Changes in the intracellular free amino acid pool in human saphenous vein tissue culture

Effect of ischaemia and reperfusion on the intracellular concentration of taurine and glutamine in the hearts of patients undergoing coronary artery surgery

Taurine and glutamine are the most abundant intracellular free amino acids in mammalian hearts where changes in their intracellular concentrations are likely to influence a number of cellular activities. In this study we investigated the effects of ischaemia and reperfusion on the intracellular concentrations of taurine and glutamine in the hearts of patients undergoing coronary artery bypass surgery using cold crystalloid or cold blood cardioplegic solutions. Ischaemic arrest (30 min), using cold crystalloid cardioplegic solution (n = 19), decreased the intracellular concentrations (micromol/g wet weight) of taurine (from 9.8 +/- 0.8 to 7.7 +/- 0.7, P < 0.05) and glutamine (8.7 +/- 0.5 to 7.2 +/- 0.6). After 20 min of normothermic reperfusion the fall in taurine and glutamine was maintained (7.5 +/- 0.5 and 7.4 +/- 0.7 for taurine and glutamine respectively). Myocardial ischaemic arrest with cold blood cardioplegic solution (n = 16) did not cause a significant fall in tissue taurine or glutamine. However, on reperfusion there was a marked fall in the intracellular concentrations of taurine (9.4 +/- 0.5 to 6.5 +/- 0.7) and glutamine (8.0 +/- 0.7 to 5.8 +/- 0.4). The fall in amino acids was associated with a fall in ATP and a rise in tissue lactate. This work demonstrates that irrespective of the cardioplegic solution used to arrest the heart, there is a marked fall in tissue taurine and glutamine which may influence the extent of recovery following surgery. The fall in taurine is largely due to efflux whereas changes in glutamine are due to both transport and metabolism. Ischaemia, hypothermia and changes in the transmembrane concentration gradients are the likely factors responsible for the changes in tissue amino acids.