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Effects of anti-progesterone compound RU486 on ovulation in immature mice treated with PMSG/hCG
K Kanayama1, T Sankai, K Nariai
1Department of Veterinary Medicine, College of Agriculture and Veterinary Medicine, Nihon University, Kanagawa, Japan.
Abstract:
The effects of RU486, a competitive antagonist of progesterone, on ovulation were studied in PMSG/hCG-treated immature mice. PMSG/hCG was administered to 3-week-old female mice to induce ovulation. A dose of 0.5 mg of RU486 was administered 3 h before hCG injection, simultaneously with hCG injection, or 3, 4.5, 6, 7.5 or 9 h after hCG administration. The lowest number of ovulated eggs was observed in the group given RU486 6 h after hCG injection. Although the mean number of ovulated eggs was only 4.4 in this group, it was increased to 25.7 by supplementary administration of 2.0 mg of progesterone. It was demonstrated that RU486 had inhibitory effects on ovulation, and the inhibition could be prevented by supplementary administration of progesterone.
Insights
The drug RU486 (mifepristone) inhibits ovulation in mice, but this effect can be reversed by administering progesterone. This highlights progesterone
Area of Science:
- Reproductive Endocrinology
- Pharmacology
Background:
- Ovulation is a complex process regulated by hormonal signals.
- Progesterone plays a critical role in the ovulatory cascade.
- RU486 is a progesterone receptor antagonist.
Purpose of the Study:
- To investigate the effects of RU486 on ovulation in a mouse model.
- To determine the timing and reversibility of RU486-induced ovulation inhibition.
Main Methods:
- Immature female mice were treated with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) to induce ovulation.
- RU486 was administered at various time points relative to hCG injection.
- The number of ovulated eggs was quantified.
- Progesterone was administered as a supplementary treatment.
Main Results:
- RU486 administration inhibited ovulation, with the most significant effect observed when given 6 hours after hCG.
- The mean number of ovulated eggs decreased significantly in the presence of RU486.
- Supplementary progesterone administration successfully reversed the inhibitory effects of RU486 on ovulation.
Conclusions:
- RU486 exhibits inhibitory effects on the ovulation process in PMSG/hCG-treated mice.
- The timing of RU486 administration is crucial for its inhibitory impact.
- Progesterone can counteract the anti-ovulatory effects of RU486, underscoring the importance of progesterone in ovulation.