Effects of potassium ethylxanthogenate on nitrosodiethylamine-induced DNA damage and on liver carcinogenesis.

BD-6 rats were injected with 80 mg/kg N-nitroso-diethylamine weekly for 10 weeks. Addition of 270 mg/kg potassium ethylxanthogenate weekly reduced significantly the number of rats developing NDEA-induced malignant liver tumors. Ethylxanthogenate decreased the total number of liver tumors induced by the carcinogen to 6 as compared to a total of 29 neoplasms in animals treated only with NDEA. In acute experiments potassium ethylxanthogenate markedly decreased the exhalation of 14CO2 derived from 14C-NDEA. The amount of the nonmetabolized carcinogen increased in the urine of ethylxanthogenate protected rats only 4% of the given dose. Initial DNA damage, single strand breaks and alkali-labile sites, was determined by alkaline sucrose gradients and in protected animals was minimal for at least 24 hours after NDEA administration. It appears that the production of less initial DNA damage may be important for the further course of liver carcinogenesis induced by relatively large doses of nitrosodiethylamine.