Effect of arginine on the carcinogenicity of 7,12-dimethylbenz[a]-anthracene and N-methyl-N-nitrosourea.

The effects of supplementing a 14% casein diet with 5% L-arginine on rat mammary tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) and N-methyl-N-nitrosourea (MNU) were investigated. Dietary arginine supplementation had no significant effect on food intake or growth. In rats treated with either DMBA or MNU, tumor incidence was not significantly affected, but the number of new tumors appearing each week and the cumulative tumor weight per rat were significantly decreased in rats fed 5% arginine diets. In vitro experiments indicated that arginine had no effect on the enzymatic conversion of DMBA to electrophilic DNA-binding metabolites. The decreased tumorigenicity of both MNU and DMBA in rats given supplemental arginine suggests that this amino acid has an inhibitory effect on stage(s) of chemical carcinogenesis other than bioactivation of procarcinogens.