In vitro viability of vitrified mouse morulae thawed at different temperatures.

The effect of thawing temperature on in vitro development of vitrified mouse morulae was investigated. The embryos were vitrified in a solution based on ethylene glycol as cryoprotectant, and Ficoll as macromolecule to assist vitrification. They were then thawed at 20 degrees, 37 degrees and 48 degrees C for 6 sec and at 48 degrees C for 2 sec. Among groups, there was no significant difference on the development at 72 h of culture when embryos were thawed at 20 degrees, 37 degrees C for 6 sec or 48 degrees C for 2 sec. At 48 h of culture the embryos thawed at lower temperature had a reduced resumption (69.5%) while the embryos thawed at 37 degrees and 48 degrees C for 2 sec had a higher resumption rate (80.0% and 82.5%). It was concluded that a high development in vitro of vitrified mouse morulae can be obtained at three different temperatures of thawing, although at higher temperatures there seems to be a tendency of an earlier resumption development.