To deplete iron stores (“iron-depleted” condition), mutant mice (Hfe, Tfr2, Hjv and Bmp6) were placed on a low-iron diet and weekly phlebotomies, and strain-matched WT mice (C57BL/6, 129S6, FVB and CD1) were placed on low iron diet for two weeks. An additional control group of C57BL/6 mice (“Ph”) were subjected to low iron diet and phlebotomy. Acute iron challenge consisted of placing the mice on standard chow for 1 day. The values in the graphs represent median and interquartile range. For comparison to chronic liver iron loading (Figure 4, bottom panel), note that the scale for acute iron loading is 5-fold smaller..