The ovulatory gonadotrophin surge stimulates cyclooxygenase expression andprostaglandin production by the monkey follicle

Follicular prostaglandin concentrations increase following the gonadotrophi n surge in domestic animals and rodents similar to 10 h before follicle rup ture, suggesting a unifying role for prostaglandins in the timing of ovulat ion. However, little is known about prostaglandin production by the primate ovulatory follicle. In this study, adult female macaques received gonadotr ophins to promote follicular development. Granulosa cells, follicular fluid , and ovaries were collected before (0 h) and 12, 24 or 36 h after administ ration of the ovulatory stimulus, human chorionic gonadotrophin (HCG). Cycl ooxygenase (COX) isoform expression was assessed by reverse transcription-p olymerase chain reaction and immunocytochemistry and follicular prostagland in production was determined by enzyme immunoassay. COX-2 mRNA expression i n granulosa cells was low at 0 h, rose 50-fold by 12 h, and remained elevat ed through to 36 h. COX-2 immunostaining was present in granulosa cells aft er, but not before, exposure to HCG. COX-1 mRNA levels did not change durin g the periovulatory interval, and COX-1 immunostaining of granulosa cells w as not detected. Follicular fluid prostaglandin (PG) E-2 and PGF(2 alpha), concentrations were low through to 24 h but increased 100-fold at 36 h. The elevated follicular prostaglandin concentrations 4-16 h before the expecte d time of ovulation support the hypothesis that the time between the LH sur ge and increased follicular prostaglandins determines the length of the per iovulatory period. Differences between the localization and timing of COX-2 expression in monkey versus non-primate follicles suggest that the pattern of COX-2 expression and activity has aspects unique to primates.