Possible contribution of oxyhemoglobin to the iron-induced hemolysis simultaneous effect of iron and hemoglobin on lipid peroxidation.

The mechanism of iron toxicity in iron overloaded patients is not well established. A hypothesis was put forward that free radical processes are involved. Our earlier study indicates that iron-induced hemolysis is preceded by peroxidation of the membrane lipids. In the present work the simultaneous effect of iron and hemoglobin on lipid peroxidation was studied. It was found that in hemoglobin-containing liposome suspensions Fe2+ in concentrations above 10(-5) M inhibits the peroxidation, while Fe3+ drastically potentiates it, with concomitant transformation of oxyhemoglobin to methemoglobin. The experiments with scavengers of activated oxygen indicate superoxide anion radical (O-.2), hydroxyl radical (OH.) and singlet oxygen (1O2) participation. The possible mechanism of the phenomenon is discussed. A conclusion is drawn that the toxic effect of Fe3+ may be associated not only with iron--membrane interaction, but also with increased methemoglobin formation and O-.2 release.