Objective: To observe the effects of paeonol on myocardial pathological changes and expression of transforming growth factor-β1(TGF-β1)and Collagen Ⅲ in rat models with acute myocardial infarction. Method: The left anterior descending coronary branch(LAD) ligation was used to produce in vivo acute myocardial infarction models in SPF male SD rats. Electrocardiogram changes were recorded before ligation

10

20

40

60

120 minutes and 24 hours after ligation

the deviation of ST-segment was measured and analyzed and the successfully modeled rats were randomly divided into the model group

low-

medium-and high-dose paeonol groups

captopril control group

and threaded but not ligated sham group. Low-

medium-and high-dose paeonol groups received ip injection of paeonol at 8.0

12.0

16.0 mg·kg-1 respectively. Sham group and model group received ip injection of the same volume of saline daily. In captopril group

distilled water was used to dilute the crushed powder of captopril tablet and ig applied at 10.0 mg·kg-1.All interventions were done once a day

samples were collected after 28 d

and the pathophysiology changes of myocardial tissues were observed by HE staining

and TGF-β1 and CollagenⅢ protein expression were detected by immunohistochemical assay. Result: HE staining results showed that compared with the sham group

pathophysiological changes were significant in left ventricle of the model group

with cardiac hypertrophy and elongation in edge part of infarct lesions

and part coagulation necrosis in left ventricular wall

nucleus pycnosis of apoptotic cell

anachromasis for cytoplasmic eosin

and part tissues had loose edema. Compared with model group

pathological changes in rats myocardial cells were relieved to certain extents in various treatment groups. Immunohistochemical staining results showed that compared with the sham group

TGF-β1 and CollagenⅢ protein expression levels were significantly higher in the model group(P<0.01). Compared with the model group

TGF-β1 and CollagenⅢ protein expression levels were decreased in all dose paeonol and captopril groups(P<0.05

P<0.01). Conclusion: Paeonol could reduce the myocardial lesion extent in rats with myocardial infarction

improve ventricular remodeling and cardiac function

and its mechanism maybe related to the decrease of the levels of TGF-β1 and CollagenⅢ.