Comparison of 1,2-propanediol and ethylene glycol for cryopreservation of slow-cooled mouse zygotes and their subsequent development.

PURPOSE: This study was conducted on cryoprotective activity of ethylene glycol (ETG) and propanediol (PROH) on cleavage rate of mouse zygotes. METHODS: Mouse oocytes were excised from fallopian tube of gonadotropin-treated mice, then inseminated with spermatozoa. After 16.5-17.5 h, zygotes were randomly allocated into three groups; control, toxicity, and frozen. In the latter, zygotes were slowly cooled with ETG and PROH similar to those used for human embryo cryopreservation. The survived zygotes cultured for 120 h and their later stages of development were compared with nonfrozen embryos. RESULTS: The toxicity test showed that no differences were observed in cleavage rate between exposed and nonexposed embryos. The survival and expanded hatching blastocyst rate of embryos frozen with PROH was significantly better than with ETG (92.8 vs. 58.2% and 68.2 vs. 39.1%, respectively). CONCLUSIONS: ETG does not appear to be a good alternative to the classical PROH for freezing of mouse zygotes.