RU486 inhibits ovulation, fertilization and early embryonic development in rabbits: in vivo and in vitro studies

Objective: To clarify the role of P in ovulation, fertilization, and early embryonic development using RU486, a potent P receptor blocker.Design: Ovulatory efficiency, IVF, and early embryonic development were evaluated after RU486 administration in vivo and in vitro.Setting: Research laboratory of a university hospital.Participants: Mature male and female New Zealand white rabbits.Interventions: Animals were treated with RU486 or vehicle for 3 days before hCG-induced ovulation. Ovaries treated with hCG to induce ovulation were perfused for 6 hours in vitro with RU486 or vehicle. In vitro fertilization was performed in the presence or absence of RU486.Main Outcome Measures: The percentage of mature follicles ovulating (ovulatory efficiency) was determined after in vivo and in vitro treatment. Fertilization, morula, and blastocyst development were evaluated every 24 hours for 120 hours.Results: RU486 significantly inhibited ovulation, fertilization, and early embryonic development.Conclusions: Progesterone plays a significant role in ovulation, fertilization, and preimplantation embryonic development.