistic, but more useful for ecological risk assessment.
authors.affiliation: Department of Occupational and Environmental Hygiene, School of Public Health, Southeast University, Nanjing 210009, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Fan-Xiang
authors.initials: FX
authors.lastname: Kong
authors.forename: Shi-He
authors.initials: SH
authors.lastname: Wang
authors.forename: Yang
authors.initials: Y
authors.lastname: Yu
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D052244:Endocrine Disruptors / Q000633:toxicity*; D004958:Estradiol / Q000032:analysis / Q000633:toxicity; D004967:Estrogens / Q000032:analysis / Q000633:toxicity*; D005003:Ethisterone / Q000032:analysis / Q000633:toxicity; D005618:Fresh Water / Q000737:chemistry; D006054:Goldfish / Q000097:blood*; D008297:Male; D018570:Risk Assessment; D014819:Vitellogenins / Q000097:blood*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D052244:Endocrine Disruptors; D004967:Estrogens; D014819:Vitellogenins; D014874:Water Pollutants, Chemical; D004958:Estradiol; D005003:Ethisterone