What is the source of free radicals causing hemolysis in stored blood?

The quality of stored blood can be deteriorated by hemolysis caused by free radicals. The purpose of this study was to elucidate whether neutrophile l eukocytes are the source of free radicals in stored blood as in hemodialyze d patients. Resuspensions with low (LL) or high (HL) leukocyte concentratio ns were prepared from samples of twenty healthy volunteers. The samples wer e incubated for 10 days at 4 degreesC and then for one day at 37 degreesC. Markers of hemolysis and free radical metabolism were examined before and a fter incubation in LL and HL samples. In spite of the difference of leukocy tes counts in LL and HL resuspensions (p<0.0001), the pre-incubation values of all laboratory parameters were practically identical. In post-storage s amples, superoxide dismutase and glutathione peroxidase activities did not differ in either group. Reduced glutathione in erythrocytes and extracellul ar antioxidant capacity were insignificantly lower in HL resuspensions, but the increase of malondialdehyde was much more pronounced in the HL samples (p<0.0001). The degree of hemolysis, expressed as the extracellular increa se of potassium (p<0.001), hemoglobin (p<0.05) and lactate dehydrogenase (p <0.05), was higher in the HL samples. Our results support the hypothesis th at leukocytes participate in free radical production in stored blood.