Effect of low levels of ozone on rat lungs. I. Biochemical responses during recovery and reexposure

Studies were made of the effect of 0.8 ppm ozone on selected metabolic activities of rat lungs during initial exposure, recovery, and subsquent reexposure. At the end of a 3 day exposure to 0.8 ppm ozone, the activities of glutathione (GSH) peroxidase, GSH reductase, and glucose-6-phosphate (G-6-P) dehydrogenase were elevated 25, 18, and 46% above controls, respectively. The level of nonprotein sulfhydryl (NPSH) was increased by 24%, general protein synthesis rose by 85%, and the rate of mitochondrial succinate oxidation was 48% above respective control values. During recovery in filtered room air, all the biochemical augmentations began to return toward normal within 2 days and reached control values 6-9 days after the end of initial exposure. Reexposures to 0.8 ppm ozone for 3 days after 6, 13, or 27 days of recovery caused elevations in all the biochemical parameters studied of approximately the same magnitude as the initial exposure. The biochemical findings indicate that, under these experimental conditions, the population of cells present after 6 days of recovery has approximately the same degree of susceptibility to ozone damage as the preexposure population.