Objective: To observe the antioxidant effects of modified Bufei Tang (MBT) combined with methylprednisolone on bleomycin-induced idiopathic pulmonary fibrosis (IPF) in rats

and investigate the mechanism. Method: Sixty Sprague-Dawley rats were randomly divided into normal group

model group

methylprednisolone group (10 mg·kg-1·d-1)

MBT group (100 mg·kg-1·d-1)

combined treatment group 1

and combined treatment group 2

n=10 in each group. The IPF models were reproduced by intratracheal injection of bleomycin (1 mg for each rat). 24 hours after modeling

the rats were treated with daily intragastric administration or intramuscular injection until one day before sacrificing. The rats in model group were treated with the same volume of normal saline. Lung coefficient was calculated

and lung tissue morphology changes were observed in IPF rats. The hydroxyproline (Hyp)

malondialdehyde (MDA) and superoxide dismutase (SOD) levels in lung homogenates of rats were measured. Hematoxylin-eosin staining was applied for fixed lung tissues. Result: As compared with the normal group

degree of alveolar inflammatory cells infiltration and pulmonary fibrosis was obvious;lung coefficient was increased significantly;Hyp and MDA levels in liver tissues were increased significantly;and SOD activity in liver tissues was decreased significantly in the rats of model group (P<0.05

P<0.01). Various treatment groups could improve the living state of IPF rats;methylprednisolone group

MBT group

and combined treatment group 1 could significantly improve the degree of alveolar inflammatory cells infiltration and pulmonary interstitial fibrosis of IPF rats

significantly reduce lung coefficient (P<0.01

P<0.05)

reduce Hyp and MDA levels in the lung tissues and increase SOD activity in the lung tissues. Conclusion: Combined treatment group 1 has superior effect than single treatment in reducing liver coefficient

Hyp and MDA levels and increasing SOD activity in the lung tissues of IPF rats. The mechanism might be related to decreasing the level of lipid peroxide to achieve antioxidant effects.