Objective: To investigate the expression of proproteinconvertase subtilisin/kexin type 9(PCSK9) in the rats myocardium impaired by ischemia-reperfusion. Methods:The left descending coronary artery(LAD) of rats was occluded for 45 min, followed by reperfusion of 6,12, or 24 h, respectively. The levels of creatine kinase(CK), creatine kinase MB(CK-MB) and lactate dehydrogenase(LDH) in serum were measured by automatic biochemical analyzer. The pathological changes in myocardium of rat were examined by HE staining. The expression of PCSK9 in myocardium was detected by RT-PCR and Western blot. Results:The levels of CK, CK-MB and LDH were significantly increased after 6 h and 12 h of reperfusion, and restored to normal level after 24 h of reperfusion. The reperfusion-induced myocardial damage increased in a time-dependent manner. The expression of PCSK9 mRNA and protein were significantly and time-depentently increased by ischemia-reperfusion injury. Conclusion:PCSK9 may be invovled in the myocardial ischemia-reperfusion injury.