Immunohistochemical localization of superoxide dismutase in the human ovary

To elucidate the physiological function of superoxide dismutase (SOD) in the ovary, we examined the immunohistochemical distribution of CuZn-SOD in the human ovary. We also measured the CuZn-SOD concentration in human follicular fluid by enzyme-linked immunosorbent assay (ELISA). The germinal epithelium and tunica albuginea showed no or weak immunoreactivity. No or weak staining activity was also observed in the non-antral follicle. Once the follicle began to form the antral cavity, theca interna cells began to show intensive immunostaining of SOD, as compared with no staining in the granulosa and theca externa cells. In the gestational corpus luteum, theca and granulosa lutein cells showed intensive and moderate staining activity, respectively. The concentration of CuZn-SOD was 0.222 +/- 0.186 ng/mg protein (mean +/- SD) in the preovulatory follicular fluid. In the present study, the immunohistochemical distribution of SOD was confirmed in the human ovary for the first time. Taking into consideration the fact that SOD catalyses the dismutation reaction of superoxide anion radicals, the present results suggest that theca interna cells play an important role in the protection of the developing oocyte from oxygen radicals by acting as a blood-follicular barrier during follicle maturation.