Free plasma and muscle amino acids in uremic children

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Abstract
In this study changes in extracellular and intracellular free amino acids (AA) were evaluated in uremic children. Free amino acids were studied in eight children with severe renal failure (creatinine clearance < 10 ml/min/1.73 m2). The results were compared to those of 10 controls. Plasma and muscle were sampled after an overnight fast. Amino acids were measured by ion exchange chromatography with a system of five lithium buffers. Plasma of patients showed an increase in total AA due to a rise of nonessential AA. Some AA were significantly increased (P < 0.01): proline, hydroxyproline, glycine, citrulline, and ornithine; (P < 0.05): taurine, asparagine, glutamine, and methionine. Valine and tryptophan were markedly decreased (P < 0.01). The tyrosine/phenylalanine ratio was depressed as well as was the valine/glycine ratio. 1-CH3-histidine and 3-CH3-histidine were present in patients. The muscle pools of essential AA and nonessential AA were increased. All changes in AA concentrations were in the direction of an increase, with the exception of tyrosine. 1- and 3-CH3-histidine were present in two cases. Valine/glycine was decreased. Intracellular/extracellular gradients were decreased for asparate and alanine and were increased for serine, glutamate, methionine, ornithine, and arginine. There was a relationship between the rise of muscle essential amino acids and low-protein intake and growth retardation. No relationship was found between caloric intake, blood glucose, and the glycogenic amino acids.