In this study we aimed to investigate the distribution and expression level of pro and anti-apoptotic proteins, Bax and Bcl-2, in different developmental stages of ovarian follicles and any relations between these proteins and follicle atresia. Materials and Methods: For that purpose, bilateral 16 ovaries of adult 8 mice were received and the tissues were fixed in 10% neutral buffered formalin. Routine tissue processing protocol was performed and the samples were embedded into paraffin blocks.

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... ive µm thick sections were received and the tissue sections were stained with Bax and Bcl-2 immunohistochemistry. The ovarian follicles were classified as primordial, primary, secondary and antral. Distribution and expression levels of Bax and Bcl-2 were evaluated among and within the developmental stages. The expression levels of Bax and Bcl-2 were also compared with atretic follicle ratio. Results: Immunopositivity of Bax and Bcl-2 were observed in ovarian stromal cells, granulosa, oocytes, and lutheal cells in a varying range. Despite of some immunpositivity, most of the primordial and primary follicle granulosa cells and oocytes were negative for these apoptosis regulator proteins. The intensity of immunopositivity increased at the farther developmental process in follicles. In addition, the immunoexpression level significantly increased just with the beginning of the secondary follicular stage and the expression levels were the most intense in antral follicles. Furthermore, some of the antral follicles were intense Bax positive which were observed with atretic follicle morphology. Conclusions: Bax and Bcl-2 are crucial regulators in ovarian follicle development. Although Bcl-2 contributes on follicular development, correlation analyses of this study indicated that Bax is a stronger decision marker than Bcl-2 for the fate of ovarian follicle.