Glucose use in neonatal rabbit hearts reperfused after global ischemia

In this study, we measured both glycolysis and glucose oxidation during reperfusion of previously ischemic hearts obtained from 7-day and 6-wk-old rabbits. Isolated working hearts perfused with 11 mM [3H/14C]glucose, 0.4 mM palmitate, 0.5 mM lactate, and 100 microU/ml insulin were subjected to either 30 or 40 min of global ischemia followed by a 60-min period of reperfusion. Recovery of mechanical function was 58% in 7-day-old hearts subjected to 40 min of ischemia. In 6-wk-old rabbits, a 45% recovery of function was seen after only 30 min of ischemia. Addition of 1 mM dichloroacetate (DCA) to the perfusate at reperfusion increased glucose oxidation rates during reperfusion in both 7-day and 6-wk-old hearts (from 102 +/- 22 to 262 +/- 27 and from 280 +/- 63 to 523 +/- 97 nmol.min-1.g dry wt-1, respectively). Addition of DCA, however, resulted in a significant improvement in recovery of mechanical function only in 6-wk-old hearts (from 45 to 67% of preischemic function). These results demonstrate that fatty acid-perfused neonatal rabbit hearts are more able to tolerate ischemia than the matured rabbit hearts. However, our data suggest that there may be less potential to improve mechanical recovery in neonatal hearts during the actual reperfusion period by stimulating glucose oxidation.