Spontaneous iron overload in a-thalassemic mice

Because clinical disorders of spontaneous iron overload have no experimental counterpart, we studied iron distribution (atomic absorption analysis) and intestinal absorption (⁵⁹Fe) in mice with hereditary a-thalassemia. Mice heterozygous for a radiation-induced a-Hb gene deletion exhibit a mild hemolytic anemia, like the human condition, with microcytosis, reticulocytosis, splenomegaly, and chemical evidence of defective a-chain synthesis. Quantitative iron determination showed that total iron content in spleen, liver, and kidney, but not heart or lung, of adult a-thalassemic mice was greater (P < .05) than that in unaffected littermates. Iron concentration was also increased in liver (P < .001), spleen (P = .025), kidney (P = .058), and heart (P = .010); in general, the greater the iron concentration in liver, the greater that in spleen (r = .39, P = .009), kidney (r = .79, P < .001), and heart (r = .46, P < .001). In mice examined 8 months postoperatively splenectomy, as compared to sham operation, significantly raised iron content in extrasplenic tissues, but did not affect total body iron. At 10-11 weeks of age, but no longer at 12-14 weeks, thalassemic mice showed higher rates of iron absorption than age-matched controls. Thus, a-thalassemic mice display an early occurring iron absorption defect, leading to a modest, sustained, nonprogressive iron overload, and thereby represent a valuable model for exploring disorders of iron homeostasis.