Objective: To explore the protective effect of matrine on monocrotaline-induced pulmonary arterial hypertension in rats.Methods: Male Sprague-Dawley rats received a single subcutaneous injection of MCT solution (60 mg/kg) to induce pulmonary arterial hypertension( PAH ),the control group were injected by normal saline . Prior to the formation of pulmonary hypertension in rats ,they were given matrine for prevention. 60 male SD rats were randomly divided into 5 groups : pulmonary hypertension group for 4 weeks (MCT4W), matrine low dose group, matrine middle dose group, matrine high dose group , normal control group for 4 weeks (Ctr4W);From the date of injection of matrine ,the matrine groups were treated by different dose matrine with intragastric administration, lasted for 4weeks ,and the normal control group and model group were just treated by saline.When completed experiment , measured right ventricular systolic pressure (RVSP) ,maximal rate of increase and decrease of right ventricular pressure,mean arterial pressure, heart rate.Determine the changes in right ventricular hypertrophy and the ratio of lung . Measured the contents of cTn-I in serum by ELISA.Results:In model group ,the right ventricular systolic pressure, maximal rate of increase and decrease of right ventricular pressure,right ventricular hypertrophy index, lung index,cardiac troponin levels were significantly higher ; in matrine treatment groups ,compared with model group ,there were significant improvement for right ventricular systolic pressure and left ventricular hypertrophy index, cardiac troponin were lower than model group.Conclusion: Matrine showed a protective effect on monocrotaline-induced pulmonary arterial hypertension . Objective:To study ADMA/DDAH2 signal pathway and the expression of eNOS in rats of pulmonary arterial hypertension induced by monocrotaline, in order to clarify the molecular mechanism of the protective effect of matrine on pulmonary arterial hypertension.Methods :Sprague-Dawley rats with subcutaneous injection of monocrotaline (MCT, 60mg/kg) to induce pulmonary arterial hypertension, the models were treated by respectively 25,50 and 100 mg / kg matrine, administered for 4 weeks. ELISA was used to evaluate content of ADMA in blood serum and the expression of PRMT1, DDAH2 ,eNOS in the lung tissues were determined by Western-blot.Results: In model group,the expression of eNOS and DDAH2 were lower with control group, the content of ADMA were higher , had statistical significance;The expression of PRMT1 was higher than control ,but no statistical significance.In matrine treatment groups,the expression of eNOS and DDAH2 were recovered, the content of ADMA were decreased ,but the PRMT1 had no statistical significance.Conclusion: The mechanism of the protective effect of matrine on pulmonary arterial hypertension could regulate ADMA/DDAH2 signal pathway and recover the expression of eNOS .