Muscle and plasma amino-acid patterns in severely depleted surgical patients

Plasma and muscle free amino-acid concentrations were determined in 7 post-operative patients with extensive skeletal muscle protein depletion, and in a group of age- and sex-matched volunteers. All patients had a slightly positive energy balance during the study as verified by indirect calorimetry. In plasma, the concentration of phenylalanine was increased whereas threonine, isoleucine, leucine, serine, glutamine, glycine, citrulline, ornithine, histidine and arginine concentrations were reduced. In muscle, the concentrations of threonine, valine, isoleucine, leucine, phenylalanine, aspartate, glutamate, glycine, alanine and tyrosine were increased, arginine was decreased, whereas glutamine and methionine were normal. The intracellular to extracellular concentration gradients of threonine, valine, isoleucine, leucine, aspartate, serine, glycine, alanine and tyrosine were increased. The plasma concentration of amino-acids correlated inversely with the serum concentration of cortisol. The present results reconfirm some of the previously reported alterations in plasma and muscle amino-acid patterns in traumatised and infected patients. In marked contrast with most previous reports, muscle threonine, aspartate and glutamate concentrations were increased, whereas muscle glutamine concentration was normal. Taking body compositional alterations into account, the findings may in part be explicable on the basis of the high supply of energy and amino-acids in relation to the reduced skeletal muscle protein mass.