Objective:To investigate the protective effects and mechanism of oxymatrine（OMT） on experimental acute myocardial infarction（AMI） in rats induced by ligatting left anterior descending branch of coronary artery.Method:The SD rats were allotted into 4 groups according to the body weight as following:sham operation

model group

the OMT 50 mg·kg-1and 25 mg·kg-1 groups

the rats were orally administered for 5 days.The rat AMI model was reproduced by ligation of left anterior descending branch of coronary artery after 1 hour of the last treatment

the ligation of the artery did not be performed in sham operation group.The sample was collected after ligation of left anterior descending branch of coronary artery for 6 hours.The pathological changes of cardiac tissue were checked by HE staining.The indexes of oxidative stress were detected by biochemical assay kits

including the total antioxidant capacity（T-AOC）

activities of superoxide dismutase（SOD）

catalase（CAT）

glutathione peroxidase（GSH-Px）

and malondialdedyde（MDA） content.And the contents of the interleutin-1β（IL-1β）

interleutin-6（IL-6）

and tumor necrosis factor-α（TNF-α） in serum were measured by Elisa kits.Result:The histological examination indicated there was a myocardial lesion in model group including edema of myocardial interstitial and inflammatory cell infiltration

etc

after ligation of left anterior descending branch of coronary artery

OMT 50 mg·kg-1 could ameliorate the histopathological changes.The activities of antioxidant enzymes in serum were significantly decreased such as SOD

CAT

and GSH-Px

as well as MDA contents in serum were increased

and the contents of IL-1β

IL-6

and TNF-α in serum were increased in model group（compared with sham group

there were significant difference

P<0.01 or P<0.05）.50 mg·kg-1 OMT could obviously ameliorate oxidative stress and inflammatory cytokines in serum（compared with model group

P<0.01 or P<0.05）.Conclusion:OMT can protect the cardiac injury in rats induced by ligating left anterior descending branch of coronary artery

the mechanism maybe involve in inhibiting secretion of inflammatory cytokines and ameliorating oxidative stress.