Mitigation of pulmonary oxygen toxicity in rats by intratracheal instillation of polyethylene glycol-conjugated antioxidant enzymes.

Hyperoxic lung injury may be mitigated by increasing alveolar epithelial antioxidant activity. We examined whether intratracheal instillation of superoxide dismutase (SOD) and catalase, conjugated to polyethylene glycol (PEG) to permit cellular access, reduces hyperoxic lung injury. Adult rats, pretreated intratracheally with 1,500 U PEG-SOD and 10,000 U PEG-catalase or with inactivated PEG-SOD/catalase, 1% PEG, or saline (treated controls), were exposed to hyperoxia (fraction of inspired oxygen > 0.95) for 48 h and compared with untreated air controls. Alveolar wash protein values in the treated control groups were significantly higher than in the PEG-SOD/catalase and air control groups, which had comparable values. Lung homogenate and alveolar type II cell SOD and catalase activities were higher after PEG-SOD/catalase treatment and lower after the control treatments when compared with untreated air controls. Lung homogenate dipalmitoyl phosphatidylcholine decreased and alveolar wash dipalmitoyl phosphatidylcholine increased after hyperoxia, but these changes were less after PEG-SOD/catalase treatment. Rats pretreated intratracheally with PEG-SOD/catalase survived significantly longer in hyperoxia than saline controls. These data indicate the potential of intratracheal antioxidant treatment to reduce pulmonary oxygen toxicity.