General correlation of Steap3 to RBC storage across strains and in vivo RBC life span. (A) Ferrireductase activity in RBCs as measured by using ferrozine as an indicator of Fe²⁺. Data shown represent combined means from 3 independent experiments (n = 2-4 mice per group, per experiment). Statistics were calculated by using 2-way ANOVA with a Bonferroni post hoc analysis. At the highest concentration of RBCs tested (inset graph), ferrozine activity of B6 is significantly lower than all other strains tested (***P < .0001). (B) Western blot of RBC ghosts using an anti-Steap3 antibody. After development, membranes were stripped and re-probed with anti-actin as a control for loading and transfer. (C) RBC life span determination by in vivo biotinylation. These data represent means ± SD from a representative experiment (n = 5 mice per group). These data have been replicated in at least 3 experiments.