Objective:To investigate the dynamic gene expression of TGF-β1 and MMPsmRNA in pup rats with hyperoxia-induced lung injury.Methods:Thirty-two Wistar rats about two weeks were randomly divided into room-air group and hyperoxia groups(3-day group

7-day group and 14-day group)

with 8 rats in each group.After continuous exposure to high concentration oxygen(O2>95%)

the dynamic expressions of TGF-β1

MMP-2 and MMP-9mRNA in lung for each hyperoxia group were measured by reverse transcript polymerse chain reaction(RT-PCR).The protein content in bronchoalveolar lavage fluid(BALF)

permeability index

lung wet/dry weight ratio and pathological changes of lung tissues were all tested.Results:The level of TGF-β1mRNA in hyperoxia group increased from the 3rd day

and rose gradually until the 14th day.The expressions of MMP-2 and MMP-9 mRNA increased markedly from the 3rd day

rose to the peak at the 7th day

and decreased at the 14th day.The above changes accompanied with lung pathological manifestations

which included acute alveolitis during the earlier period and lung fibrosis during later period.Conclusions:The unbalance between TGF-β1 and MMPs may play an important role in the development of lung fibrosis caused by hyperoxia-induced lung injury.