Abstract:OBJECTIVE: To study the deleterious effect of prolonged hyperoxia exposure on preterm rat lungs. METHODS: On the 2nd postnatal day, preterm SD rats were randomly assigned to the air group (I) and hyperoxia group (II, exposed to 85% O2). After 3, 7 and 14 days of exposure, the contents of total protein (TP), hydroxyproline (HYP) and malondialdehyde (MDA), total cell counts and differentiation in bronchoalveolar lavage fluid (BALF), ratio of lung wet weight/dry weight (W/D), and lung collagen content were examined. After 3, 7, 14 and 21 days of exposure, lung histopathology and radial alveolar counts (RAC) were performed. RESULTS: On day 3 of hyperoxia exposure, only the MDA content increased in Group II(P<0.05). On day 7 and 14, TP, HYP, total cell counts, the percentage of neutrophils in BALF and lung W/D also significantly increased ( P < 0.05 or 0.01). The differences of lung collagen contents between the two groups were not significant ( P >0.05). Hyperoxia exposure resulted in subacute alveolitis and inhibition of lung development on day 7, 14 and 21. RAC was similar between the two groups on day 3 (4.9±0.7 vs 5.0 ±0.8), but different on day 7 (5. 9 ± 0.9 vs 7.1 ± 0. 9; P <0.05. On day 14 and 21, RAC decreased more obviously in Group II compared with that in Group I (7.0±0.8vs9.9±0.6, 7.3 ± 0.9vs10.5±0.8; P <0.01). CONCLUSIONS: Prolonged exposure to 85% O2 may result in subacute inflammatory lung injury and inhibition of lung development in preterm rats.
