Objective: To determine the angiogenesis effect of radix astragali extract on myocardium of rats with myocardial infarction (MI) and analyze its possible mechanism. Method: Left coronary arteries of Sprague-Dawley rats were ligated to make MI models. The rats were randomly divided into MI model group

3 different dose groups of Astragali Radix extract (10

20

40 mg·kg-1·d-1)

and the sham operation group. Each group consisted of 8 rats. All the treatment groups were orally fed with the drug extract of above corresponding dose

and the model group and sham operation group were fed with normal saline 20 mL·kg-1·d-1. 4 weeks later

hematoxylin and eosin staining

Masson staining

and electron microscope were taken to analyze the left ventricular myocardial tissue and vascular pathological changes in rats with MI

and immumohistochemical staining was taken to analyze the expression changes in vascular endothelial growth factors (VEGF) and CD34 proteins. Result: Compared with the sham operation group

myocardial tissue was disordered in the model group

accompanied by severe myocardial necrosis

significantly reduced quantity of complete microvessel (P<0.05)

significantly increased collagen content (P<0.01)

and obvious endothelial cell loss (P<0.05). Compared with the model group

the structures of myocardial tissue in all the treatment groups were relative regular

with significantly increased collagen content (P<0.01)

significantly increased number of new microvessels (P<0.05)

as well as relatively complete endothelial cell morphology and increased number of endothelial cells (P<0.05). In addition

VEGF and CD34 protein expression in the cytoplasm of myocardial tissue was increased significantly (P<0.01). Conclusion: Astragali Radix extract can obviously improve the disorganized myocardial tissue of rats after myocardial infarction

and promote angiogenesis in the impaired myocardial tissue.