OXIDATIVE STRESS IN RADIATION-INDUCED INTERSTITIAL PNEUMONITIS IN THERAT

The involvement of free radical metabolism in the pathogenesis of inte rstitial pneumonitis was investigated in an animal model. Male Wistar rats were irradiated at the thoracic region by gamma-rays from a Co-60 source. Histopathological examination confirmed that 50% of the rats developed pneumonitis between 2 and 8 weeks following a single dose of 14 Gy. Parallel biochemical studies in the lung of these rats showed that mitochondria and microsomes had higher levels of lipid peroxidati on. In the cytoplasmic fraction of the lung the activities of superoxi de dismutase and catalase were markedly reduced in the pneumonitic rat . In lung mitochondria, however, the levels of these two enzymes were not significantly altered. On the contrary, lipid peroxidation and sup eroxide dismutase, as well as catalase activities in lung tissue in th e non-pneumonitic group of the irradiated rat were comparable with tha t of control animals. The results indicate that free radical-induced o xidative stress following thoracic irradiation may be one of the causa tive factors in the development of interstitial pneumonitis.