Interestingly, the degree of cardiac iron loading, as assessed by ferritin and elemental iron content, was much greater in Hamp−/− mice (∼450% increase relative to Hamp+/+ controls) than in Fpn fl/fl Myh6.Cre+ mice (∼30% increase relative to Fpn fl/fl controls). However, Perls iron staining showed that, although iron accumulated primarily within cardiomyocytes in Fpn fl/fl Myh6.Cre+ hearts (Fig. 4D), ferric iron deposits in Hamp−/− hearts were localized primarily in noncardiomyocytic cells (Fig. 5B). Electron micrograph images of Hamp−/− hearts showed the presence of iron deposits in the endothelium and intracapillary leukocytes (Fig. 5C).