The effect of vitamin C on oxygen radical-induced sister-chromatid exchanges

We studied the effects of vitamin C (sodium ascorbate) on the genotoxicity of oxygen radicals to tissue culture cells. Chinese hamster ovary cells (CHO cells), when exposed to an enzymatic oxygen radical generating system (xanthine oxidase plus hypoxanthine), develop increased numbers of sister-chromatid exchanges (SCEs). Inclusion of ascorbate in these incubations resulted in significant, but variable effects. In some cases, ascorbate (less than 0.1 mM) was protective and fewer SCEs were produced. In others, significant augmentation of oxygen radical-induced SCEs occurred. These experiments illustrate the complexity of the interactions of ascorbate in biologic systems and the difficulty of predicting a desirable or harmful effect.