Oxygen toxicity in newborn rats: the adverse effects of undernutrition

Undernutrition was found to compromise the tolerance of newborn rat pups to hyperoxia (greater than 95% O2 for 7 days). Survival rate for the normally nourished pups (11 pups/dam) was 56 of 77 (73%) but only 47 of 108 (44%) for the undernourished (18 pups/dam) group (P less than 0.005). Body growth, lung growth, and lung DNA content were significantly reduced by undernutrition. Hyperoxia inhibited these same parameters in both groups of pups. The growth inhibitory effects of O2 and undernutrition were additive, with an especially marked depression of lung DNA content (decreases 65%). Lung maturation was also markedly inhibited by O2 but to a similar extent in both nutrition groups. Despite the disparity in their O2 tolerance, 18/litter and 11/litter pups in O2 responded with equivalent increases in lung antioxidant enzymes. We suggest that the additive depressive effects of neonatal undernutrition and hyperoxia on lung DNA may compromise repair of ongoing O2-induced lung damage and help account for the compromised O2-tolerance we consistently observed even in the presence of significantly elevated antioxidant enzyme defenses.