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, 6/10 IPostC group to six cycles of 10 s ischemia separated by 10 s reperfusion and 4/30 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 6/10 IPostC and 55.6 ± 8.2% in 4/30 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 6/10 IPostC (P < 0.01 versus Control) and 45.1 ± 8.9% in 4/30 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.