The ability of SS mouse BM to compensate for anemia was impaired. (A) Plasma EPO levels of various mice as indicated (N = 6). (B) Fold change of BFU-E colony numbers in 5 ×10⁴ BM cells (N = 6). (C) Fold change of CFU-E colony numbers in 5 × 10⁴ BM cells (N = 6). (D) Fold change of BM erythroblast numbers in 2 femurs + 2 tibias (N = 6). Data in panels B, C, and D were normalized by dividing them by the average of the control group. (E) Numbers of BFU-E colonies in 200 sorted BFU-E (N = 6). (F) Numbers of CFU-E colonies in 200 sorted CFU-E in the presence of EPO at the indicated concentrations (N = 6). ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. N.S., no statistical difference.