Deformability of human red blood cells stored for different periods at subzero temperatures

Deformability changes of human red blood cells (RBC) stored for different periods at +4 degrees C, -28 degrees C and -196 degrees C were characterized by a filtration procedure. The filterability index (FI) of RBC stored at -196 degrees C increased (deformability decreased) by about 8%, whereas FI of RBC, liquid stored at +4 degrees C as whole blood, increased by about 25%. In contrast to both the FI of RBC cryopreserved at -28 degrees C for different periods showed an increase of about 40% after 62 days and seemed to be constant for some further months (up to 240 days). A further FI increase was measured after 485 days. Mean cellular hemoglobin concentration changes during storage are excluded to be the cause for deformability loss in this case. An estimation illustrates the osmotic effect of the residual glycerol content after routine deglycerolization procedure and the differences of osmotic and ionic strength effects on RBC deformability in stored blood.