Gamma-radiation accelerates ovarian follicular atresia in immature mice

This study deals with the morphological degenerations of normal and atretic follicles based on artificially induced radiation apoptosis. ICR strain of 3 week-old female mice were whole body irradiated with 8.3 Gy and sacrificed by cervical dislocation. Ovaries were collected at 0 h, 6 h, 12 h, 1 d, 2 d, 4 d, and 8 d post irradiation and processed for morphological observation. Irradiated ovarian follicles showed such characteristics as faint connection between zona and cumulus thinning of granulosa layer, numerous apoptotic bodies, and increased cell debris in antrum. However, in normal ovaries about a half of the follicles were healthy. Within 6 h post irradiation, more than 95% of follicles steeply became apoptotic. At 4 d, severely damaged follicles with hypertrophed theca layer and fragmented oocytes were shown. At 8 d, normal shaped follicles were observed together with severely disrupted ones. The normal shaped follicles seemed to have grown from radioresistant ones. In conclusion, gamma-radiation had an additive or concomitant effect on atretic degeneration of mouse ovarian follicles.