Abstract: Objective To explore the protective effect of Hypericum perforatum extract (HPE)on myocardial injury in rats with autoimmune myocarditis and its influence on myocardial collagenmetabolism. Methods Six-week-old Lewis rats were enrolled as the research subjects. The experimental autoimmune myocarditis (EAM) rat model was established by subcutaneous injection of porcine cardiac myosin emulsion into the hind foot pad. The EAM model rats were randomly classifiedinto 4 groups: model group, and low-dose, middle-dose and high-dose HPE groups, with 10 ratsin each group. The rats in each group were given intragastric administration of normal saline, 20mg / kg HPE, 50 mg / kg HPE or 100 mg / kg HPE, with twice a day for 28 days. The blank control group was additionally set and was given normal saline according to the same course of treatment. The clinical manifestations of rats were observed, and the heart weight ( HW) and body weight (BW) were measured, and BW/ HW ratio was calculated. The pathological changes of heart were observed under optical microscope after HE staining. Cardiac parameters such as left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), left ventricular fractional shortening (LVFS) and left ventricular ejection fraction (LVEF) were measured by echocardiography. The levels of serum myocardial injury indicators [creatine kinase isoenzyme MB (CK-MB), cardiac troponin T ( cTnT)] and collagen metabolism indicators ( type I collagen, type Ⅲ collagen) were detected, and tumor necrosis factor-alpha ( TNF-α) and transforminggrowth factor-β1 (TGF-β1) protein level was determined by Western blotting. Results The valuesof LVEDD, LVESD, HW/ BW, and the expression levels of CK-MB, cTnT, type I collagen, type Ⅲ collagen, TNF-α protein and TGF-β1 protein in the EAM model rats were increased, the pathological score of myocardial tissues were enhanced, while the values of LVFS and LVEF weredecreased, when compared with those in the blank control group (P < 0. 05). After HPE administration, the values of LVEDD, LVESD, HW/ BW, and the expression levels of CK-MB, cTnT, type I collagen, type Ⅲ collagen, TNF-α protein and TGF-β1 protein were reduced in the lowdose, middle-dose and high-dose HPE groups, and the myocardial tissue pathological score weredeclined, while the values of LVFS and LVEF were risen (P< 0. 05). Conclusion The traditionalChinese medicine Hypericum perforatum extract can improve myocardial injury in EAM model rats,which may be related to its inhibition of myocardial tissue inflammation and reduction of collagen deposition.

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