Ovarian prostaglandin synthase: immunohistochemical localization in the rat

Ovarian prostaglandin synthase is stimulated by the luteinizing hormone surge resulting in the preovulatory increase in prostaglandins. In the present study, the ovarian cellular localization of prostaglandin synthase was identified by immunohistochemistry. Ovaries were collected from 27-day-old rats at the time of stimulation with pregnant mare serum gonadotropin (8 IU) (zero hours), 48 hours later, or 8 hours after administration of human chorionic gonadotropin (5 IU). At zero hours prostaglandin synthase immunostaining was present in the theca of larger follicles and interstitial regions. The number and intensity of immunostained cells in the theca increased between zero and 48 hours. The granulosa cell layer adjacent to the basement membrane in large antral follicles exhibited immunostaining. A similar staining pattern was observed 8 hours after human chorionic gonadotropin. These observations indicate that in the rat, the theca, interstitium, and granulosa contain prostaglandin synthase immunoreactivity and may contribute prostaglandins during follicular development and ovulation.