Pulmonary NO2 toxicity in neonate and adult guinea pigs and rats

The pulmonary effects of NO2 were investigated in two animal species. Rats and guinea pigs aged from 5 to 60 days or more were exposed for 3 days either to 2 ppm or to 10 ppm NO2. Lung histology or superoxide dismutase (SOD) determination in alveolar macrophages was assessed in air and NO2-exposed animals. Results demonstrated that the lung histological alterations are different for both NO2-exposed species. Rats were more tolerant than guinea pigs, but rat and guinea pig newborns were less affected than adults. The enzyme response to NO2 exposure was similar in both species and a decrease in SOD activity was noted in animals of all ages. These observations support the conclusion that NO2 exposure leads to increased lung damage during the life span, but on the contrary, exposure to oxygen does not involve SOD induction. This suggests that the defense mechanisms against NO2 are different from those of O2.