Dose-dependent persistence of alkylation-induced single stranded regions in rat liver DNA in vivo

Single stranded regions in DNA, presumed to be indicative of DNA repair, may be readily detected in rat liver DNA following injections of nonnecrotizing single doses of methyl methanesulfonate, dimethylnitrosamine and diethylnitrosamine. The present study concerns persistence of such structural defects in vivo, as determined by benzoylated DEAE-cellulose chromatography, in relation to the dose of alkylating agent. For all these agents, the period during which structural damage may be detected is markedly dependent upon dose: prolonged persistence only occurs after the highest dose. The findings, in relation to other data, implicate reaction processes involving the final stages of repair as being critical to prolongation of this type of genomic damage in vivo.