This study was focused on investigating the involvement of polyamine metabolism in the myocardial ischemia-reperfusion injury (MIRI)in an in vivo rat model. A branch of the descending left coronary artery was occluded for 30 min followed by 2 h, 6 h, 12 h, and 24 hreperfusion. Then the expression of spermidine/spermine N1-acetyltransferase (SSAT) and ornithine decarboxylase (ODC) and theconcentrations of polyamines were assessed. It was found that the expression of SSAT and ODC were upregulated after reperfusion and theconcentrations of spermidine and spermine were significantly decreased, while putrescine concentration was significantly increased. Theresults suggest that MIRI may cause disturbance of polyamine metabolism, and it may play a critical role in MIRI