Endotoxin protects against hyperoxic alterations in lung endothelial cell metabolism.

By evaluating the ability of endotoxin to prevent hyperoxic depressions in lung amine uptake, this study assessed whether bacterial endotoxin protects against hyperoxic injury to the pulmonary endothelium. Rats were given 500 or 1,500 micrograms/kg body wt of endotoxin or saline (controls) 30 min before a 24-h or 7-day exposure to air or 100% O2 at 1 ATA. Immediately after exposure, lungs were isolated, ventilated, and perfused via the pulmonary artery and the uptake of two amines, [14C] serotonin and [3H]norepinephrine, was measured. Amine uptake by the lungs of control rats exposed to 100% O2 for 24 h was significantly depressed, whereas amine uptake by the lungs of endotoxin-treated rats exposed to 100% O2 for 24 h was comparable to that in air-exposed controls. Endotoxin also prevented hyperoxic depression of lung amine uptake and prolonged survival in rats exposed to 100% O2 for 7 days. Pretreatment of rats with endotoxin protects against hyperoxic injury to the pulmonary endothelium, which may account for the reduced mortality in endotoxin-treated animals.