title: Hyperoxia inhibits stimulated superoxide release by rat alveolar macrophages.
abstract: Factors responsible for the loss of respiratory burst capacity (stimulated extracellular O2-. release) of alveolar macrophages (AM) exposed to prolonged hyperoxia were assessed. Specific pathogen-free rats were exposed to 1 ATA O2 for 24-72 h, and lungs of survivors lavaged. Release of O2-. by cells after addition of concanavalin A, which stimulated AM but not polymorphonuclear leukocytes (PMN), or digitonin, which stimulated both cell types, was measured using cytochrome c reduction +/- superoxide dismutase. O2-. release by AM declined 47.2% (P less than 0.05) after 24 h of hyperoxia and 100% after 60 h. Percent PMN in the lavage was less than 3% at 0-36 h but increased to 16% at 48 h and to 44% at 72 h. Although addition of PMN to AM in vitro caused inhibition of AM O2-. release, the percent PMN required for inhibition was not reached in vivo until after a significant decline in AM O2-.-releasing capacity had already occurred. Cell-free lavage fluid from either control or hyperoxic rats did not affect AM O2-. release. AM in culture for 24 h in hyperoxia lost 76.7% (P less than 0.005) of O2-.-releasing capacity vs. cells incubated in 20% O2, although dye exclusion was unaffected. The results indicate that the major cause of loss of AM O2-. release by hyperoxia is a direct effect of O2 on the cells.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured; D066298:In Vitro Techniques; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009504:Neutrophils / Q000187:drug effects; D010100:Oxygen / Q000097:blood* / Q000378:metabolism* / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013481:Superoxides / Q000378:metabolism*
chemical_list: D013481:Superoxides; D010100:Oxygen