Effects of β-mercaptoethanol and cycloheximide on survival and DNA damage of bovine embryos stored at 4°C for 72h

The objectives of this study were to determine the effects of cycloheximide (CHX) and β-mercaptoethanol (β-ME) during storage of in vitro-produced (IVP) bovine blastocysts for 72h at 4°C on their survival, hatching capacity and DNA damage. In Experiment 1, when blastocysts were stored in a medium supplemented with 25, 50 or 100μg/mL of CHX, or 25, 50 or 100μM of β-ME, the blastocysts stored with 25μg/mL of CHX had a significantly higher survival rate than that of the blastocysts stored without CHX (79.5% versus 54.2%). In contrast, β-ME had no apparent effects on the survival and hatching capacity of stored embryos. In Experiment 2, to investigate synergistic effects of CHX and β-ME during storage of blastocysts on their developmental parameters and DNA damage, they were stored in the medium with CHX (25μg/mL) and β-ME (50μM). The combination of CHX and β-ME had no significant effects on the survival of blastocysts. The proportion (6.8%) of DNA-fragmented cells in the blastocysts stored with CHX was similar to that (5.4%) in the non-stored blastocysts (positive control) and significantly lower than that (9.7%) in the blastocysts stored without CHX and β-ME (negative control). However, there were no significant differences among the proportions of dead cells of blastocysts in the storage groups. Therefore, the supplementation of CHX in the storage medium had a beneficial effect on the proportions of survival and DNA-fragmented cells in the stored embryos, whereas the β-ME alone or in combination with CHX had no positive effects on either of these proportions.