Objective: To study the effect and mechanism of saponin of Yulangsan（SYLS） on myocardial ischemia reperfusion injury in isolated rat hearts.Method:Fourteen Wistar rats were randomly divided into five groups: normal group

ischemia reperfusion group

verapamil group（5×10-7 mol·L-1）

and SYLS groups（2×10-2

4×10-2 g·L-1）.Langendorff-perfusion isolated rat hearts were prepared.Myocardial ischemia reperfusion injury was induced by 30 minutes global ischemia followed by 30 minutes reperfusion.The effect of SYLS on cardiac hemodynamics was observed by MPA-CFS.The activities of creatine kinase（CK）

creatine kinase isoenzyme MB（CK-MB）

lactate dehydrogenase（LDH）

lactate dehydrogenase isozyme-1（LDH-1） in the effluent from coronary artery were measured to evaluate the injury of myocardial cells and the protective effect of SYLS.Meanwhile

the activity of superoxide dismutase（SOD） and the contents of malondialdehyde（MDA） in myocardial tissues were determined.Result: Compared with the I/R group

high dosages of SYLS could recover cardiac function

and reduce the releases of CK

CK-MB

LDH and LDH-1 from I/R rat hearts.It could increase the activity of SOD

and decrease the MDA product（P<0.05 or P<0.01）.Conclusion:SYLS may offer myocardial protective effects against ischemia reperfusion injury

which may be related to its effects of scavenging oxygen free radical

reducing lipid peroxidation.