Glutathione pathway enzyme activities and the ozone sensitivity of lung cell populations derived from ozone exposed...

Rats were exposed to 1.5 +/- 0.1 mg ozone/m3 for 4 days and the activities of glucose-6-P dehydrogenase (G6PDH), glutathione reductase (GR) and glutathione peroxidase (GSHPx) were measured in the cytosolic fraction of lungs from exposed and control rats. Enzyme activities were also measured in isolated alveolar macrophages and type II cells. After ozone exposure enzyme activities, expressed per gram of protein, showed the following changes. G6PDH activity was increased (P less than 0.001) in the whole rat lung and showed the same tendency in isolated alveolar macrophages and type II cells. GR activity did not change significantly neither in whole lungs, nor in isolated cell populations. GSHPx activity was increased (P less than 0.001) in whole lung homogenates, and was also markedly increased in both alveolar macrophages (P less than 0.05) and type II cells (P less than 0.01) isolated from ozone-exposed rats. From these results it was concluded that biochemical changes measured in whole lung homogenates might reflect biochemical changes that occur within specific cell types. Furthermore, it was demonstrated, using an in vitro ozone exposure system, that lung cell populations isolated from ozone-exposed rats, in spite of their marked increase in GSHPx activity, did not show a decreased ozone sensitivity compared to cells from unexposed rats, as determined by trypan blue exclusion or phagocytosis. So an increase in GSHPx activity might not be related to an increased cellular resistance to ozone.