Effect of oxygen and superoxide anion on mutation rate in Ames test

Effects of oxygen and superoxide anion to mutation rate were examined using the method of Ames. As test samples, 3-methylcholanthrene or 3,4-benzpyrene dissolved in squalene was used. In order to increase the concentration of dissolved oxygen in the medium during preincubation, oxygen was bubbled into the medium. Various combinations of xanthine oxidase, superoxide dismutase and hypoxanthine were used with an intent of changing the concentration of superoxide anion in the medium during the preincubation. An increase in the concentration of dissolved oxygen and superoxide anion resulted in a lower mutation rate, clearly showing the relationships of mutation rate with oxygen and with superoxide anion.