TISSUE-SPECIFIC MUTATIONAL SPECTRA OF 2-AMINO-3,4-DIMETHYLIMIDAZO[4,5-F]QUINOLINE IN THE LIVER AND BONE-MARROW OF LACI TRANSGENIC MICE

2-Amino-3,4-dimethylimidazo[4,5-f]quinol (MeIQ) is a food-borne hetero cyclic amine, so clarification of its mutational spectrum is important for evaluation of its carcinogenic risk to humans, The mutational spe ctrum of MeIQ was investigated in the liver and bone marrow of transge nic mice carrying the lad gene, By PCR-single-strand conformation poly morphism analysis and sequencing of the lad gene, 81 and 61 mutations were identified in 80 and 59 mutants obtained from the liver and bone marrow respectively of three transgenic mice given food containing 300 p.p.m. MeIQ, In the liver, G-->T transversions were the most frequent , accounting for 46% of the total mutations, followed by G-->A transit ions (25%), In the bone marrow, four types of mutations, G-->T transve rsions, G-->A transitions, complex mutations and one base deletions, e ach accounted for 21-23% of the total mutations, Of the total mutation s, 10% were found at nucleotide 92 in the liver and at nucleotide 222 in the bone marrow, Analysis of 27 and 13 mutants from the liver and b one marrow respectively of control mice showed frequent G-->A transiti ons at CpG sites, These findings suggest a tissue-specific mechanism o f mutagenesis.