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)

• Authors: E J Ward, B W Stewart
• Journal: Biochemistry (Biochemistry) Vol. 26 Issue 6 Pg. 1709-17 (Mar 24 1987) ISSN: 0006-2960 [Print] United States
• PMID: 3593686 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Heterochromatin
• DNA
• Dimethylnitrosamine

Topics

• Animals
• Cell Nucleus (drug effects, metabolism)
• DNA (drug effects)
• DNA Damage
• Dimethylnitrosamine (pharmacology)
• Female
• Heterochromatin (drug effects)
• Kinetics
• Liver (drug effects, metabolism)
• Rats
• Rats, Inbred Strains