Figure 4. Changes of oxidative damage parameters in the lung. (A) Changes of antioxidant enzyme activities, GSH and GSSG contents, and GSG/GSSG ratio in the lung at 21 and 42 days of the experiment. (B) Changes of mRNA expression levels of antioxidant enzymes in the lung. Data are presented with the mean± standard deviation (n=8). *p < 0.05, compared with the control group; **p < 0.01, compared with the control group.