Effect of storage levels of nitric oxide derivatives in blood components

Background: Potential deleterious effects of red blood cell (RBC) transfusions, especially from blood kept at length, have been ascribed to biochemical changes during storage, including those of nitric oxide (NO) metabolism. Study methods and design: In this study, NO metabolites, nitrite and nitrate, were quantified in RBCs and whole blood with time of storage. Whole blood (WB), leukoreduced (LR), and non-leukoreduced (NLR) components were obtained from healthy volunteer donors and stored in polyvinyl chloride bags for 42 days. Nitrite and nitrate were measured using reductive gas-phase chemiluminescence. Results: Nitrite concentrations initially decreased rapidly from about 150nmol/L, but stabilized at about 44nmol/L in room air for up to 42 days. Nitrate concentrations remained stable during storage at about 35µmol/L. Cells from bags maintained in an argon chamber showed decreased nitrite levels compared to those maintained in room air. Inhibition of enzymes implicated in the NO cycle did not alter nitrite levels. Conclusion: As erythrocytes may contribute to the control of blood flow and oxygen delivery through reduction of nitrite to NO under hypoxic conditions, the present findings provide insight into possible effects of blood transfusion. These measurements may explain some adverse effects of RBC transfusion and suggest ways of optimizing the preservation of stored blood.