Brain Amino Acids Measured by Intracerebral Dialysis in Portacaval Shunted Rats

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Abstract
Changes in brain amino acid uptake and metabolism have been proposed as a possible etiological factor in hepatic encephalopathy. By use of a brain dialysis technique (a thin tube implanted in the brain of the living animal), the extracellular amino acid concentrations in the striatum of portacaval (PC)‐shunted and shamoperated rats were measured. Leucine, phenylalanine, methionine, and glutamine were increased two‐ to sixfold in the PC‐shunted rats, whilst no changes were seen for GABA, valine, glutamate, or isoleucine, confirming previous reports. Aspartate levels were 350% higher in the PC‐shunted rats, and this rise, as well as that of phenylalanine, was significantly correlated with the lower motor activity observed in the PC‐shunted rats, suggesting a possible importance of these amino acids in the etiology of hepatic encephalopathy. The amino acid concentrations measured in whole blood demonstrated the well‐known pattern of low levels of branched‐chain amino acids and increased concentrations of phenylalanine, glutamine, and histidine.