Interactions of cooling rate and protective additive on the survival of washed human erythrocytes frozen to −196 °C

Abstract

Washed human erythrocytes were cooled at different rates to −196 °C in the presence of different concentrations of both penetrating and nonpenetrating cryoprotective additives, and thawed rapidly. The protective effect of albumin when ACD blood is frozen was demonstrated. All compounds tested (glycerol, dimethylsulfoxide, sucrose, bovine serum albumin and polyvinylpyrrolidone) protected the red cells at freezing rates less than that giving optimal survival, and with the exception of polyvinylpyrrolidone, all compounds in high concentration increased freezing damage at faster cooling rates. The net result was to shift the cooling rate giving optimal survival to slower values. The increase in damage at faster rates in high concentrations of the nonpenetrating agents sucrose and bovine serum albumin was unexpected and casts some doubt on the idea that under these conditions nonpenetrating compounds protect the cells by withdrawing water that could otherwise form intracellular ice.