SummaryEffect of proportion of three branched-chain amino acids (leucine, valine, and isoleucine: BCAA) for nitrogen utilization was studied in vivo by an intragastric administration of 15N-L-leucine to control rats and liver-injured rats treated with carbon tetrachloride (CC1 4-rats). F ollowing the administration of isonitrogenous dose of three amino acid and L-alanine; 11, 8, 6, 18mg/ml), Low-Val (11, 2, 6, 23mg/ml) , and High-Val (11, 32, 6, 0mg/ml)], 15N enrichments in serum albumin , liver, skeletal muscle, and brain proteins and non-protein fractions , and urea nitrogen were compared by using 15N-analyzer. In CCl4-rats , the 15N enrichment in liver protein fraction was significantly lower in the High-Val group than in the Low-Val group. However , the difference of 15N enrichment in serum albumin between Low-Val and High-Val groups in CC1 4-rats was unclear. Th e 15N enrichments in non-protein fractions of the brains in CCl 4-rats were about twofold those in the skeletal muscles and the highest 15N enrichment was recognized in the Low-Val group . In the non-protein fraction of skeletal muscle in CC14-rats , significantly low 15N enrichment was shown in the High-Val group compared with the Low-Val group . The 15 N enrichment in urinary urea was significantly higher in the High -Val group than in the Low-Val group in CC14-rats. In the Standard group of control rats, 15N enrichments in serum albumin and protein fraction of skeletal muscle were higher than in other groups . In non-protein fractions of control rats, the lowest 15N enrichment in liver and the highest 15N enrichment in skeletal muscle were recognized in the Standard group . These results suggest that a large amount of valine supplement among BCAA is less useful for leucine utilization in liver-injured rats than in normal rats.
