Antagonistic Estrogenic Effects Displayed by Bisphenol AF and Perfluorooctanoic Acid on Zebrafish (Danio rerio) at an Early Developmental Stage

Bisphenol AF (BPAF) and perfluorooctanoic acid (PFOA) may display combined estrogenic effects on aquatic organisms, because BPAF and PFOA are widely present in the aquatic environment and reported to have estrogenic effects on aquatic organisms. In this study, zebrafish embryos were exposed to BPAF, PFOA, and binary mixtures of both for 7 days using estradiol (E2) and vitellogenin (VTG) as biomarkers. The estrogen receptor alpha (er alpha) expression and VTG level increased upon single exposures to BPAF (0.0372 and 0.372 mu M) and PFOA (1.21 and 12.1 mu M). Although both of them stimulated the P450 aromatase level, they displayed opposite effects on sex hormone-binding globulin. As a result, BPAF stimulated the E2 level but PFOA depressed it, and an antagonist effect on the E2 level was observed in the binary mixtures. The significant correlation between VTG level and er alpha expression suggested er alpha played a vital role in VTG synthesis. BPAF and PFOA could compete for the key common residue, Arg362, in the binding pocket of ER alpha, inducing antagonistic effects on er alpha-driven transcriptions. Thus, BPAF and PFOA displayed an antagonistic estrogenic effect on zebrafish during an early development stage.