Objective      To investigate the Rho kinase inhibitor fasudil (FAS) in neonatal rats with hyperoxia-induced lung fibrosis.       Method      According to the random number tables

twenty-four Sprague-Dawley neonatal rats were randomly divided into 4 groups: air + normal saline (NS) group

air + FAS group

hyperoxia + NS group and hyperoxia + FAS group. After 21 d

the subjects were sacrificed. The changes of lung histomorphology were observed. Hydroxyproline in the lung was detected by sample hydrolysis method. α-smooth muscle actin (α-SMA) protein expression in the lung was determined by immunohistochemistry assay and Western blotting.       Results      Pathological examination showed structural disorder and obvious fibrosis in the lung tissues of hyperoxia + NS group and the signs of improvement in the lung tissues of hyperoxia + FAS group at 21 d. The content of hydroxyproline and α-SMA protein expression in lung tissues were both increased markedly at 21 d in the hyperoxia + NS group and hyperoxia + FAS group compared with the air groups

and were significantly lower at 21 d in the hyperoxia + FAS group than in the hyperoxia + NS group.       Conclusion      Rho kinase inhibitor fasudil has obvious therapeutic effects on hyperoxia-induced lung fibrosis

probably through myofibroblast inhibition.