Relationship between erythropoiesis rate and hepatic hepcidin expression. (A) Spleen weight–body weight ratio in control, hypoxic, and EPO-treated mice (50 U for 4 days). (B) Spleen weight–body weight ratio and (C) hepatic hepcidin expression in mice treated with increasing amounts of EPO (total dosage over 4 days is shown) alone (CTL) and in combination with LPS or CI-supplemented diet (CI). (A-C) Data are presented as means plus or minus SD with n = 5 to 6 mice per group. Statistical analysis was performed by 1-way ANOVA; *P < .01 and **P < .001 for comparison with control mice. (D-F) Negative correlation between spleen weight–body weight ratio and hepatic hepcidin expression in mice treated with increasing amounts of EPO: (D) alone (EPO); (E) in combination with LPS (EPO + LPS); and (F) in combination with CI-supplemented diet (EPO + CI). Hepatic hepcidin expression was quantified by real-time RT-PCR and normalized to β-actin. The hepcidin/β-actin ratios are shown.