PROTECTIVE EFFECT OF HYPOXIA ON OXYGEN-TOXICITY - POSSIBLE MECHANISMS

Abstract

Previous studies demonstrated a protective effect of hypoxia on subsequent death [in rats] breathing O2. Four groups of rats were exposed to air for 120 h plus 99% O2 for 52 h (A + O2); 120 h of hypoxia plus 52 h 99% O2 (H + O2); 172 h of only air (A); and 120 h of only hypoxia (H). Rats were sacrificed and lung lavage protein (gm/100 ml) was 0.57 .+-. 0.18 in A + O2 and 0.26 .+-. 0.12 in H + O2. Hematocrits were increased at sacrifice. Rats with induced hematocrits of 61% did not have a protective effect breathing O2. Mean total phospholipid in lung lavage was: A + O2 O.94; H + O2 1.10; A 1.08; and H 1.76 (.mu.M/ml). Phosphatidyl choline (lecithin) was: A + O2 0.49; H + O2 0.61; A 0.59; and H 1.15 .mu.M/ml. Differences among the groups were significant for total phospholipids and phosphatidyl choline except between air (A) and hypoxia + O2 (H + O2). Palmitic acid was decreased in A + O2 compared to the other groups. O2 breathing results in decreased total phospholipids and phosphatidyl choline in lung lavage. Pretreatment with hypoxia and subsequent O2 breathing results in amounts similar to rats breathing air only.