Background: Leukemia inhibitory factor (LIF) is a 45-56 kDa glycoprotein that has an important role in proliferation and embryo implantation. Its effect on oocyte maturation and how to exert the function remained to be elucidated. Methods: Immature mice superovulated with human menopausal gonadotropin and germinal vesicle (GV) oocytes were obtained from ovary 48 hours after. GV oocytes were cul...