Effect of butylated hydroxyanisole pretreatment on aflatoxin B1-DNA binding and aflatoxin B1-glutathione conjugation in isolated hepatocytes from rats.
The effect of 2(3)-tert-butyl-4-hydroxyanisole (BHA) pretreatment of rats on both aflatoxin B1 (AFB1)-DNA binding and AFB1-glutathione has been examined with isolated hepatocytes and in intact rats. Young male F344 rats were fed AIN-76A diet with or without 0.75% BHA for 2 weeks. Even though there were no significant differences in either cytochrome P-450 or reduced glutathione contents, there were marked differences in AFB1 metabolism in isolated hepatocytes from these two groups. Thus, at the 33 nM AFB1 level, AFB1-DNA binding was 3-fold higher in control compared to BHA-treated hepatocytes whereas AFB1-glutathione conjugation was 5-fold higher in treated compared to controls. Even at higher AFB1 concentrations (2 and 10 microM), DNA binding was 4-6-fold higher in controls whereas thiol conjugation was 5-9-fold higher in treated compared to control hepatocytes. Addition of 0.5-1.0 mM diethylmaleate did not have any significant effect in control hepatocytes whereas its presence produced about 70-100% increase in DNA binding with 65-80% inhibition of thiol conjugation in treated hepatocytes. Addition of 1 mM styrene oxide caused 75-100% and 4-8-fold increase in AFB1-DNA binding in control and treated hepatocytes, respectively, with corresponding decreases in thiol conjugation. In intact rats, BHA treatment reduced hepatic AFB1-DNA binding to 15% of controls with concomitant increase in biliary excretion of AFB1-reduced glutathione conjugate. It appears that the induced cytosolic GSH S-transferases after BHA treatment of rats play a significant role in inhibiting hepatic AFB1-DNA binding and AFB1 hepatocarcinogenesis presumably by inactivation of the reactive AFB1-epoxide.
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Fels Research Institute, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
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Tsuji
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Gopalan
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Lotlikar
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D016604:Aflatoxin B1; D000348:Aflatoxins / Q000378:metabolism*; D000818:Animals; D002083:Butylated Hydroxyanisole / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism*; D004790:Enzyme Induction; D005978:Glutathione / Q000032:analysis / Q000378:metabolism*; D005982:Glutathione Transferase / Q000502:physiology; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D000348:Aflatoxins; D002083:Butylated Hydroxyanisole; D004247:DNA; D016604:Aflatoxin B1; D005982:Glutathione Transferase; D005978:Glutathione