Follicular dynamics and apoptosis following unilateral oophorectomy

Ovarian physiology has been based on the assumption that the mammalian ovary has a constant germ cell pool. According to this accepted doctrine primordial follicles, which are limited in number, are depleted through ovulation or atresia. Therefore, the primary goal of this study was to examine the follicle dynamics and morphologic apoptotic changes following unilateral oophorectomy. In order to evaluate the short-, mid-, and long term effects of unilateral oophorectomy, three groups of rats were included in the study. One ovary was removed from each rat on day 0 and used as a control. In group A (n=7), the remaining ovaries were removed via relaparatomy on the 7th day, group B (n=8), the remaining ovaries were removed via relaparatomy on the 14th day, and group C (n=8), the remaining ovaries were removed via relaparatomy on the 42nd day. The changes in the number of primordial, primary, and growing follicles and the difference in apoptotic index were assessed. Even after 10-12 oestrus cycles (in group C) following unilateral oophorectomy, follicle reserve did not show a decrease in the remaining ovary. However, within the growing follicle the ovulatory rate increased. Atretic follicles were elevated contrary to the belief that reproductive functions are compensated as a result of the reduction in atresia. The observations suggest that the number of primordial follicles remains relatively constant.