Rescue of Atretic Follicles in Vitro and in Vivo1

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Abstract
The purpose of this work was to determine if atretic follicles could be rescued and could return to the ovulatory pathway of development. Rats were given continuous infusion of 3H-thymidine (3H-TdR) resulting in uniform labeling of healthy antral follicles versus patchy labeling of atretic antral follicles. The infusion was then stopped and rats were subjected to experimental treatments known to stimulate follicular recruitment. Immature rats were given injections of pregnant mare''s serum gonadotropin (PMSG) to provoke superovulation. Adult rats were hemicastrated to provoke compensatory follicular development in the remaining ovary. In addition, granulosa cells from individual follicles of adult rats were cultured in vitro. The differential labeling patterns, observed at the end of the treatment period, were used to determine, a posteriori, the condition of follicles as they had been at the start of the treatment period. Sparsely labeled cell cultures were found, indicating that some cells from atretic follicles were able to become established in tissue culture. However, there was no evidence that atretic follicles had revived in vivo. All follicles recruited for ovulation by PMSG or hemicastration were heavily and uniformly labeled. All poorly labeled follicles were clearly continuing their process of degeneration. These observations suggest that, despite continued viability of some granulosa cells in atretic follicles, once a follicle begins to degenerate in vivo, it will probably not return to the ovulatory pathway.