PREIMPLANTATION EMBRYO DEVELOPMENT IN ICR MICE AFTER STREPTOZOTOCIN TREATMENT

To investigate the significance of impaired insulin secretion on preim plantation embryo development, outbred ICR female mice received a sing le injection of streptozotocin 130 mg (low) and 160 mg (subdiabetic) k g(-1), 14-17 days before fertilization. Preimplantation embryos were c ollected on day 3 of pregnancy, four to eight-cell embryos were cultur ed in vitro 48 h (day 5) and their cell number was estimated. After sp ontaneous ovulation, the significantly different distribution pattern in comparison with the controls was detected only in preimplantation e mbryos isolated from subdiabetic (160 mg.kg(-1) streptozotocin) mice. Furthermore, the incidence of degenerated embryos was significantly in creased after 48 h in vitro cultivation. The analysis of cell number d istribution in embryos after cultivation irt vitro indicated a signifi cant delay in cell proliferation in both experimental groups (130 and 160 mg.kg(-1) streptozotocin) in comparison with control mice. After s uperovulation, the only significant difference was found in the distri bution pattern of embryos isolated on day 3 of pregnancy from subdiabe tic (160 mg.kg(-1) streptozotocin) mice. No significant differences we re found after embryo cultivation in vitro. It could be concluded that , in outbred ICR mice, lower streptozotocin treatment (130 mg.kg(-1)) influenced only cell distribution of in vitro cultured embryos after s pontaneous ovulation. In ICR mice, marked changes in preimplantation e mbryo development were detected only after subdiabetic (160 mg.kg(-1)) streptozotocin treatment. During in vitro cultivation delayed effects of impaired insulin secretion resulted in an increase of embryo degen eration at the time after the third mitotic cleavage. Our results indi cate that the effects of impaired maternal insulin secretion on preimp lantation embryo development in mice are marked and consistent after s pontaneous ovulation. Superovulation apparently disguises subtle chang es in preimplantation embryo development after low and subdiabetic str eptozotocin treatment.