EFFECT OF ISCHEMIA AND REPERFUSION ON THE INTRACELLULAR CONCENTRATIONOF TAURINE AND GLUTAMINE IN THE HEARTS OF PATIENTS UNDERGOING CORONARY-ARTERY SURGERY

Taurine and glutamine are the most abundant intracellular free amino a cids in mammalian hearts where changes in their intracellular concentr ations are likely to influence a number of cellular activities. In thi s study we investigated the effects of ischaemia and reperfusion on th e intracellular concentrations of taurine and glutamine in the hearts of patients undergoing coronary artery bypass surgery using cold cryst alloid or cold blood cardioplegic solutions. Ischaemic arrest (30 min) , using cold crystalloid cardioplegic solution (n = 19), decreased the intracellular concentrations (mu mol/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 taurin e and glutamine was maintained (7.5 +/- 0.5 and 7.4 +/- 0.7 for taurin e and glutamine respectively). Myocardial ischaemic arrest with cold b lood cardioplegic solution (n = 16) did not cause a significant fall i n tissue taurine or glutamine. However, on reperfusion there was a mar ked fall in the intracellular concentrations of taurine (9.4 +/- 0.5 t o 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 la ctate. This work demonstrates that irrespective of the cardioplegic so lution used to arrest the heart, there is a marked fall in tissue taur ine 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, hyp othermia and changes in the transmembrane concentration gradients are the likely factors responsible for the changes in tissue amino acids.