Abstract:In order to investigate the inhibitory effect of Astragaloside IV(AS-IV) on myocardial injury in rats with myocardial infarction by regulating toll-like receptor 4 (TLR4). Wistar rats were randomly divided into sham operation (Sham), dimethyl sulfoxide (DMSO), model and AS-IV groups with 10 rats in each group. The left coronary artery ligation was used to replicate the myocardial infarction model in the model group, but no ligation was performed in the sham and DMSO groups. In AS-IV group, AS-IV was dissolved in 1% of DMSO and 20 mg·(kg·d)-1 intraperitoneally. The sham group and model group were given the same amount of normal saline, and the DMSO group was given the same amount of saline containing 1%DMSO. All the rats were administered intraperitoneally 1 times a day for 14 consecutive days. The pathological changes of myocardial tissue were analyzed by HE staining, and the apoptosis of cardiomyocytes was detected by the TUNEL method. Reverse transcription quantitative PCR (RT-qPCR) was used to detect the expression of TLR4 mRNA in cardiomyocytes, western blotting and immunohistochemistry were used to detect the expression of TLR4 protein in cardiomyocytes. The results show that AS-IV treatment can significantly reduce the degree of myocardial necrosis, reduce the number of inflammatory cells, reduce the proliferation of scar tissue, significantly reduce the apoptosis of myocardial cells, down-regulate the expression of TLR4 mRNA and protein in myocardial tissue. It is concluded that AS-IV can inhibit myocardial injury by down-regulating the expression of TLR4-like receptor in myocardial tissue of rats with myocardial infarction.