Objective To investigate the delayed cardioprotective effects of ischemic preconditioning( IPO) and the role of inducible nitric oxide synthase( i NOS) in the late phase of IPO. Methods A total of 160 rats were randomized into 5 groups: I / R group,IPO group,IPO + 1400W( i NOS inhibitor) group,I / R + 1400 W group and sham-operated( sham) group. Animals in each group received 3,24,48 or 72 h of reperfusion after ischemia( n = 8 per each time point). Cardio-infarct size and creatine kinase( CK) activity were...