Abstract： Objective To observe the effects of Wenxin Granules on isoproterenol(ISO)-induced myocardial fibrosis in rats through β1-AR/TGF-β1/Smad2 pathway.Methods 60 male Sprague Dawley(SD)rats were randomly divided into six groups:control group,ISO group,Wenxin Granules low-dose,middle-dose,and high-dose groups,and amiodarone group,with 10 rats in each group.The drugs were continuously given for 14 days.Starting from day 15,rats in ISO group,and treatment groups were given the hypodermic multi-point injection of ISO for 14 consecutive days to establish the myocardial fibrosis model in rats.The changes of heart weight index in rats were detected.The cardiac morphological changes were observed by hematoxylin-eosin staining(HE),and the changes in cardiac collagen distribution and content were observed by Masson staining.The levels of HYP,GSH-PX,sympathetic nervous system-β1 adrenergic receptor(β1-AR),transforming growth factor β1(TGF-β1)and p-Smad2 in rat myocardial were determined.Results Compared with rats of control group,the heart weight index in rats of ISO group were obviously elevated,the cellular structure was disordered,and collagen deposition and myocardial fibrosis were significant.Myocardial HYP levels were markedly elevated,and the GSH levels were obviously reduced.The myocardial β1-AR,TGF-β1 and p-Smad2 levels of ISO group rats were sig-nificantly increased(P<0.05,P<0.01).While compared to rats of ISO group,the heart weight index of rats in each treatment groups were decreased,the cardiac structural disorder and collagen deposition were alleviated,and myocardial fibrosis was significantly improved,the HYP levels showed a significant decrease and the GSH levels showed a slight increase,and β1-AR,TGF-β1and p-Smad2 levels were decreased(P<0.05,P<0.01).The therapeutic effect of high-dose Wenxin Granules group was more remarkable than that in low-dose Wenxin Granules group(P<0.05),with no obvious difference compared with amiodarone group.Conclusion Wenxin Granules can improve ISO-induced myocardial fibrosis,alleviate myocardial cell damage and collagen fiber accumulation,and its mechanism may be related to β1-AR/TGF-β1/Smad2 pathway.