RESUMO
BACKGROUND: This study was carried out to determine the effect of the kinds and concentration of cryoprotectants and freezing temperature on the survival rate of frozen erythrocytes. METHODS: Erythrocytes mixed with three different concentrations of amylopectin, k-carrageenan, dextran and hydroxyethylstarch as cryoprotectants were frozen at -10, -30, -50 and -196degrees, respectively, and thawed at 35degrees. The survival rate of frozen erythrocytes was determined by hemoglobin concentration of supernatant of thawed erythrocytes. Morphological changes were observed by scanning electron microscopy. RESULTS: Frozen erythrocytes with amylopectin or k-carrageenan showed relatively low survival rate (<40%). In case of erythrocytes with dextran, the survival rate of erythrocytes with 30% dextran showed significantly increased survival rate compared with 20% or 25% dextran (p<0.05). The survival rates of erythrocytes with 30% dextran and freezing temperature of -10degrees, -50degrees and -196degrees showed 80.44%, 73.61% and 88.84%, respectively. Frozen erythrocytes with hydroxyethylstarch showed significantly high survival rate with freezing temperature of -196degrees (hydroxyethylstarch conc. 20%: survival rate 66.26%, 25%: 64.51%, 30%: 86.22%) compared with other freezing temperature. Most of frozen erythrocytes with amylopectin of k-carrageenan were changed to spherocytes by freezing process. The change to echinocytes of erythrocytes with dextran was decreased according to the increasing concentration of dextran. The change to stomatocytes of erythrocytes with hydroxyethylstarch was decreased according to the increasing concentration of dextran. CONCLUSION: It was found that the kinds and concetration of cryoprotectants and freezing temperature affected the survival rate and morphological change of erythrocytes. Dextran or hydroxyethylstarch could increase the survival rate of frozen erythrocytes over 80% by protection of erythrocytes from the physical, chemical stress during freezing process.