Cerebral amino acid levels and transport after portocaval shunt in the rat: effects of liver arterialization.

Altered plasmatic and cerebral amino acid patterns have been observed after portocaval shunt in the rat. Similar alterations have been found in plasma and in cerebrospinal fluid of cirrhotic patients and are likely to play an important role in the pathogenesis of hepatic encephalopathy. Impaired liver blood flow could contribute to these biochemical abnormalities. Therefore we wondered whether liver arterialization, by improving liver perfusion, could have any beneficial effects on the altered amino acid levels occurring in the rat after portocaval shunt. Amino acid concentrations were determined in four cerebral regions and in the plasma of shunted rats with or without liver arterialization, 4 weeks after surgery. Blood-brain barrier transport was studied with the Oldendorf's technique. After portocaval shunt, we observed lower plasma levels of the branched chain amino acids valine, isoleucine, leucine, and net higher levels of the aromatic tyrosine and phenylalanine and of glutamine. In the cerebral regions, we observed a slight increase of branched chain amino acids and an enormous increase of tyrosine, phenylalanine, tryptophan, histidine, and glutamine. Arterialization of the liver made no difference to the postportocaval shunt plasma levels of branched chain amino acids, while it almost normalized those of aromatics. In the cerebral regions, we observed a marked improvement in the level of tyrosine, phenylalanine, tryptophan, and histidine. The enhancement of blood-brain barrier transport for the neutral amino acid class, observed after portocaval shunt, was not influenced by liver arterialization. We conclude that, in our model, liver arterialization improves the pathologic amino acid levels following portocaval shunt. This would be in agreement with clinical reports suggesting that hepatic encephalopathy is less frequent after portocaval shunt when associated with arterialization of the liver.