Plasma amino acids imbalance in patients with liver disease.

The venous plasma amino acid patterns have been determined in 12 normal individuals and in 71 shunted and nonshunted cirrhotics in various grades of hepatic encephalopathy. The free amino acids have been determined by an amino autoanalyzer; the total and free tryptophan have been measured by a spectrophotofluorimetric method. In 14 instances, arterial plasma amino acid patterns have been measured simultaneously. High levels of aromatic and sulfurated amino acids and low levels of branched-chain amino acids have been constantly found in all cirrhotics. Methionine, phenylalanine, valine, leucine, tyrosine, and free tryptophan showed a statistical difference between controls and all other groups. These altered patterns did not correlate either with the grade or the evolution of the coma or with the presence of the surgical anastomosis. No statistical differences were found between arterial and venous values. The only amino acid which statistically correlated with the grade and evolution of the hepatic encephalopathy was free tryptophan. The molar ratios between the amino acids sharing the same transport system across the blood-brain-barrier have been considered. A very good correlation with the grade of the mental disorder was found with the ratios free tryptophan/phenylalanine-tyrosine-methionine-valine-leucine-isoleucine and free tryptophan/branched-chain amino acids.