ObjectiveTo investigate the therapeutic effects of different doses of tanshinone ⅡA microemulsion on radioactive lung injury. MethodsSeventy-two Wistar rats were randomly divided into a healthy control group,a model group,a liposome microemulsion treatment group,a tanshinone ⅡA microemulsion high-dose group,a tanshinone ⅡA microemulsion middle-dose group,and a tanshinone ⅡA microemulsion low-dose group.Radiation-induced lung injury model was established by irradiation of radiotherapy instrument.In addition to the control group,other groups received 6MV X radiation with one dosage of 22Gy.Four rats in each group were sacrificed on 7th,14th,and 28th day,respectively.Lung tissues were sampled to analyze the pathological changes by HE staining and the Smad7 mRNA expression by RT-PCR.The level of glutathione(GSH)in peripheral blood was determined by ultraviolet spectrophotometric method. ResultsIn the model group and four treatment groups,lung tissue biopsy showed the pathological changes gradually from pulmonary alveolitis to fibrosis.The level of Smad7 mRNA in lung tissue and GSH in peripheral blood were higher in the high-dose group,the middle-dose group and the low-dose group than those in the model group at all time points(P<0.05),and were highest in the high-dose group.There was no significant differences in the level of Smad7 mRNA in lung tissue and GSH in peripheral blood between the liposome microemulsion treatment group and the middle-dose group. ConclusionTanshinone ⅡA microemulsion has treatment effect on lung injury in a dose dependent manner.