Intestinal iron absorption is impaired in weanling Heph^int/intand Heph^int/ymice. Iron absorption and tissue iron accumulation were quantified in weanling mice, by our standard protocol. Body weights at euthanization (A), blood HB (B), iron absorption (C), and tissue iron accumulation (D-G) in experimental mice are shown. Data are presented as box-and-whisker plots and were analyzed by 2-way ANOVA. No significant 2-way interactions were noted. A sex main effect was noted for Hb levels (P = .0183). Genotype main effects were noted for Hb levels (P < .0001), iron absorption (P = .0022), and liver (P = .0298) and bone (P = .0101) ⁵⁹Fe accumulation. The number of mice in each group is indicated beneath panel A and is the same for data shown in panels B-G. Moreover, enterocyte FOX (H) and serum Cp (I) activities were assessed in weanling mice and also in adults. Data are shown as means ± SD and were analyzed by 3-way ANOVA. Age and genotype main effects were noted for enterocyte FOX activity, as was an age × genotype interaction (all P < .0001). For serum Cp activity, a genotype main effect (P < .0001) and an age × genotype interaction (P < .005) were noted. No significant 3-way interactions were noted for either of these parameters. Also, note that the enterocyte FOX and serum Cp data from adult animals are presented in numerical form in Table 1, but all assays were done simultaneously with adults and weanling mice of both genotypes. The number of mice in each group is shown in parentheses below panels H and I.