Early life-stage mortality in zebrafish (Danio rerio) following maternal exposure to polychlorinated biphenyls and estrogen

In the present study, specific polychlorinated biphenyl (PCB) congeners wer e examined far embryo and early life stage mortality in zebrafish (Danio re rio). A set of eight PCBs and two hydroxylated PCBs and 17 beta-estradiol w ere tested. Of the compounds tested, 4'-OH-PCB30 (hydroxylated polychlorina ted biphenyl) and PCB 104 were found to be highly toxic to embryos followin g maternal exposure and transfer to the oocyte. It was also observed that 1 7 beta-estradiol exposure resulted in a high incidence of embryo mortality. Analysis of estrogen receptor levels during embryonic development showed i ncreased mRNA (ribonucleic acid) levels from the 1K stage to 50% epiboly. F ollowing injection of the different compounds, the estrogen receptor mRNA l evels were also analyzed in adult male fish to determine if there was a cor relation between embryo mortality and estrogenicity of the studied PCBs. Th e two PCBs that were highly embryo toxic were observed to be estrogenic.