Aim 2: To transfuse healthy volunteers and investigate the effects of storage-related RBC changes on blood flow, tissue oxygenation, and biomarkers of cardiovascular function. The investigators will determine whether RBCs prepared and stored under conditions that alter NO bioavailability in vitro (Aim 1) inhibit NO-mediated vasodilation, reduce tissue perfusion, and decrease tissue O2 delivery in healthy transfusion recipients in vivo. The role of 2,3-DPG depletion as well as exercise-induced O2 demand will also be investigated with these specialized experimental systems.