Abstract
Mouse oocytes were induced to mature by injecting with pregnant mare serum gonadotropin and human chorionic gonadotropin, and the c-fos protein accumulated in the oocytes was detected by immunohistochemical method. Intense/very intense staining was observed with monoclonal antibodies against the c-fos protein in maturing oocytes and cumulus cells in Graafian follicles, but slight/moderate staining in oocytes with germinal vesicle in antral follicles; the most intensive signal was observed in oocytes which induced germinal vesicle breakdown in Graafian follicles at 6 h after hCG administration. Immunoreactions associated with cellular compartments of the oocyte cytoplasm was identified under the electron microscope. The c-fos protein was also detected in the matured oocytes in the oviduct, although the intensity decreased gradually after ovulation. Positive immunostaining was not detected in granulosa and theca layers, and interstitial connective tissue, confirming that the expression of the c-fos protein is elevated particularly in the maturing oocytes in the ovary.
