OBJECTIVE： To determine the cardioprotective ef- fect of magnesium lithospermate B （MLB） on myo- cardial ischemia/reperfusion （MI/R） injury and to in- vestigate the antioxidant potential in vivo and in vitro. METHODS： MI/R injury was induced by the occlu- sion of left anterior descending coronary artery for 30 min followed by reperfusion for 3 h in rats. After reperfusion, hearts were harvested to assess infarct size, histopathological damages, the levels of superoxide dismutase （SOD）, catalase （CAT）, glutathione peroxidase （GPx）, reduced glutathione （GSH） and malondialdehyde （MDA）. Blood samples were collected to determine serum levels of creatine kinase-MB （CK-MB）, cardiac troponin （cTnl） and lactate dehydrogenase （LDH）. Furthermore, simulatedischemia/reperfusion （SI/R） injury in vitro was established by oxygen and glucose deprivation （OGD） for 2 h followed by 24-hour recovery period in cardiomyocytes. The activity of LDH in the cultured su- pernatant and the levels of intracellular reactive oxygen species （ROS）, SOD and MDA in cardiomyo- cytes were also measured. Finally, cardiomyocytes apoptosis was determined with flow cytometry. RESULTS： MLB significantly limited infarct size, ameliorated histopathological damages and prevented leakage of CK-MB, cTnl and LDH. Additional- ly, SOD, CAT, GPx and GSH activities were notably increased by MLB, along with the MDA content decreased as compared with the model group in rats. In vitro study, MLB also decreased LDH activity in the cultured supernatant, increased SOD activity in cardiomyocytes, reduced intracellular ROS and MDA levels, and significantly suppressed cardiomyocytes apoptosis. CONCLUSION： MLB possessed remarkably cardioprotective effects on MI/R injury in vivo and in vitro. The protection of MLB may contribute to its antioxidant properties.
