Free radical species mediating the toxicity of ozone for cultured rat lung fibroblasts.

We have reported a model system with which to study factors influencing the toxicity of O3 for cultured rat lung cells. This continuing investigation was to determine the relative contributions of free radical species to the toxicity of O3 as measured by 51Cr release and the use of free radical scavengers. Toxicity from modes of O3 exposure favoring stable free radicals (stationary cultures or added O3-exposed medium) was prevented by the H2O2 scavenger, catalase. Toxicity produced by exposing cells to O3 through only a thin film of medium (rotated cultures) was partially prevented by either catalase or superoxide dismutase. Their combination completely prevented toxicity, suggesting that both H2O2 and O2 were major toxic species. Mannitol, an OH scavenger formed from H2O2 and O2, was partially protective with all models while the 1O2 scavengers histidine, tryptophan and xanthine were ineffective.