Use of desferrioxamine as a 'probe' for iron-dependent formation of hydroxyl radicals. Evidence for a direct reaction between desferal and the superoxide radical.

The iron chelator desferal is a powerful inhibitor of lipid peroxidation and of hydroxyl radical formation dependent on the presence of iron salts. Desferal also reacts with superoxide radical with a second-order rate constant approximately equal to 3 X 10(2) M-1 s-1 at pH 10.2 and approximately 9 X 10(2) M-1 s-1 at physiological pH. It is concluded that this slow reaction of desferal with O2- is unlikely to influence the interpretation of experiments in which the chelator is used. The ability of desferal to react with hydroxyl radical (k2 approximately 10(10) M-1 s-1) is a far more likely source of error in the interpretation of results using this chelating agent.