Abstract:Objective: Two-cell block as a problem occurs in some couples referring to infertility center. This study was designed to compare the effect of different kinds of chemical activators on arrested mouse two-cell stage embryos in order to enhance cleavage and developmental formation rate. Material and Methods: Following superovulation, the female mice were mated with males and positive vaginal plaque mice were euthanized 48 hours after hCG injection. Subsequently, 2-cell embryos were collected and randomly cultured (in M16 medium) in six groups. Some embryos were washed and cultured as 1st group without any exposure. The remaining 2-cell stage embryos were exposed to 4°C for 24 hours in order to arrest in 2-cell stage for 2nd to 6th groups. The 2nd group was incubated immediately, while the 3rd group was exposed to 10 µM Ionomycine for 3 minutes and the 4th group was exposed to 10 mM strontium for 5 minutes. The 5th group was exposed to %0.1 Ethanol for 5 minutes and the 6th group to %0.1 Methanol for 3 minutes. Subsequently, all groups were incubated up to blastocyst stage. Results: Data were analysed employing a one-way Anova test the results show that the rate of degenerated embryos is significantly different (P<0.05) between groups by low temperature (4°C) exposure. The mean percentages of cleavage, blastocyst and hatched blastocyst formation rate in the 4th group were 80.9%, 69.2%, and 46% respectively, showing a significant difference between groups. Conclusion: This study shows that among different chemical activators used in this study, Strontium is the most powerful chemical activator to enhance cleavage and development of arrested two-cell embryos in the 4 th group.

Abstract-Arresting in a certain step of development, like two-cell stage could be one of the reasons of infertility. In this study, we evaluate the effects of ethanol on growth and development of mouse two-cell arrested embryos. In this xperimental study 4-6 week-old female mice were coupled with males following superovulation by intraperitoneal injection of pregnant mere serum gonadotropin (PMSG). Positive vaginal plug mice were killed 48 hours after human chorionic gonadotropin (hCG) injection. Two-cell embryos were transferred to culture medium, and divided in three groups, 1(control 1), 2 (control 2) and 3 (experimental). Second and third groups were exposed to 4º C for 24 hours in order to arrest the two-cell embryos. Group 2 were incubated immediately in 38º C, while group 3 were exposed to 0.1% ethanol for five minutes and group 1 were incubated without any exposure to low temperature. The developmental rate of embryos exposed to low temperature (4º C) were significantly decreased and retarded (P=0.001). There was no significant difference in the mean percent of cleavage rate between groups, but the mean percent of degenerated embryos (P=0.045), morula formation (P=0.005), blastocyst formation (P=0.014) and hatched blastocyst (P=0.001) in 120 h study, were significantly different between groups. The effect of 0.1% ethanol on arrested two-cell embryos can significantly enhance the mean percent of morula formation and development of blastocysts and hatching blastocysts comparing to 2 nd control group, without any significant effect on cleavage rate.