Aflatoxin B-1 induced lacI mutation in liver and kidney of transgenic mice C57BL/6N: Effect of phorone

Transgenic C57BL/6N mice containing a lambda shuttle vector carrying a lacI target and an alpha-lacZ reporter gene have been used to study the modulating effect of phorone, a glutathione-depleting agent, on the mutagenic activity of aflatoxin B-1 (AFB(1)) in vivo. Animals were treated with AFB(1) (8 mg/kg) for four consecutive days and the animals sacrificed 21 days after the last treatment. Treatment with AFB(1) alone did not result in a significant increase in mutation frequency in the liver and kidney. When the animals were treated with phorone 4 h prior to treatment with AFB(1) a significant increase in mutation frequency was observed in the liver (4-fold) and kidney (1.5-fold). Phorone treatment did not increase the AFB(1)-induced mutation frequency in the lung and intestine. DNA sequence analyses of 30 independent clones isolated from the liver of AFB(1)-treated animals showed that G:C-->T:A transversion (60%) was the predominant mutational event. Mutations within the lad gene could not be detected in seven of 30 mutants, The mutations were randomly distributed throughout the coding sequences of the lacI gene and no hotspots for the mutations were observed, However, codons 86 and 928 appeared to be major sites for mutation, The study shows that the transgenic mouse in vivo mutagenesis model can be used to study the influence of effect-modifying compounds on the mutagenic activity of known carcinogens.