Effects of tamoxifen, 17α-ethynylestradiol, flutamide, and methyltestosterone on plasma vitellogenin levels of male and female Japanese medaka (Oryzias latipes).

The effects of oral administration of tamoxifen, 17α-ethynylestradiol (EE2), flutamide, and methyltestosterone (MT), on plasma vitellogenin levels of male and female medaka were investigated. Medaka were fed diets containing different concentrations of these chemicals for 7 days, and these plasma vitellogenin levels were measured. Tamoxifen increased significantly the vitellogenin levels in male, but inhibited the normal vitellogenin induction in female in the high concentration groups. EE2 increased significantly vitellogenin levels in both sexes. Flutamide increased significantly the vitellogenin levels in female, but gave no effects on male. MT inhibited the normal vitellogenin induction in female, but increased slightly vitellogenin levels in male without a clear tendency. Administration of tamoxifen, EE2, flutamide, and MT showed the different pattern in vitellogenin levels in both sexes.