Using a transplantable Yoshida sarcoma in a rat model of total parenteral nutrition (TPN), we measured the effectiveness of an arginine-enriched amino acid solution (AI-82) on muscle glutamine concentration and muscle protein synthesis compared with that of a conventional amino acid solution (Proteamin12). After tumor-bearing rats had been given one of two isocaloric TPN regimens for 6 days, [15N]glycine (99 atom %) containing TPN solution was infused into animals at a constant rate of 8 mg of [15N]glycine per hour for 18 hours, after which the liver, skeletal muscle (gastrocnemius muscle), and tumor protein synthesis rates were measured. A significantly increased whole muscle protein synthesis rate was observed in the AI-82 group; there was no difference in the whole liver and tumor protein synthesis rates between the two groups. When each TPN solution was administered for 1 week, muscle concentrations of arginine, ornithine, glutamine, and glutamate were considerably higher in the AI-82 group than in the Proteamin12 group, and these differences were also accompanied by a decrease in the plasma branched-chain amino acid (BCAA) (leucine, isoleucine, and valine) levels in the AI-82 group. The high levels of muscle glutamine concentration in the AI-82 group were investigated in connection with the high use of exogenous branched-chain amino acids.
By using a transplantable Yoshida sarcoma in a rat total parenteral nutrition model, we measured the effectiveness of an arginine-enriched amino acid solution (AI-82) in terms of leucine kinetics and nitrogen balance as indicators of host-tumor nutrition interaction compared with that of a conventional amino acid solution (Proteamin12). When tumor-bearing rats received isocaloric total parenteral nutrition solutions for 7 days, AI-82 significantly improved host nitrogen balance and significantly decreased the tumor-nitrogen trap throughout the experimental period. Leucine kinetics of whole body and tissues were also determined by a 4-hour continuous infusion of each total parenteral nutrition solution containing 14C-leucine. Significantly increased whole-body leucine oxidation (p < .01) without an increase in leucine release from normal tissues was observed in the AI-82 group. Total incorporation of 14C-leucine into whole muscle was significantly elevated (p < .05) without changes in muscle protein degradation in the AI-82 group. In the whole tumor, AI-82 tended to decrease total incorporation of 14C-leucine, but there was no difference in leucine release caused by protein breakdown between the two groups. These findings suggest that AI-82 can improve the nutritional status of the host over that of the tumor.
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