Trauma metabolism and the heart: studies of heart and leg amino acid flux after cardiac surgery.

Flux of plasma amino acids was measured across the heart and the leg (reflecting mainly skeletal muscle) in 18 patients 1 hour after completion of aorto-coronary bypass surgery. There was a net loss of amino acids from the leg (-324.9 +/- 39 nmol/min/100 ml tissue) while amino acid flux across the heart was not statistically different from zero. There were however positive intertissue correlations between leg and myocardial flux of tyrosine and most other amino acids, suggesting that protein metabolism of both tissues were affected in the same catabolic direction by the trauma response. Alanine and glutamine accounted for 50% of the amino acid release from the leg, which is in accordance with observations in association with other types of trauma. Alanine and glutamine also dominated amino acid release from the heart. Glutamate and aspartate were taken up by both tissues. The principal difference between the tissues was a myocardial uptake of leucine and isoleucine, in contrast to a leg release.