HISTOLOGIC AND AUTORADIOGRAPHIC STUDY OF THE IN-VITRO EFFECTS OF FGF-2 AND FSH ON ISOLATED BOVINE PREANTRAL FOLLICLES - PRELIMINARY INVESTIGATION

Bovine early preantral follicles (40 to 65 mu m diameter) were culture d for 24 or 48 h in the presence of 0, 10, 50 or 100 ng/ml of basic fi broblast growth factor (FGF-2), porcine FSH (pFSH) or both (ratio 1:1) ; the follicles were also exposed throughout the entire culture period to 2 mu Ci/ml (H-3) thymidine. The effects of these factors on oocyte morphology and follicular DNA synthesis were then analyzed. Autoradio graphy was performed on histological serial sections of follicles afte r the culture period. Oocyte morphology of each follicle and the rate of follicular DNA synthesis were evaluated at the same time. Oocyte mo rphology was considerably altered in the presence of exogenous FSH. Th is effect seemed to be reduced by FGF-2, at least up to 24 h of cultur e. Analyzable incorporation of (H-3) thymidine was only detected after 48 h of culture. The FGF-2 significantly increased the number of labe led nuclei per follicle whereas pFSH did not. This responsiveness of g ranulosa cells to FGF-2 disappeared in the presence of pFSH. No correl ation was found between the number of labeled nuclei per follicle and the morphology of its oocyte. These results suggest that in cultured b ovine early preantral follicles, pFSH induces oocyte degeneration and that this degeneration seems to be attenuated by FGF-2. In addition, F GF-2 lead to an increase in follicular DNA synthesis that disappeared in the presence of pFSH.