Abstract: Abstract:Objective  To explore the effects of diammonium glycyrrhizinate on bleomycin induced pulmonary fibrosis (PF) and to further clarify the underlying fibrotic mechanisms.Methods 36 Wistar rats were randomly divided into normal control group,BLM-induced pulmonary fibrosis group(model group) andglycyrrhizinate group.The pulmonary fibrosis models of rats were established by injecting   BLM via trachea (5 mg/kg once).From the 2nd day after injection,the rats in glycyrrhizinate group were intraperitoneally injected with glycyrrhizinate(75  mg/kg/d),while the rats in other two groups with normal saline injection instead.On the 28th day,all rats were sacrificed,the blood samples were obstained to measure inducible nitric oxide synthase (iNOS) and nitric oxide (NO) levels.Their left lung lobe tissues were removed and used for pathological section examination.Results  The pulmonary tissue of the rats in  normal control  group was normal，and the pulmonary fibrosis of the rats in glycyrrhizinate group was significantiy lighter,and the pulmonary fibrosis of the rats in model group was severe.Compared with normal control group，the serum iNOS and NO levels of rats in model group were significantly increased（P<0.01）,but the serum iNOS and NO levels of rats in glycyrrhizinate group had no changes（P>0.05）；the serum iNOS and NO levels of the rats in glycyrrhizinate group were lower than　those in model group（P<0.05 or P<0.01）.Conclusion  Diammonium glycyrrhizinate can significantly reduce the serum levels ofiNOS and NO in BLM-induced pulmonary fibrosis rats and  alleviate pulmonary fibrosis.  

Key words:  , pulmonary fibrosis, bieomycin, diammonium glycyrrhizinate, inducible nitric oxide synthase, nitric oxide