Dietary arginine influences Rous sarcoma growth in a major histocompatibility B complex progressor genotype.

L-Arginine (L-Arg) can serve as a substrate for the production of reactive nitrogen intermediates. One of these metabolites, nitric oxide, has been shown to possess significant antitumor properties in vitro. To investigate the importance of this system in vivo, we have examined the dietary L-Arg host tumor interaction in the chicken. Since chickens are incapable of de novo L-Arg synthesis, concentration of this amino acid is readily controlled by diet. Line UNH 105 New Hampshire chickens having the major histocompatibility complex genotype, B24/B24, were used to study in vivo effects of dietary L-Arg on Rous sarcoma growth. After 5 weeks on a standard diet, 119 chicks were fed either a basal (0.92% L-Arg) diet or a high arginine (2.40% L-Arg) diet. One week later, chicks were wing-web inoculated with subgroup A Rous sarcoma virus. Tumor growth was monitored weekly for 12 weeks after inoculation. Plasma L-Arg levels and body weights from birds on each dietary treatment were analyzed. Neither body weight gains nor latent period for tumor development was affected by diet. However, plasma L-Arg levels were significantly different between dietary treatments (basal, 0.245 +/- 0.01 mumol/ml; high, 0.738 +/- 0.03 mumol/ml). In addition, mean tumor size scores were significantly (P less than 0.05) lower over time in chickens fed the high L-Arg diet. The results suggest that dietary L-Arg in excess of the amount required for growth reduces tumor load.