Effect of dimethylthiourea on chromium (VI)-induced DNA single-strand breaks in Chinese hamster V-79 cells

The effect of 1,3-dimethyl-2-thiourea (DMTU), a specific hydroxyl radical scavenger on chromate-induced DNA breaks, was studied using Chinese hamster V-79 cells. Incubation of cells with Na₂CrO₄ plus DMTU resulted in a small but significant decrease in cellular levels of the metal-caused DNA single-strand breaks. Electron spin resonance studies showed that DMTU did not affect the formation of chromium (V) complexes either in cells or in the reaction of Na₂CrO₄ with reduced glutathione in vitro, however, DMTU suppressed the generation of hydroxyl radicals in the reaction of hydrogen peroxide and chromium (V) in vitro. Thus, Na₂CrO₄-induced DNA breaks were inhibited by DMTU, possibly due to its ability to scavenge hydroxyl radicals. These and other previous studies indicated that the formation of hydroxyl radicals contribute to the induction of DNA breaks by Na₂CrO₄ in intact cells, but presumably is not the only mechanism involved.