Polyethylene glycol-attached antioxidant enzymes decrease pulmonary oxygen toxicity in rats

When exposed continuously to hyperoxia (100% O2, 760 Torr barometric pressure), rats pretreated with polyethylene glycol (PEG)-attached superoxide dismutase and catalase (PEG-SOD + PEG-CAT) lived longer (79.1 + 7.6 h) than rats pretreated with saline (60.7 +/- 2.1 h) or PEG-inactivated-SOD + PEG-inactivated-CAT (62.3 +/- 1.6 h). Rats pretreated with PEG-SOD + PEG-CAT also had less hyperoxia-induced acute oxidative edematous lung injury, as assessed by increases in lung oxidized glutathione (GSSG) contents, pleural effusions, and lung lavage albumin concentrations than saline-pretreated rats. Rats pretreated with the long-lived conjugates PEG-inactivated-SOD + PEG-inactivated-CAT or PEG-albumin also had decreased acute oxidative edematous lung injury compared with rats pretreated with PEG, SOD + CAT + PEG, SOD + CAT, or saline. In vitro studies suggested that PEG itself may have contributed to protection by scavenging hydroxyl radical (.OH) but not superoxide (O2-.) or H2O2. Compared with more effective endogenous (via preexposure to hypoxia) or exogenous (via liposomes) means for increasing lung antioxidant enzymes, PEG enzymes are less protective against lung injury from continuous hyperoxia.