Effect of indomethacin, cycloheximide, aminoglutethimide on ovarian steroid and prostanoid levels during ovulation in the gonadotropin-primed immature rat

It has become popular to use the gonadotropin-primed immature rat to study ovulation. The ovarian content of progesterone, estradiol, PGE2, PGF2 alpha, and 6-keto-PGF1 alpha during the ovulatory process was determined in this model. Also, the effect of three anti-ovulatory agents on the ovarian levels of the above substances was determined. At 23 days of age, Wistar rats were primed with pregnant mares serum gonadotropin (PMSG) sc, and two days later the ovulatory process was initiated with human chorionic gonadotropin (hCG) sc. The ovarian follicles began rupturing 12 h later. Ovaries were assayed for the two steroids and prostanoids at 2-h intervals before and several 4-h intervals after ovulation. The ovarian estradiol level increased slightly between 0 and 2 h after hCG, while the progesterone level increased sharply between 2 and 4 h after hCG--at a time when the estradiol declined markedly. All three prostanoids increased concomitantly with progesterone. When the PG synthesis was blocked by indomethacin treatment at 1 h before hCG, ovarian progesterone levels still increased. In contrast, when steroidogenic activity was inhibited by aminoglutethimide, the ovarian prostanoid levels also decreased. Cycloheximide had little effect on the steroids and prostanoids. It is concluded that ovarian prostanoid synthesis might be influenced by ovarian steroid output.