Protection against hyperoxia by serum from endotoxin treated rats: absence of superoxide dismutase induction.

Endotoxin greatly reduces lung injury and pleural effusions in adult rats exposed to normobaric hyperoxia (greater than 98% oxygen for 60 hours). This study reports that serum from endotoxin treated donor rats protects serum recipients against hyperoxic lung injury without altering lung superoxide dismutase (SOD) activity. Rats pretreated with endotoxin alone were protected and exhibited an increase in lung SOD activity as previously reported by others. Protection by serum was not due to the transfer of residual endotoxin or SOD. These results show that protection from oxygen toxicity can occur in rats without an increase in lung SOD and suggest that a serum factor may be involved.