Effect of antioxidant therapy on red cell lifespan. Mice that received transplants of Sod2^–/– fetal liver stem cells were divided into 4 groups for measurement of red cell lifespan in the presence or absence of SOD/catalase antioxidant therapy. Group A was pretreated with antioxidant for 4 weeks and continued treatment during measurement of red cell lifespan. Group B was pretreated as Group A, but stopped antioxidant at the time of red cell labeling with biotin. Group C commenced Euk-189 therapy coincident with red cell labeling, whereas group D received sham injections. Error bars = SD.