Estrogenic activity of nonylphenol in marine fish, Hexagrammos otakii, during oocyte development by evaluating sex steroid levels

In this study, we examined the potential estrogenic activity of nonylphenol (NP) on oocyte development of a marine fish, Hexagrammos otakii, using steroid hormone assays. Vitellogenic (0.80-82, 0.92-96 and 1.08-12 mm diameter) and fully matured (1.90-95 mm diameter) oocytes were in vitro exposed to NP at different concentrations (0.1, 1, 10 and 100 ng/ml) with or without 50IU human chorionic gonadotropin (HCG). NP increased the estradiol-17 beta (E2)/testosterone (T) ratio at 0.1, 1 and 10 ng/ml in the oocytes of 0.80-82 and 0.92-96 mm. In the oocytes of 1.08-12 mm, which were fully vitellogenic stage, NP increased E2/T ratio only at 100 ng/ml. In the oocytes of 1.90-95 mm, NP increased E2/17 alpha-20 beta-dihydroxy-4-pregnen-3-one(17 alpha 20 beta P) ratio at all concentrations tested without HCG and decreased E2/17 alpha 20 beta P ratio in the presence of HCG but not in a dose-dependent manner. Taken together, these results suggest that NP exhibits estrogenic activity through ovarian development of H. otakii.