Background: In a previous study glutamate infusion after coronary artery bypass grafting was associated with beneficial effects on myocardial metabolism and myocardial performance. It has been claimed that aspartate is more important than glutamate for the recovery of myocardial metabolism after cardioplegic arrest. Therefore, the metabolic and hemodynamic effects of aspartate were studied after coronary artery bypass grafting.
Methods: Fifty to 240 mL of a 0.1 mol/L aspartic acid solution was infused intravenously during 60 minutes in 10 patients early after coronary artery bypass grafting. Myocardial metabolism was studied using the coronary sinus catheter technique.
Results: Aspartate infusion caused a significant increase in the arterial levels of both aspartate and glutamate. This was associated with a significant increase in myocardial uptake of aspartate and a decrease in myocardial uptake of glutamate. Myocardial exchange of other substrates remained unaffected. There were no changes in hemodynamic state except an increase of heart rate and pulmonary vascular resistance.
Conclusions: Interactions with glutamate metabolism, compatible with competitive inhibition of myocardial glutamate uptake, which may have outweighed potential effects of aspartate, were observed. Recognition of these amino acid interactions is important as they are used together as additives in cardioplegic solutions.