【Abstract】 ObjectiveTo explore the expression of endoplasmic reticulum stress (ERS) in rat myocardium with ischemiareperfusion injury and the effect of preconditioning with smalldose tunicamycin on myocardium with ischemiareperfusion injury. MethodsThirty SD rats were randomly divided into 3 groups including shamoperation group (Sham group), ischemiareperfusion injury group (IR group) and tunicamycin + ischemiareperfusion injury ( TM+IR group),ten rats in each group. Simple thoracotomy without coronary artery ligation was performed in the Sham group.Thoracotomy and twohour reperfusion after 30 minutes of the anterior descending coronary artery ligation were performed in the IR group. In the IR+TM group, ligation of the anterior descending coronary artery for 30 minutes was performed after 30 minutes of intraperitoneal injection with tunicamycin (0.6ml/kg), then twohour reperfusion was conducted. The content of cardiac troponin I (cTnI) was detected after thoracotomy and after 2 hours of cardiac reperfusion. The myocardial ultrastructure was observed under transmission electron microscope and the expressions of myocardial glucose regulated protein 78 (GRP78) mRNA and protein were detected after 2 hours of reperfusion. ResultsThe cTnI levels were significantly increased in the IR group and TM + IR group at 2 hours after reperfusion. The damage of myocardial ultrastructure was the most severe in the IR group , and was the second severe in the TM+IR group. GRP78 mRNA and protein expressions increased significantly in the IR group and TM+IR group at 2 hours after reperfusion. ConclusionMyocardial ischemiareperfusion injury (MIRI) may induce ERS. And preconditioning with smalldose tunicamycin may alleviate MIRI.

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