OBJECTIVE The current therapeutic approaches have a limited effect on the dysregulated pulmonary vascular remodeling,which is characteristic of pulmonary arterial hypertension(PAH).In this study we exam-ined whether salvianolic acid A(SAA)extracted from the traditional Chinese medicine′Dan Shen′attenuated vascular remodeling in a PAH rat model,and elucidated the underlying mechanisms.METHODS PAH was induced in rats by injecting a single dose of monocrotaline(MCT 60 mg·kg-1,sc).The rats were orally treated with either SAA(0.3,1,3 mg·kg-1·d-1)or a positive control bosentan(30 mg·kg-1·d-1)for 4 weeks.Echocardiography and hemodynamic measurements were performed on d 28.Then the hearts and lungs were harvested,the organ indices and pulmonary artery wall thickness were calculated,and biochemical and histochemical analysis were conducted.The levels of apoptotic and signaling proteins in the lungs were measured using immunoblotting.RESULTS Treatment with SAA or bosentan effectively ameliorated MCTinduced pulmonary artery remodeling,pulmonary hemodynamic abnormalities and the subsequent increases of right ventricular systolic pressure(RVSP).Furthermore,the treatments significantly attenuated MCT-induced hypertrophic damage of myocardium,parenchymal injury and collagen deposition in the lungs.Moreover,the treatments attenuated MCT-induced apoptosis and fibrosis in the lungs.The treatments partially restored MCT-induced reductions of bone morphogenetic protein typeⅡreceptor(BMPRⅡ)and phosphorylated Smad1/5 in the lungs.CONCLUSION SAA ameliorates the pulmonary arterial remodeling in MCT-induced PAH rats most likely via activating the BMPRⅡ-Smad pathway and inhibiting apoptosis.Thus,SAA may have therapeutic potential for the patients at high risk of PAH. OBJECTIVE The current therapeutic approaches have a limited effect on the dysregulated pulmonary vascular remodeling, which is characteristic of pulmonary arterial hypertension (PAH) .In this study we exam -ined either salvianolic acid A (SAA) extracted from the traditional Chinese medicine’Dan Shen ’Attenuated vascular remodeling in a PAH rat model, and elucidated the underlying mechanisms. METHODS PAH was induced in rats by injecting a single dose of monocrotaline (MCT 60 mg · kg-1, sc). The rats were orally treated with either SAA ( 0.3, 1, 3 mg · kg -1 · d -1) or a positive control bosentan (30 mg · kg -1 · d -1) for 4 weeks. Echocardiography and hemodynamic measurements were performed on d 28.Then the hearts and lungs were harvested, the organ indices and pulmonary artery wall thickness were calculated, and biochemical and histochemical analysis were conducted.The levels of apoptotic and signaling proteins in the lungs were measured using immunoblotting .RESULTS Treatment with SAA or bosentanought am eliorated MCTinduced pulmonary artery remodeling, pulmonary hemodynamic abnormalities and the subsequent increases in right ventricular systolic pressure (RVSP). Stillrther, the treatments significantly attenuated MCT-induced hypertrophic damage of myocardium, parenchymal injury and collagen deposition in the lungs. More over, the treatments attenuated MCT-induced apoptosis and fibrosis in the lungs.Therapeutic partially restored MCT-induced reductions of bone morphogenetic protein type II receptor (BMPRII) and phosphorylated Smad1 / 5 in the lungs.CONCLUSION SAA ameliorates the pulmonary arterial remodeling in MCT-induced PAH rats most likely via activating the BMPRII-Smad pathway and inhibiting apoptosis .hus, SAA may have therapeutic potential for the patients at high risk of PAH.