Effect of chronic administration of dimethylnitrosamine on the excision of O6-methylguanine from rat liver DNA

Abstract

Rats were exposed chronically to unlabelled N,N-dimethylnitrosamine (25 ppm in the drinking water) then given a single dose of N-[3H]methyl-N-nitrosourea (10 mg/kg body weight). The rates of loss of tritium-labeled 7-methylguanine, O6-methylguanine and 3-methyladenine from the liver DNA in control and dimethylnitrosamine-treated rats were found not to be significantly different. Thus, under the conditions used, inhibition of the O6-methylguanine excision repair system does not seem to be a factor in the induction of liver tumours by chronic DMN application.