The relationship between ovarian progesterone and proteolytic enzyme activity during ovulation in the gonadotropin-treated immature rat.

To clarify the mechanisms by which progesterone acts as a mediator in the ovulatory process, ovulation rate and proteolytic enzyme activities were investigated in immature 22-day-old rats treated with PMSG/hCG, RU486 (10 mg/kg), synthetic antiprogesterone, and RU486 (10 mg/kg)+progesterone (10 mg/kg). The number of ova was significantly decreased when RU486(10 mg/kg) was given from 2 h before to 4 h after the hCG injection. In addition, its inhibitory action on ovulation was reversed by exogenous progesterone (10 mg/kg) at 2 or 4 h after the hCG injection