Objective    To investigate the effect of hyperoxia on p38MAPK expression and apoptosis in the lungs of juvenile rats.     Methods    Thirty-two Wistar rats aged 3 weeks were divided into air exposure group and 1-day

2-day and 3-day hyperoxia exposure groups

with 8 rats in each group. The hyperoxia exposure rats were exposed to 90% O

2

. The resected lungs were histopathologically examined. The apoptosis and p38MAPK expressions in the resected lungs were detected by TUNEL and Western blot respectively.     Results    After 3-day hyperoxia exposure

the pathological changes of acute lung injury occurred

such as edema

hemorrhage and inflammatory cell infiltration. The apoptosis

index in the lungs of 3-day hyperoxia exposure group was significantly higher than that of air exposure group (P0.05)

and TUNEL showed the apoptotic cells were mainly distributed in the alveoli

airway epithelial cells and pulmonary vascular endothelial cells. Western blot results showed that p-p38 MAPK increased at the 1

st

day after hyperoxia

peaked at the 2

nd

day and decreased at the 3

rd

day.     Conclusion     In the course of hyperoxia-induced lung injury

high oxygen concentration can induce cell apoptosis and activiate the p38 MAPK signal pathway. The activiated p38MAPK signaling pathway may play a role in the regulation of apoptosis induced by hyperoxia.