Reperfusion duration paradox with late myocardial preconditioning in rabbits

In this study, pharmacological late preconditioning was induced in 53 rabbits with an adenosine A(1) receptor agonist (2-chloro-N(6)-cyclopentyladenosine, CCPA, 100 microg/kg), or a NO-donor (S-nitroso-N-acetyl-penicillamine, SNAP, 2.5 microg/kg/min; 75 min) vs. saline as control. Later, after 24 h, rabbits underwent a 30-min coronary occlusion and subsequent reperfusion. After 3 h of coronary artery reperfusion, infarct size was reduced with CCPA (43+/-4%) and SNAP (27+/-4%) vs. saline (56+/-4%). However, after 72 h of coronary artery reperfusion, infarct sizes were similar in all groups, demonstrating an only transient effect of late preconditioning against myocardial infarction. Combined administration of CCPA and SNAP failed to induce sustained cardioprotection.