Effect of ischemic preconditioning on carnitine-linked metabolism in the rabbit heart

Background The current study was undertaken to assess whether brief periods of ischemic preconditioning influence fatty acid metabolism during a longer period of ischemia in the rabbit heart. Methods Four experimental groups of rabbits were studied: group 1, sham-operated rabbits; group 2 (ischemia), 15-minute occlusion of the coronary artery; group 3 (reperfusion), 15-minute occlusion then 15 minutes of reperfusion; and group 4 (preconditioning), two 5-minute occlusions each followed by 10 minutes of reperfusion, then 15 minutes of occlusion and 15 minutes of reperfusion. ATP, creatine phosphate, glucose-6-phosphate, and lactate content as well as free carnitine and short- and long-chain acyl carnitine concentrations in the heart were studied. Results Reperfusion (group 3) and preconditioning (group 4) normalized glucose-6− phosphate levels and reduced accumulation of lactate in the previously ischemic area. Ischemia alone caused a significant accumulation of long-chain acyl carnitine and short-chain acyl carnitine in the ischemic area (from 35.3 ± 5.9 to 53.9 ± 3.5 nmol/g and from 224,7 ± 86.8 to 560.6 ± 34.6 nmol/g respectively; P< 0.05). The levels of long-chain acyl carnitine and short-chain acyl carnitine were not significantly influenced by reperfusion and remained increased in the previously ischemic tissue in group 3. Preconditioning significantly reduced accumulation of both long-chain acyl carnitine and short-chain acyl carnitine in the previously ischemic area. Conclusions These results suggest that brief periods of preconditioning ischemia may cause favorable alterations in carnitine-dependent metabolism in rabbit hearts subjected to a longer period of ischemia followed by reperfusion.