Overview of arginine (ARG) and NO metabolism in the supernatants of RBCs stored for 5 and 42 days and in the plasma of autologous recipients pre- and posttransfusion of the same units. (A) Arginine and its downstream metabolites. (B) Outline of arginine metabolism by NO synthase (NOS) and arginase. (C) Determination of arginine fate. **P < .01 (2-tailed paired Student t test). CTR, citrulline; ORN, ornithine.