Effect of branched-chain amino acids on the composition and cytolytic activity of liver-associated lymphocytes in rats

Background: Although branched-chain aminoacids (BCAA) are reported to be effective in prolongation of the mean survival time of patients with liver cirrhosis, it is not clear whether BCAA could influence the immune function in those patients. Methods: Branched-chain amino acids were given as a supplement to carbon tetrachloride-induced cirrhotic rats, and an aminogram of the liver and kinetics of liver-associated lymphocytes (LAL) were then analysed. Results: Liver cirrhosis was established at the 12th week, and glutathione S-transferase placental form (GST-P)-positive lesions, which are known to be pre-neoplastic lesions, occupied 1.72+/-0.84% of the liver at the 16th week in the controls. At this time the LAL showed an increase in the number of CD5-, CD8- and CD18-positive cells and augmentation of lectin-dependent cellular cytotoxicity (LDCC) activity. Furthermore, supplementation of BCAA increased the number of LAL, especially CD8-positive-cells and natural killer cells, and augmented LDCC activity of LAL at the 16th week. The number of LAL was positively correlated with the valine concentration in the plasma and liver, and the area of GST-P-positive lesions tended to be decreased in the BCAA group. Conclusion: These findings suggest that BCAA administration has stimulatory effects on the local immune systems of the liver, which may have a potential to inhibit hepatocarcinogenesis. Moreover, among all amino acids valine might be an important amino acid for enhancing the immune function of LAL. (C) 2000 Blackwell Science Asia Pty Ltd.