Inhibition of aflatoxin B1 -hepatocarcinogenesis in rats by {beta}-naphthoflavone

Effects of ß-naphthonflavoe (ßNF) on theactivity of hepatic microsomal aflatoxin B₁ (AFB₁)-4-hydroxylase- the cytochrome P-450-dependent enzyme system which catalyzesthe metabolism of AFB₁ to AFM₁ - and on AFB₁ induced in vivohepatocarcinogenesis were investigated in weanling male Fischerrats. A single i.p. injection of ßNF in doses of 20mg/kg and 150 mg/kg induced AFB₁ -4-hydroxylase 3- and 4-fold,respectively, 48 h post injection. Feeding of diet containing0.01% ßNF for a period of 9-weeks induced AFB₁ 2-fold.AFB₁, given by intubatlon in a dose of 25 µg five times/weekfor 8 weeks, produced 42 weeks later a 100% incidence of liverlesions (neoplastic foci, nodules or tumors), but feeding ßNFin diet at a con centration of 0.015% for one week prior toand during the 8 weeks of AFB treatment inhibited AFB₁ hepatocarcinogenesis by -7%. These results are in accord with the suggestionthat AFB₁ induction may be associated with the inhibition ofAFB₁ carcinogenesis, possibly occurring as a consequence ofaccelerated detoxi-fication of AFB₁ via its conversion to AFM₁