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.