Effects of various cryoprotective agents on the survival of unfrozen and frozen mouse embryos.

The effects of DMSO, ethylene glycol, glycerol, erythritol, dimethylformamide and sucrose on the survival of unfrozen and frozen mouse morulae were examined. All the agents had a deleterious effect on survival of the unfrozen morulae at 20 degrees C. The harmful effect of erythritol was lower at 0 degrees C and sucrose had a protective effect at that temperature. Dimethylformamide and DMSO were more harmful than ethylene glycol and glycerol at both temperatures. Higher proportions of the morulae frozen in DMSO developed into expanded blastocysts when slowly frozen samples were thawed slowly (82%) than when they were thawed rapidly (85%) than when they were thawed slowly (4%). When the samples were frozen in the presence of ethylene glycol or glycerol, higher survival rates were obtained after slow (80--94%) than rapid (1--59%) freezing. When erythritol was used, only embryos thawed rapidly developed (31--50%) in subsequent cultures. Sucrose and dimethylformamide did not afford cryoprotection. Morulae frozen--thawed rapidly in the presence of ethylene glycol, glycerol or erythritol and transferred to recipients developed into normal young.