Hyperoxic inhibition of newborn rat lung development: protection by deferoxamine

Prolonged exposure to hyperoxia markedly inhibits normal lung development (alveolarization and respiratory surface area expansion) in immature animals. Since (a) hyperoxia results in excess hydroxyl radical (OH.) formation, (b) (OH.) is implicated in O2-induced lipid peroxidation and DNA alterations, and (c) both OH. formation and its interaction with DNA are Fe++ dependent; chelation of Fe++ should act to protect against pulmonary O2 toxicity and hyperoxic inhibition of lung development. We therefore treated litters of newborn rats with the iron chelator Deferoxamine mesylate (DES) (150 mg/kg/day) during a 10-day exposure to greater than 95% O2. Morphometric analysis demonstrated that compared to the mean airspace size in air control rat pups (Lm = 44.5 microns), hyperoxic exposure resulted in a 34% larger mean air space diameter in O2-saline rat lungs (59.5 microns) versus only an 11% enlargement in O2-DES lungs (51.1 microns*). Lung internal surface area (cm2) per 100-g body weight were air control = 4480, O2-saline = 3570 (decreases 20.3%), and O2-DES = 4125* (decreases 7.9%) (*p less than 0.05 versus O2-saline group). DES-treated animals also had significantly decreased lung conjugated diene levels during hyperoxic exposure and increased lung elastin content (reflective of preserved lung alveolar formation) compared to O2-saline rats. These results indicate that DES treatment substantially ameliorated the inhibitory effects of neonatal hyperoxic exposure on normal lung development.