The effectiveness of postconditioning and preconditioning on infarct size in hypercholesterolemic and normal anesthetized rabbits

Background: Postconditioning with multiple very short coronary occlusions immediately after prolonged ischemia is a new endogenous mechanism for protection of the ischemic heart. We tested whether postconditioning is effective in limiting infarct size in hypercholesterolemic rabbits. Methods: Male rabbits were fed a cholesterol-enriched diet for 6 weeks. Animals were subjected to 30 min of regional ischemia of the heart and 3 h of reperfusion with the following additional interventions: Control group no additional intervention, ischemic preconditioning (IPC) group to two cycles of 5 min ischemia separated by 10 min reperfusion before the index ischemia, 6110 IPostC group to six cycles of 10 s ischemia separated by 10 s reperfusion and 4130 IPostC group to four cycles of 30 s ischemia separated by 30 s reperfusion immediately after the end of the index ischemia. In a second series of experiments the same interventions were applied to animals fed with a normal diet. Infarct size (I) was determined by triphenyltetrazolium chloride staining. Results: The I/R in hypercholesterolemic rabbits was 55.2 +/- 5.9% in Control, 17.9 +/- 4.2% in IPC (P < 0.01 versus Control), 63.4 +/- 4.8% in 6110 IPostC and 55.6 +/- 8.2% in 4130 IPostC (P = NS between them and the Control group). In the normal diet rabbits, the I/R was 48.2 +/- 4.3% in Control, 15.1 +/- 2.1% in IPC, 20.4 +/- 2.9% in 6110 IPostC (P < 0.01 versus Control) and 45.1 +/- 8.9% in 4130 IPostC (P = NS versus Control). Blood cholesterol levels were increased and atheromatic lesions were present in the first series. Conclusion: Postconditioning is ineffective in limiting the infarct size in rabbits with hypercholesterolemia and atherosclerosis while preconditioning continued to be effective under the same conditions. (c) 2005 Elsevier Ireland Ltd. All rights reserved.