Indirect immunofluorescence studies on the steroid-producing activity of hamster ova

Steroidogenesis in the unfertilized hamster ova was investigated by indirect immunofluorescence study. delta 5-3 beta-Hydroxysteroid dehydrogenase (delta 5-3 beta-HSD) activity was found in hamster follicular and ovulatory ova with pregnenolone used as the substrate. A significant quantity of 17 beta-estradiol was detected in the ooplasm of follicular and ovulatory ova. No progesterone was found. The activity of delta 5-3 beta-HSD in follicular and ovulatory ova was inhibited by preincubation with 10 IU of human chorionic gonadotropin (hCG) in 1 ml of phosphate buffer solution. Trilostane, a potent new inhibitor of the delta 5-3 beta-HSD system, was found to inhibit the activity of delta 5-3 beta-HSD in ovulatory ova in 1 ml of phosphate buffer solution at a concentration of 10(-7)M. After these results were obtained, steroidogenesis of hamster ova was suggested in an indirect immunofluorescence study, and the implications of steroidogenesis for oocyte maturation and subsequent fertilization are discussed.