Kidney iron loading. (A) Iron concentrations in kidney samples from 1-, 2-, and 3-month-old wild-type, Hp-null, Hfe-null, and HfeHp double-null F₂ mice. Symbols indicate same groupings as in Figure 1. Results are expressed as mean ± SEM; n = 10 for each group. There was a tendency for higher kidney iron content in Hp-null and HfeHp-null mice compared with wild-type and Hfe-null mice, respectively, at 1 and 2 months of age but the difference was not statistically significant. There were strongly significant differences between Hp-null and wild-type mice (P ≤ .001) and between HfeHp-null and Hfe-null mice (P ≤ .001) at 3 months of age. (B) Kidney sections from wild-type, Hp-null, Hfe-null, and Hfe and Hp compound mice stained with Perls reaction. Note iron deposits in proximal tubular cells in Hp-null and HfeHp-null mice. Bar = 100 μm.