The endotoxin-pretreated, oxygen-adapted rat model in hyperbaric hyperoxia

Rats pretreated with 500 micrograms X kg-1 endotoxin are resistant to the pulmonary toxic effects of normobaric hyperoxia (greater than 95% O2). After endotoxin-pretreatment and exposure to 1.0 ATA O2 for 72 h, such rats are found to have elevated total superoxide dismutase, glutathione peroxidase, and catalase activities in homogenates of whole lungs. Despite increases in these protective antioxidant enzymes which persist in 2.0 ATA O2 (4 h) and 4.0 ATA O2 (1.0 h), such rats do not have improved survival in hyperbaric hyperoxia. Likewise, endotoxin-pretreatment immediately prior to 2.0 or 4.0 ATA O2 exposure does not prolong survival compared to controls. It is likely that lung injury during the normobaric oxygen preexposure and the central nervous system toxicity of hyperbaric oxygen interact to limit survival.