Critical cooling and warming rates to avoid ice crystallization in small pieces of mammalian organs permeated with cryoprotective agents.

Measurements were made by differential scanning calorimetry on small pieces of rabbit kidney permeated with 2, 3-butanediol containing mainly the levo- and dextro-isomers. The critical cooling rates necessary to vitrify the pieces of organ, and the corresponding critical warming rates which are required to avoid crystallization in the vitrified samples, were determined. The dynamic method used for these determinations is described. The glass-forming tendency and the stability of the amorphous state were both greater in the kidney tissue samples than in the bulk cryoprotective solution. This result is discussed in the context of the lowering of the freezing point of water in emulsions and the promotion of supercooling in hydrogels and porous materials. In corresponding experiments with rat hearts impregnated with 1,2-propanediol, only the critical warming rate was reduced.