Increased Iron Content in Cardiomyocytes of Fpn fl/fl Myh6.Cre+ Mice.
Given the known function of FPN in iron export, we hypothesized that Fpn fl/fl Myh6.Cre+ mice retain more iron within the heart. To test this hypothesis, we compared the cardiac iron content in Fpn fl/fl Myh6.Cre+ and Fpn fl/fl controls at age 3 wk, 6 wk, 3 mo, and 6 mo. At age 3 wk cardiac iron content, as determined by ferritin and total elemental iron concentrations, was comparable in Fpn fl/fl Myh6.Cre+ mice and Fpn fl/fl controls. In both sets of mice cardiac iron content increased gradually over time. However, the rate of this increase was greater in Fpn fl/fl Myh6.Cre+ mice than in Fpn fl/fl littermate controls. At age 6 mo, ferritin and total elemental iron concentrations were 37% and 33% greater, respectively, in cardiac lysates from Fpn fl/fl Myh6.Cre+ mice than in cardiac lysates from Fpn fl/fl controls (Fig. 4 A and B).