Abstract
The in vitro effects of 17, 20β-dihydroxy-4-pregnen-3-one (DHP) and prostaglandins (PGE1, PGE2, PGF1α, PGF2α) on ovulation in the Japanese eel Anguilla japonica were examined. Oocytes with follicle layers at the migratory nucleus stage (approximately 850-900 μm diameter) were removed using a polyethylene cannula from artificially matured fish. At concentrations of 10 and 100 ng/mL, DHP was found to induce both germinal vesicle breakdown and ovulation. The prostaglandins, except for PGE1, effectively inducedovulation of previously matured oocytes by DHP treatment in vitro. Prostaglandin F2α was the most effective. A significant increase in ovulation rate was observed even at a concentration of 0.01 μg/mL PGF2α. Indomethacin blocked the in vitro ovulation induced by DHPand addition of PGF2α reversed indomethacin-blocked ovulation. Actinomycin D and cycloheximide blocked DHP-induced ovulation and PGF2α reversed the effects of both inhibitors. These results indicate that DHP induces ovulation through endogenous prostaglandin synthesis in the follicle layers of the Japanese eel.
