Superovulation of mice with human menopausal gonadotropin or pure follicle-stimulating hormone in combination with human chorionic gonadotropin and the effects of oocyte aging on in vitro fertilization

The response of female mice of F₁ hybrids (CBA×C57/BL) to superovulatory doses of human menopausal gonadotropin (hMG) or pure follicle-stimulating hormone (FSH) in combination with human chorionic gonadotropin (hCG) was studied. Furthermore, the effect of oocyte aging in vivo on the subsequent rate of fertilization in vitro was also investigated. The oocytes were collected at 12, 18, and 24 hr after hCG injection and in vitro fertilization (IVF) was carried out in T6 medium. A higher proportion of animals responded to hMG stimulation (32/70) compared to pure FSH (15/66). Furthermore, hMG gave a higher oocyte recovery (454/32) than pure FSH (77/15). Fertilization rates of 57.8, 51.5, and 53.5% were obtained for the 12-, 18-, and 24-hr groups, respectively, after correction for parthenogenetic division of oocytes in the controls. No significant differences in fertilization rates were observed among the three time intervals used in recovering oocytes. However, as the degeneration and parthenogenetic division increased with the delay in collection of oocytes, 12 hr post-hCG injection was the best time to collect oocytes to obtain optimum results in in vitro fertilization.