Oxidized heme proteins in an animal model of hemochromatosis

Hemichrome formation resulting from oxidation of heme proteins has been proposed as sensitive indicator of iron-induced oxidative stress. The Heme Protein Spectra Analysis Program was used to quantitate oxidized heme proteins (OHP) in chronic hepatic iron overload in vivo. Rats were fed a diet containing carbonyl iron for 14 months with or without vitamin E supplementation. A 30-fold increase in hepatic iron concentration was observed in rats fed the iron-containing diet. At baseline, total OHP and TBARS were significantly elevated in iron-loaded livers but no increase in hemichrome was seen. During 3 h of spontaneous oxidation, hemichrome formation increased significantly in iron-loaded livers compared to controls. Although supplemental vitamin E was associated with lower levels of OHP and TBARS in iron-loaded livers at baseline, it did not significantly inhibit hemichrome formation during in vitro oxidation. In conclusion, an increase in hemichrome formation in iron-loaded livers was observed only during oxidation in vitro. These results suggest that total OHP is more sensitive than hemichrome formation as an indicator of oxidative stress in this in vivo model of iron overload.