Androgen action on hepatic vitellogenin synthesis in the eel, Anguilla japonica is suppressed by an androgen receptor antagonist

Involvement of additional hormones other than estrogen in the control of vitellogenin (Vg) synthesis has been suggested in fish. However, no satisfactory explanation on the mechanism of the action of these hormones has been reported. In this study, we have exploited the possibility of androgen receptor mediation during the androgen action on the pathway of Vg synthesis. Hepatocytes were prepared from sexually immature Japanese eel Anguilla japonica and treated with estradiol-17β (E2), 17α-methyltestosterone (MT), growth hormone, tamoxifen or flutamide, or in combination of these. Spent culture media were analysed by SDS-PAGE for Vg detection. Results from the chemical treatments demonstrated the necessity of E2 as the primary factor for Vg synthesis and requirement of additional hormones for the full expression of Vg. The effects of E2 and MT were effectively blocked by tamoxifen, an estrogen receptor antagonist and flutamide, an androgen receptor antagonist, respectively, indicating ER-mediated estrogen action and AR-mediated androgen action on Vg synthesis in this species.