Study Of Combination Effects Of Environmental Estrogens And Antiestrogens On Zebrafish (Danio Rerio) Embryos

At present the most study of research in endocrine disrupting chemicals (EDCs) are study of compound effect of the same kind of EDCs. Study of different kinds need to be strengthen. In this study, after exposure to the typical estrogen 17β-estradiol(E2), o,p'-DDT and antiestrogen tamoxifen(TAM), fulvestrant, morphology levels of toxicological endpoints of zebrafish (Danio rerio) embryos such as hatching rate, hatching time and gross abnormalities rate were observed. Then real-time quantitative PCR was used to investigate the changes in transcription of mRNA of estrogen-responsive gene such as VTG1, VTG2 and ERα. The combined effects between the four EDCs were analyzed and evaluated to provide a scientific basis for comprehensive understanding the combination effects between estrogen and antiestrogen. The major findings are as follows:(1) Single EDCs impacted morphology of zebrafish embryos. Expression of VTG gene was increased because of estrogen inducing. Expression of ERαgene was inhibited by fulvestrant. TAM showed a weak estrogenic effect.(2) At morphological level in embryonic development, reproductive toxicity in mixtures did not decrease because of interactions between antiestrogen and estrogen,which was different from the traditional view. In addition, compared to the gross abnormalities rate and the hatching rate, the hatching time of embryos did not reflect well the compound effect.(3) At the level of gene transcription, estrogen and antiestrogen in the binary mixtures generally showed a antagonistic effect, which meant the antiestrogen reduced the effects of estrogen. But in the binary mixtures of o,p'-DDT and TAM, high concentrations of TAM showed a weak estrogen effects and did not showed obvious antagonistic effect to o,p'-DDT.It could be indicated from the findings that antiestrogen did not simply inhibit the ecotoxicological effects of estrogen. So we should evaluate the combination effects of estrogens and antiestrogens comprehensively when conduct ecological risk assessment.