title: Oxidative DNA damage estimated by oxo8dG in the liver of guinea-pigs supplemented with graded dietary doses of ascorbic acid and alpha-tocopherol.
abstract: Dietary antioxidants may influence cancer risk and aging by modifying oxidative damage. The effect of graded dietary doses of the antioxidant vitamins C and E on oxidative DNA damage was studied in the liver of guinea-pigs under normal conditions. Like human beings, guinea-pigs cannot synthesize ascorbate and alpha-tocopherol. In one experiment, three groups of 6-8 guinea-pigs were fed diets containing 15 mg of vitamin E/kg chow and three different amounts of vitamin C (33,660 or 13,200 mg/kg) for 5 weeks. In a second experiment, three groups of seven guinea-pigs were fed diets containing 660 mg of vitamin C/kg and three different amounts of vitamin E (15, 150 or 1500 mg/kg) for 5 weeks. The three graded levels of each vitamin respectively represent marginal deficiency, an optimum supplementation and a megadose. Oxidative damage to liver DNA was estimated by measuring 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo8dG) referred to deoxyguanosine (dG) by means of high-performance liquid chromatography with simultaneous electrochemical-coulometric and ultraviolet detection. The level of ascorbate in the liver was 0.034 +/- 0.051, 1.63 +/- 1.06 and 1.99 +/- 0.44 micromol/g in the low, medium and high dose ascorbate groups (59-fold variation). The liver concentration of alpha-tocopherol was 28 +/- 11, 63 +/- 18 and 187 +/- 34 nmol/g in the low, medium and high dose alpha-tocopherol groups (7-fold variation). The level of oxo8dG in the liver DNA was 1.89 +/- 0.32, 1.94 +/- 0.78 and 1.93 +/- 0.65 per 10(5) dG in the low, medium and high dose ascorbate groups (no effect: P > 0.05). In the low, medium and high dose alpha-tocopherol groups oxo8dG level in the liver DNA was 2.85 +/- 0.70, 2.74 +/- 0.66 and 2.61 +/- 0.92 per 10(5) dG (no effect: P > 0.05). It is concluded that even very large variations in the content of the antioxidant vitamins C and E in the diet and liver have no influence on the steady-state level of oxidative damage to guanine in the liver DNA of normal unstressed guinea-pigs.
authors.affiliation: Department of Pharmacology, Panum Institute, University of Copenhagen, Copenhagen N, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Cadenas
authors.forename: G
authors.initials: G
authors.lastname: Barja
authors.forename: H E
authors.initials: HE
authors.lastname: Poulsen
authors.forename: S
authors.initials: S
authors.lastname: Loft
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D001205:Ascorbic Acid / Q000008:administration & dosage*; D018890:Chemoprevention; D004247:DNA / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000032:analysis; D004032:Diet; D006168:Guinea Pigs; D008099:Liver; D008297:Male; D010084:Oxidation-Reduction; D014810:Vitamin E / Q000008:administration & dosage*
chemical_list: D014810:Vitamin E; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D003849:Deoxyguanosine; D001205:Ascorbic Acid