To compare the distribution of iron in these hearts further, we quantified total elemental iron in cardiomyocyte and noncardiomyocyte fractions isolated from Fpn fl/fl Myh6.Cre+, Hamp−/− hearts and their respective controls at age 6 mo. Results confirmed that, although total iron content was much greater in Hamp−/− hearts, the iron content of the cardiomyocyte fraction was greater in Fpn fl/fl Myh6.Cre+ hearts (Fig. 5E).