Effects of Epidermal Growth Factor, Insulin Like Growth Factor-I and Insulin on Meiotic Maturation of Bovine Denuded Oocytes

This study was carried out to examine whether EGF, IGF-I and insulin could directly modify the meiotic maturation of bovine denuded oocytes in vitro, and to see whether the stimulatory effect of EGF on bovine oocyte meiotic maturation is mediated through the tyrosine kinase pathway. In the first three experiments, cumulus-oocyte complexes (COCs) were removed from their cumulus cells and the denuded oocytes were cultured in vitro with various concentrations of EGF, IGF-1 and insulin. Nuclear maturation was examined after 24 h of culture. EGF, IGF-1 as well as insulin effectively increased the proportion of oocytes developed to the metaphase II stage. The higher rates of MII oocytes were achieved with 50 ng/ml EGF (69.4%), 100 ng/ml IGF-1 (66.1%) or 5 μg/ml insulin (63.1%) compared to about 48 to 54% in the controls. In experiment 4, whereas EGF significantly (p