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 in vivo in livers and kidneys of rats were investigated. Male F344 rats were treated with 1 mg/kg AFBI by i.p. administration and nucleic acids isolated 2 h post dosing. Animals were fed a semipurifled diet supplemented with either 0.5% EQ, 0.45% BHT, 0.45% BHA or 0.1% oltipraz for 2 weeks prior to AFBI treatment. Analysis of nucleic acid bases by h.p.l.c. showed that several AFB metabolite-DNA adducts were formed in both tissues. The principal and related adducts of 8,9-dlhydro-8-(N² guanyl)-9-hydroxyaflatoxin represented {reversed tilde}80-90% of all adducts in both tissues and in all treatment groups. However, inclusion of the antioxidants in the diet resulted in substantial reductions in overall AFB modified DNA levels. EQ, BHT, BHA and oltipraz reduced the covalent binding of AFB to liver DNA by 91, 85, 65 and 76% and to kidney DNA by 80, 35, 62 and 64%, respectively. Concordantly, the specific activities of hepatic enzymes of presumed importance to AFB₁ detoxification, epoxide hydrase, and glycuronyl and glutathione transferases were significantly elevated by all antioxidants. Reduced glutathione levels were unchanged except by oltipraz, although activities of enzymes contributing to the maintenance of reduced gluta-thione pools, 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 of DNA binding by AFB₁ and the induction of hepatic glutathione S-transferase activities by the four antioxidants.