ASPARTATE GLUTAMATE-ENRICHED BLOOD DOES NOT IMPROVE MYOCARDIAL ENERGY-METABOLISM DURING ISCHEMIA-REPERFUSION - A P-31 MAGNETIC-RESONANCE SPECTROSCOPIC STUDY IN ISOLATED PIG HEARTS/

Objective: Our objective was to test the effects of exogenous L-aspart ate and L-glutamate on myocardial energy metabolism during ischemia-re perfusion, Methods: Phosphorus 31-magnetic resonance spectroscopy was used to observe cellular energetics and intracellular pH in isolated p ig hearts perfused with blood (group A, n = 8) or blood enriched with 13 mmol/L each of L-aspartate and L-glutamate (group B, n = 6), The he arts were subjected to 30 minutes of total normothermic ischemia and t hen reperfused for 40 minutes, Two hearts from each group were inotrop ically stimulated by titration with calcium after normokalemic reperfu sion, Left ventricular function was measured with the use of a complia nt balloon and oxygen consumption was calculated, Results: Magnetic re sonance spectroscopy showed no decrease in the rate of energy decline during ischemia for group B versus group A. No significant differences were observed between the two groups in terms of myocardial function, oxygen consumption, or the rate or extent of high-energy phosphate re covery after normokalemic reperfusion or inotropic stimulation, Inotro pic stimulation of postischemic hearts, however, led to dramatic impro vement in myocardial function in both groups (p < 0.05 for all paramet ers) and significant improvement in oxygen consumption (p = 0.01). Con clusions: In a normal, isolated, blood-perfused pig heart subjected to 30 minutes of total normothermic ischemia, (I) enrichment of the perf usate with aspartate/glutamate before and after ischemia affects neith er myocardial energy metabolism during ischemia-reperfusion nor postis chemic recovery of myocardial function or oxygen consumption and (2) i notropic stimulation can recruit significant postischemic function and sufficient aerobic respiration to support it, irrespective of asparta te/glutamate enrichment.