Fentress, J.A.*; Brouwer, T.H.; Brouwer, M.; McLachlan, J.A.; Cheek, A.O.: Examination of a potential environmental anti-estrogen

Anthracene, a polyaromatic hydrocarbon, has been shown to induce anti-estrogenic effects in fish. In the medaka, Oryzias latipes, short term exposure to 12 or 20ug/ml anthracene (ANT) blocks estrogen induced feminization, while long term exposure leads to reduced fertility and hatching success. To determine if anthracene is an estrogen receptor antagonist, we measured vitellogenin (VTG) production in response to estradiol (E2) +/- anthracene. VTG serves as a natural reporter gene for estrogen receptor activation. We exposed fry for 2 or 8 weeks post hatch to one of the following treatments: water, solvent, 1 nM E2, 12 ug/ml ANT, 20 ug/ml ANT, 1nM E2 + 12 ug/ml ANT, or 1nM E2 + 20 ug/ml ANT. Fish were sub-sampled at 2, 4, and 8 weeks post hatch for VTG analysis. Vitellogenin was analyzed using Western blots and quantified by densitometry. Fry exposed to estrogen for 2 weeks and sampled at 2 weeks produced VTG, while fish sampled at 4 and 8 weeks showed an attenuated response to estrogen. Fish exposed to estrogen for 8 weeks produced VTG throughout the exposure period. When exposed to ANT alone fish did not produce VTG. Regardless of dose or exposure duration, ANT did not prevent the production of vitellogenin in co-exposed fish. Because anthracene was unable to block the production of vitellogenin, it is unlikely that its anti-estrogenic effects are mediated through the E2 receptor.