Modification of aflatoxin B1 binding to DNA in vivo in rats fed phenolic antioxidants, ethoxyquin and a dithiothione

The effects of dietary administration of 3,5-di-tert-butyl-4-hydroxytoluene (BHT), 2(3)-tert-butyl-4-hydroxyanisole (BHA),ethoxyquin (EQ) and 5-(2-pyrizinyl)-4-methyl-1,2- dithiol-3-thione(oltipraz) on aflatoxin B₁ (AFB₁) - DNA adduct formation invivo in livers and kidneys of rats were investigated. Male F344rats were treated with 1 mg/kg AFBI by i.p. administration andnucleic acids isolated 2 h post dosing. Animals were fed a semipurifleddiet supplemented with either 0.5% EQ, 0.45% BHT, 0.45% BHAor 0.1% oltipraz for 2 weeks prior to AFBI treatment. Analysisof nucleic acid bases by h.p.l.c. showed that several AFB metabolite-DNAadducts were formed in both tissues. The principal and relatedadducts of 8,9-dlhydro-8-(N² guanyl)-9-hydroxyaflatoxin represented80-90% of all adducts in both tissues and in all treatment groups.However, inclusion of the antioxidants in the diet resultedin substantial reductions in overall AFB modified DNA levels.EQ, BHT, BHA and oltipraz reduced the covalent binding of AFBto liver DNA by 91, 85, 65 and 76% and to kidney DNA by 80,35, 62 and 64%, respectively. Concordantly, the specific activitiesof hepatic enzymes of presumed importance to AFB₁ detoxification,epoxide hydrase, and glycuronyl and glutathione transferaseswere significantly elevated by all antioxidants. Reduced glutathionelevels were unchanged except by oltipraz, although activitiesof enzymes contributing to the maintenance of reduced gluta-thionepools, glutathione reductase and glucose-6- phosphate dehydrogenase,were elevated in most treatment groups. An excellent correlation(r = 0.95) was observed between the degree of inhibition ofDNA binding by AFB₁ and the induction of hepatic glutathioneS-transferase activities by the four antioxidants.