title: Persistent and heritable structural damage induced in heterochromatic DNA from rat liver by N-nitrosodimethylamine.
abstract: Analysis, by benzoylated DEAE-cellulose chromatography, has been made of structural change in eu- and heterochromatic DNA from rat liver following administration of the carcinogen N-nitrosodimethylamine (10 mg/kg body weight). Either hepatic DNA was prelabeled with [3H]thymidine administered 2-3 weeks before injection of the carcinogen or the labeled precursor was given during regenerative hyperplasia in rats treated earlier with N-nitrosodimethylamine. Following phenol extraction of either whole liver homogenate or nuclease-fractionated eu- and heterochromatin, carcinogen-modified DNA was examined by stepwise or caffeine gradient elution from benzoylated DEAE-cellulose. In whole DNA, nitrosamine-induced single-stranded character was maximal 4-24 h after treatment, declining rapidly thereafter; gradient elution of these DNA preparations also provided short-term evidence of structural change. Following incubation of purified nuclei with micrococcal nuclease, 10-12% of labeled DNA was solubilized (eu-chromatin) by 1.0 unit of micrococcal nuclease (5 mg of DNA)-1 mL-1 after 9 min. In prelabeled animals, administration of N-nitrosodimethylamine caused a marked fall in the specific radioactivity of solubilized DNA, while that of sedimenting DNA was not affected. Caffeine gradient chromatography suggested short-term nitrosamine-induced structural change in euchromatic DNA, while increased binding of heterochromatic DNA was evident for up to 3 months after carcinogen treatment. Preparations of newly synthesized heterochromatic DNA from animals subjected to hepatectomy up to 2 months after carcinogen treatment provided evidence of heritable structural damage. Carcinogen-induced binding of heterochromatic DNA to benzoylated DEAE-cellulose was indicative of specific structural lesions whose affinity equalled that of single-stranded DNA up to 1.0 kilobase in length.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000187:drug effects*; D004249:DNA Damage; D004128:Dimethylnitrosamine / Q000494:pharmacology*; D005260:Female; D006570:Heterochromatin / Q000187:drug effects*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D006570:Heterochromatin; D004247:DNA; D004128:Dimethylnitrosamine