Expression levels of FPN1 in erythroblasts of mouse BM and in mouse spleen were decreased by hepcidin injection. (A) Expression levels of FPN1 and TfR1 in Ter119-positive erythroblasts or the Ter119-negative cells from BM were compared by Western blot analyses after injection of either hepcidin or PBS for 24 hours. A band from Ponceau S staining of the gel was used as a loading control. (B) Hepcidin injections decreased FPN1 expression in mouse spleen. Expression levels of FPN1, TfR1, L-ferritin, and α-tubulin were measured by Western blot analyses. The experiments were performed in mice maintained on a low-iron diet as described in “Methods.” Experiments in panels A and B were repeated in 3 animals in each group.