The protective action of glycols against freezing damage of mouse and rat embryos.

Eight-cell mouse and rat embryos were frozen to -79 degrees C or -196 degrees C in the presence of ethylene, diethylene, triethylene, propylene or polyethylene glycol. Ethylene glycol was the most effective cryoprotectant for mouse and rat embryos and considerable protection against damage during freezing and thawing was also afforded by propylene glycol. The degree of protection given by the other glycols was relatively low. Mouse embryos survived freezing after only 0.1 min exposure to ethylene glycol at 0 degrees C but exposure for longer periods was necessary with the other glycols. Mouse embryos that survived freezing and thawing with a glycol as the protective agent were capable of developing to full-term fetuses.