Mechanisms of myocardial protection by amino acids: facts and hypotheses.

1. Positive inotropic effect of taurine and improvement of cardiac performance of failing heart are mediated through the modulation of Ca2+ movement through the sarcolemma. 2. Cardioprotection with glutamate and aspartate is related to enhanced anaerobic energy formation in mitochondria coupled with succinate formation and, probably, with the relieving of glycolytic flux. During reperfusion, both amino acids replenish the malate-aspartate shuttle reactants, thereby facilitating glucose oxidation. 3. Increased intracellular concentrations of branched chain amino acids (leucine, valine and isoleusine) stimulate formation of acetyl-coenzyme (CoA) and succinyl-CoA and, thus, recovery of oxidative metabolism. 4. Methionine and cysteine enhance force of contraction by N-methylation of membrane phospholipids of the sarcolemma and sarcoplasmic reticulum. Methionine and, to a lesser extent, cysteine may reduce myocardial damage by oxygen radical species. 5. Histidine exerts antioxidant properties as a scavenger of singlet oxygen and OH radicals. High concentrations of histidine provide intracellular buffering to stimulate anaerobic energy formation.