Combined effect of desferrithiocin and L1 on iron/hydrogen peroxide–mediated DNA single-strand breaks. Iron-loaded liver cells were simultaneously exposed to 1 mmol/L L1 and 0.67 mmol/L desferrithiocin for 1 hour, followed by incubation with 100 μmol/L hydrogen peroxide for 30 minutes in the absence of either chelator. Illustrated is a representative experiment performed in duplicate and the values obtained were averaged. Shown are DNA single-strand breaks in control cells exposed to media alone, iron-loaded cells exposed to hydrogen peroxide, iron-loaded cells exposed to desferrithiocin followed by hydrogen peroxide, iron-loaded cells exposed to L1 followed by hydrogen peroxide, and iron-loaded cells exposed to both desferrithiocin and L1 followed by hydrogen peroxide.