Rat lung antioxidant enzyme induction by ozone.

We exposed rats of different ages (weights approximately 45-300 g) to 0.7 ppm O3 for 1-5 days. At 5 days lungs of O3-exposed rats had higher activity of Cu,Zn superoxide dismutase (SOD), Mn SOD, catalase, and glutathione peroxidase than air-breathing rats; this greater activity was not due to blood-associated enzyme activity. The greater enzyme activity occurred with a higher concentration of the mRNA for each enzyme (Mn SOD not measured) without altered stability of these mRNAs. In adult rats the concentrations of these mRNAs were measured after 1, 3, and 5 days exposure to O3 and were elevated by day 3. The intergroup differences (air vs. O3) among antioxidant enzymes (AOEs) were unequal, and the intergroup differences in concentration of the specific AOE mRNA were greater than the differences in activity of their AOE. We conclude exposure to O3 led to greater expression of AOE genes; the increased expression was mediated pretranslationally probably at the level of transcription.