Iron accumulation in spleen and liver and correction of anemia with iron dextran in mice lacking Fpn1 in their macrophages. Sex-matched 2-month-old Fpn1^flox/flox (3 male, 3 female) and Fpn1^LysM/LysM (3 male, 3 female) mice were injected intraperitoneally with iron dextran at 250 μg/g body weight. The same volume of PBS was delivered by intraperitoneal injection in the control group (Fpn1^flox/flox, 4 male, 4 female; Fpn1^LysM/LysM, 4 male, 4 female). One week after injection, mice were killed and tissues and blood were harvested for analysis. (A) Spleen and liver nonheme iron concentrations in Fpn1^flox/flox and Fpn1^LysM/LysM mice treated with iron dextran. Fpn1^LysM/LysM mice accumulated more iron than Fpn1^flox/flox controls in both tissues. (B) Iron dextran treatment led to iron accumulation in the spleen and liver as indicated by Perls' Prussian blue staining. Fpn1^LysM/LysM mice accumulated more iron, and this effect was particularly prominent in the spleen. Scale bar represents 100 μm. (C) BMDMs from Fpn1^flox/flox and Fpn1^LysM/LysM mice were loaded with iron by incubation with FAC (100μM) overnight. After removing the medium, cells were washed and then incubated in fresh medium for 0, 6, or 12 hours. Ferritin levels, an indicator of cellular iron stores, were measured by Western blot analysis, and ferritin/actin ratios were also quantitated by densitometry for 3 independent experiments. (D) Western blot analysis of Fpn1 expression in BMDMs from Fpn1^flox/flox mice incubated with FAC. Data are mean ± SEM. *P < .05. †P < .001.