ARGININE-ENRICHED SOLUTION INDUCES A MARKED INCREASE IN MUSCLE GLUTAMINE CONCENTRATION AND ENHANCES MUSCLE PROTEIN-SYNTHESIS IN TUMOR-BEARING RATS

Using a transplantable Yoshida sarcoma in a rat model of total parente ral nutrition (TPN), we measured the effectiveness of an arginine-enri ched amino acid solution (AI-82) on muscle glutamine concentration and muscle protein synthesis compared with that of a conventional amino a cid solution (Proteamin12). After tumor-bearing rats had been given on e of two isocaloric TPN regimens for 6 days, [N-15]glycine (99 atom %) containing TPN solution was infused into animals at a constant rate o f 8 mg of [N-15]glycine per hour for is hours, after which the liver, skeletal muscle (gastrocnemius muscle), and tumor protein synthesis ra tes were measured. A significantly increased whole muscle protein synt hesis rate was observed in the AI-82 group; there was no difference in the whole liver and tumor protein synthesis rates between the two gro ups. When each TPN solution was administered for 1 week, muscle concen trations of arginine, ornithine, glutamine, and glutamate were conside rably higher in the AI-82 group than in the Proteamin12 group, and the se differences were also accompanied by a decrease in the plasma branc hed-chain amino acid (BCAA) (leucine, isoleucine, and valine) levels i n the AI-82 group. The high levels of muscle glutamine concentration i n the AI-82 group were investigated in connection with the high use of exogenous branched-chain amino acids.