Glutathione peroxidase system and lysozyme in rats exposed to ozone or nitrogen dioxide

Exposure of rats to low concentrations of ozone (as low as 0.2 ppm) continuously for 8 days, or intermittently (8 hours/day) for 7 days, significantly increased the activities of the glutathione (GSH) peroxidase system in lung tissue. Linear regression analysis showed the increased enzymic activities to be a function of ozone concentration. Lysozyme activity was significantly increased in lung soluble and plasma, during continuous but not intermittent ozone exposure. The results indicated that lipid peroxidation damage occurred in lungs of rats exposed to relatively high levels of ozone. Rats were exposed to relatively higher levels of nitrogen dioxide for 4 days. The activities of GSH reductase and glucose-6-phosphate dehydrogenase were significantly increased during exposure to 2.3 ppm and 6.2 ppm nitrogen dioxide, respectively. There was no significant increase in the activity of GSH peroxidase in lung soluble, or of lysozyme in the plasma, during exposure to nitrogen dioxide. The results suggest that the mechanism of action of nitrogen dioxide is different from that of ozone.