One hundred and six Swiss Albin CF1 mouse morulae were frozen by ultra rapid method. The embryos were colected 76-78h after HCG administration and the freezing was done in glycerol 2.0M + sucrose 0.25M (Group S) or in glycerol 2,0M + lactose 0,25M (Group L), both in Modified Dulbecco' s Phosphate Buffered Saline (PBS). Firstly, the embryos were placed in a equilibration medium containing 2.0M glycerol for 4 minutes after which the morulae were transfered to a freezing solution for 1 minute. The embryos were loaded in groups of 5 to 11 in 0.25ml plastic straws. These straws were maintained for 2 minutes in nitrogen vapour and then plunged into liquid nitrogen. After thawing at 37°C for 20 seconds, one hundred and three morulae were recovered. The cryoprotectant was diluted in 0.5M sucrose solution (Group S) or 0.5M lactose solution (Group L), for 5 minutes at room temperature. After three baths in PBS the viable embryos were cultured in Modified PBS at 37°C, for 44-48h. Through morphological evaluation, 45 (86.5%) and 46 (90.2%) morulae were considered viable after the cryoprotectant dilution in the groups S and L, respectively. The development rate was 67.3% (n=52) with Group S and 64.7% (n=51) with group L. No significant differences (P >0,01) were observed in embryo viability or in survival rate after thawing and culturing, with both sugars.
embryo freezing; sucrose; lactose
