Expression and distribution of cyclooxygenase-2 in human periovulatory ovary

Cyclooxygenase, which converts arachidonic acid into prostaglandins, has two types of isoforms, cyclooxygenase-1 and cyclooxygenase-2 (COX-2). The latter is thought to be essential for the ovulatory mechanism. However, expression or distribution of COX-2 in periovulatory human ovary has not been reported. The aim of our study was to examine COX-2 expression and distribution in pre- and postovulatory human ovary. COX-2 was detected by Western blot analysis of pre-ovulatory human ovarian follicular fluid. The levels of COX-2 in preovulatory fluid obtained from 20 subjects underwent in vitro fertilization and embryo transfer, and were assayed using enzyme immunoassay for human COX-2. The results showed 7.3+/-4.1 ng/ml (mean +/- SD) with a COX-2 level range of 2.7 to 19.5 ng/ml of follicular fluid. Detection of COX-2 is considered to reflect its production in the preovulatory follicle. Immunofluorescence microscopic examination of an ovary obtained from a woman at the postovulatory period showed distribution of COX-2 in interstitial but not in granulosa cells in a ruptured follicle. These findings collectively suggest the possibility that COX-2 is mainly produced in follicles in a preovulatory phase, while after ovulation, COX-2 is produced in interstitial cells in human ovary.