Severe acute oxidant exposure: Morphological damage and aerobic metabolism in the lung

Groups of male rats were exposed to acute doses of oxygen, ozone, or paraquat which produced equivalent mortality (25-30%) over a 28 day post-exposure period. Quantitative evaluation of morphological changes indicated the primary response to be edema and inflammation with only slight fibrosis being apparent by the end of the observation period. Aerobic pulmonary metabolism was inhibited in lungs from animals exposed to oxygen and ozone as evidenced by decreased oxygen consumption; however, this was transient and O₂ consumption returned to normal within 24 hours after removal from the exposure chamber. Conversely, treatment with paraquat caused an immediate, transient stimulation of O₂ consumption. Glucose metabolism was unaltered by the gas exposures and, as previously reported, was initially stimulated by paraquat treatment. In vitro, only paraquat altered both O₂ consumption and glucose metabolism when added to lung slice preparations; ozone had no effect. Oxygen did not alter O₂ consumption but caused a slight biphasic response in glucose metabolism. Aerobic metabolism is relatively unchanged by these doses of oxygen and ozone which result in the death of 25-30% of all treated animals. Even though paraquat produces similar morphologic changes, it may represent a more severe metabolic insult than 'equivalent' doses of oxygen or ozone. Also, if interstitial pulmonary fibrosis is a desired result of experimental exposure, rats may not be a suitable model for oxidant induced lung injury.