Objective:To observe the effects of hyperoxiaon the changes of pulmonary histology and surfactant protein gene expression.Methods:SD newborns which less than 6 h old were randomly divided into 2 groups:normal air control group and hyperoxia group.The lungs of rats were removed at the time points 1

4

7

14 d

histopathological changes of the lung tissues were examined by HE staining and the lung factor were calculated(lung weight/body weight ×100%);the expression of all surfactant protein genes were detected by semi-quantitative reverse transcription-polymerase chain reaction(RT-PCR).Results:To compare with corresponding air control group

in hyperoxia group

the body weight is significantly deceased after 14 days of hyperoxia exposure(P<0.01)

and the lung factor increased significantly from day 7(P<0.05)

and kept increasing at 14 d(P<0.05);the levels of SP-A and SP-D mRNAs increased significantlyfromday1(P<0.05)

remained higher at 4 d and 7 d(P<0.05)

and began tosignificantlydecreased at 14 d(P<0.05);the levels of SP-B and SP-C mRNAs increased from day 1(P<0.05)

remained higher at 4 d(P<0.05)

but there were no significant differences at 7 d(P>0.05)

and began to significantly decreased at 14 d(P<0.05).Conclusion:Prolonged hyperoxia can inhibit the development of alveolar and the expression of surfactant protein genes indicating that alterations in gene expression

contribute to tissue injury.