A Study on the Estrus Cycle and Superovulation of the Mouse

Abstract

Pregnant Mare's Serum Gonadotropin (PMSG) has been used for superovulation in animal models by similar techniques used in human in vitro fertilization and embryo transfer (lVF & ET). Intraperitoneal injection of PMSG and human chorionic gonadotropin (HCG) 48 hours apart will result in ovulation approximately 14 to 19 hours later. The number of oocytes ovulated is affected by age, strain, dose of gonadotropin, timing of injections, and environmental factors. This study was undertaken to evaluate the effect of estrus cycle on the retrieval of mouse oocytes in conjunction with mouse in vitro fertilization as a quality control testing for Seoul IVF & ET program. Vaginal smears were made by lavage of the vagina with saline solution using an eyedropper. We observed the cell types on the Papanicolaou stained smear to confirm the stage of the mouse estrus cycle. Superovulation was induced with intraperitoneal injection of 5.0 I.U. PMSG followed by 5.0 l.U. HCG 48 hours later. Oocytes retrieval was done 16 hours after the intraperitoneal injection of HCG. Oocytes retrieval rates according to the stage of estrus cycle were 14.9±2.6 in proestrus stage(N=16), 15.8±3.4 in estrus stage(N=24), 15.7±3.8 in metestrus stage(N=16), and 15.1 ±4.6 in diestrus stage(N = 18). These results revealed that the stage of estrus cycle in mice did not affect the oocyte retrieval rate.