OBJECTIVE To investigate the role of mitochondrial permeability transition pore (MPTP) in the cardioprotection by remote preconditioning (RPC). METHODS Remote Precondition (RPC) was induced in anesthetized male Sprague-Dawley rats by three cycles of 5 min of right femoral artery occlusion followed by 5 min of reperfusion. Myocardial ischemia/reperfusion (I/R) injury was achieved by ligation of the left anterior descending coronary artery for 30 min and then reperfusion for 120 min. Infarct size was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining method. The level of lactate dehydragenase (LDH) in plasma and the opening of the mitochondrial permeability transition pore (MPTP) were measured. RESULTS RPC significantly decreased the infarct size and plasma lactate dehydrogenase level induced by I/R, and these effects were attenuated by atractyloside (Atr, 5 mg/kg), a MPTP activator. However, administration of cyclosporin A (CsA, 10 mg/kg), an inhibitor of MPTP, decreased the effect of I/R. In isolated ventricular myocytes loaded with calcein, RPC decreased the MPTP opening, and this effect was attenuated by Atr (20 micromol/L). CONCLUSIONS Inhibition of MPTP opening is involved in the cardioprotection by RPC.