Interaction of estrogenic alkylphenols and tamoxifen in Fundulus heteroclitus embryos and larvae

Alkylphenols, such as nonylphenol (NP) and octylphenol (OP), have been identified in the aquatic environment and are considered estrogenic. Previously, we reported that NP and 4-tert-octylphenol (4-tOP) were embryotoxic to Fundulus heteroclitus, an estuarine teleost. Here we report that tamoxifen, an estrogen receptor antagonist, can rescue embryos in lethal concentrations of NP and 4-tOP and that this rescue effect is more pronounced with NP. While the embryos coexposed to tamoxifen survive, sublethal abnormalities are still evident. Further studies evaluating hatch success and subsequent larval behavior have shown that these endpoints are also adversely affected by alkylphenol exposure and that tamoxifen does not appear to alleviate the effects on these endpoints. Larval exposure to the alkylphenols demonstrates that NP and 4-tOP are lethal to larvae at concentrations at least an order of magnitude less than those that are embryo-lethal. The relationship between specific sublethal embryonic abnormalities and hatch success is being evaluated. Additionally, current studies are evaluating the effect of chronic low-dose exposure of NP to Fundulus larvae.