The influence of various factors on the methylation of DNA by the oesophageal carcinogen N-nitrosomethylbenzylamine. I. The importance of alcohol.

Alcohol appears to be a predisposing factor for the high incidence of oesophageal cancer in Western France. Therefore, we have investigated the influence of ethanol on the alkylation of DNA by a carcinogen which reacts selectively with oesophageal tissue. Female Wistar rats (approximately 80 g) received a single i.v. injection of N-nitroso-[methyl-14C]benzylamine (2.5 mg/kg body weight). Four hours after injection of the carcinogen, methylation of purine bases in the DNA isolated from various organs was measured. We found that pretreating the rats with alcohol (45-69 micrograms/day/kg) for a period of 3-4 weeks leads to an enhancement of DNA methylation in the oesophagus. An increased amount of methylated purine base was also noted in lung DNA. In contrast, a reduction in the methylation rate of liver DNA was observed.