ASPARTATE & GLUTAMATE

• Aspartate & glutamate have been shown to improve cardiac recovery after hypoxia or ischaemia under normothermic conditions

• Amino acid supplementation acts mainly by replenishing lost Kreb cycle intermediates & facilitating both anaerobic & aerobic metabolism

• Cardioplegia formulations may be unable to adequately protect damaged hearts suffering pre operative ischaemia or reperfusion injury

• Inadequacy of protection may be due to inability to maintain adequate levels of high energy phosphates in an already energy depleted myocardium or failure to sustain adequate levels glycolysis during the period of ischaemia

• Limitation of energy production by anaerobiosis during hypothermic ischaemia may be related to depletion of key precursors to the Kreb cycle including Glutamate & Aspartate

• Both glutamate & aspartate are lost during ischaemia and are actively incorporated into the myocardium when exogenously supplied

• Both glutamate & aspartate enter the Kreb cycle to yield much needed ATP

• In addition, both glutamate & aspartate may augment production of AMP which may play a role in protecting the heart from ischaemic & reperfusion injury

• Both glutamate & aspartate may play a role in reduction of oxygen free radicals

• Addition of glutamate & aspartate to cardioplegic solution has been shown to increase post ischaemic myocardial performance & oxygen utilisation; the improvement observed being greater in energy depleted hearts

• Both glutamate & aspartate together act synergistically, providing greater protection than either component alone