The effect of supercooling on the developmental capacity of mouse embryos.

The effect of supercooled storage (at subzero temperatures without ice formation) on compacted mouse morulae and early blastocysts was studied. The embryos were equilibrated with one of three storage solutions containing 1, 3, or 6% each of methanol and glycerol and cooled to -2, -5, -10, or -15 degrees C and stored for up to 24 h to assess the effect of subzero storage at different temperatures and concentrations of the permeating cryoprotectants on embryo survival. Early blastocysts showed substantially greater survival than morulae and, in general, survival of embryos of either stage increased with the concentration of cryoprotectant, while the proportion of embryos surviving decreased with decreasing storage temperature and with increased duration of storage.