Aim:Compound Radix Salviae Miltiorrhizae Tablets,also known as Fufang Danshen Pian (DSP) in China,has been commonly used in traditional Chinese medicine to prevent and treat cardiovascular diseases (CVD).This study investigated the effects and possible mechanism of DSP against isoprenaline-induced acute myocardial infarction (AMI) in rats by measurements or observation of myocardial enzymes,infarction area,pathological tissue,and so on.Methods:72 male SD rats were randomly assigned t0 6 groups:Control,Model,Isosorbide Dinitrate (2.72mg/kg/d,i.g.),DSP (0.315 g/kg/d,i.g.),DSP (0.63 g/kg/d,i.g.),and DSP (1.26 g/kg/d,i.g.).Each group receivedintragastric administration once daily for ten consecutive days.On the 8th,9th,and 10th days,except for control and model groups,others were subcutaneously injected with 5 mg/kg isoprenaline 30 minutes after intragastric administration once daily to establish AMI models,and electrocardiogram (ECG) was recorded on the 10th day.2,3,5-triphenyltetrazolium chloride (TTC) stain was used for measuring myocardial infarction area,and hematoxylin and eosin (H&E) stain was applied for observing pathological changes in myocardial cells.Changes in concentrations of creatine kinase (CK),lactate dehydrogenase (LDH),troponin Ⅰ (cTn-Ⅰ),nitric oxide (NO),endothelial nitric oxide synthase 3 (eNOS/NOS3) and brain natriuretic peptide (BNP) were determined to discuss the protection effects of DSP on AMI.Results:1.On ECG;the ST segment of the model group was significantly elevated compared with that of the control group.The TTC staining of the heart showed that the control group had no myocardial infarction,but the model group had a greater area of myocardial infarct.There was a significant difference (p < 0.01) between the myocardial infarction area of the model group and the control group.The above results indicated that myocardial infarction models can be established by subcutaneous administration of 5 mg/kg isoprenaline to rats for three consecutive days.2.The mortality rate of rats between the model group and the control group had a remarkable difference (p < 0.05).Although there was no statistical significance between other treatment groups and the model group,the mortality rate greatly declined in other treatment groups compared with that in the model group.3.On ECG,the ST segments of rats in the treatment groups were depressed compared with those in the model group.In the isosorbide dinitrate group and DSP high dose group,the ST segments were depressed to the level of PR segment,and the ECG was restored to normal.4.The myocardial infarction area of rats in the treatment groups decreased remarkably compared with that in the model group.In the isosorbide dinitrate group and DSP high dose group,the infraction areas were relatively smaller.The statistical results showed that isosorbide dinitrate group,DSP high,medium,and low dose groups had significant differences (p < 0.01 0r 0.05) from the model group in myocardial infarction area.5.According to the results of serum CK,the model group showed significant difference (p< 0.01) from the control group.Isosorbide dinitrate group and DSP high dose group had significant difference (p <0.05) compared with the model group.However,DSP medium and low dose groups had no statistical significance compared with the model group.6.According to the results of serum LDH,the model group showed significant difference (p < 0.01) from the control group.Isosorbide dinitrate group,DSP high dose and medium dose groups had significant differences (p< 0.01 0r 0.05) compared with the model group.DSP low dose group had no statistical significance compared with the model group.7.According to the results of serum cTn-l,NO,eNOS,and myocardial tissue BNP,the model group showed significant difference (p < 0.01) from the control group.Isosorbide dinitrate,DSP high,medium,and low dose groups had significant differences (p <0.01 or 0.05) compared with the model group.8.The H&E staining of myocardial tissue showed that the myocardial fibers of rats in the control group were in an orderly arrangement.They were evenly dyed and had clear structures.The myocardium had no atrophy,hypertrophy,necrotic foci,inflammatory cell infiltration or any other pathological changes.The myocardial damages were evident in the model group.The myocardial fibers were in a disorderly arrangement.Myocardial interstitial edema was found,and the tissue space was significantly widened.Neutrophil infiltration was also present.Many myocardial fibers were swollen,lysed,or ruptured,and the cross striation was vague or even disappeared.The myocardial cells underwent vacuolar degeneration.Similar to the control group,the myocardial structure was still complete in the isosorbide dinitrate group.The myocardial damages in DSP high,medium,and low dose groups were milder than those in the model group.Local mild swelling was found,mild interstitial edema was present,and the tissue space was slightly widened.A few inflammatory cells were infiltrated,and vacuolar degeneration could be observed sporadically.Conclusion:The elevation of ST segment on ECG,myocardial cells swelling and necrosis were observed in the model group.Serum myocardial enzymes (LDH and CK),cTn-l and BNP levels also raised in the model group.These evidences demonstrated that AMI models were established successfully.DSP could decrease the mortality rate and myocardial infarct size,and moderately reduce the levels of serum myocardial enzymes (LDH and CK),cTn-l and BNP,thus DSP could inhibit myocardial damages and protect myocardial cells.