Inhibition of aflatoxin B1 -hepatocarcinogenesis in rats by β-naphthoflavone

Effects of β-naphthonflavoe (βNF) on the activity of hepatic microsomal aflatoxin B1 (AFB1)-4-hydroxylase - the cytochrome P-450-dependent enzyme system which catalyzes the metabolism of AFB1 to AFM1 - and on AFB1 induced in vivo hepatocarcinogenesis were investigated in weanling male Fischer rats. A single i.p. injection of βNF in doses of 20 mg/kg and 150 mg/kg induced AFB1 -4-hydroxylase 3- and 4-fold, respectively, 48 h post injection. Feeding of diet containing 0.01% βNF for a period of 9-weeks induced AFB1 ∼2-fold. AFB1, given by intubatlon in a dose of 25 μg five times/week for 8 weeks, produced 42 weeks later a 100% incidence of liver lesions (neoplastic foci, nodules or tumors), but feeding βNF in diet at a con centration of 0.015% for one week prior to and during the 8 weeks of AFB treatment inhibited AFB1 hepatocarcino genesis by -7%. These results are in accord with the suggestion that AFB1 induction may be associated with the inhibition of AFB1 carcinogenesis, possibly occurring as a consequence of accelerated detoxi-fication of AFB1 via its conversion to AFM1