DNA Modification by 2‐Amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine in Rats

2‐Amino‐l‐methyl‐6‐pheny]imidazo[4,5‐b]pyridine (PhIP) is the most abundant mutagenic heterocyclic amine by weight in cooked foods. This mutagen was found to produce DNA adducts in all ten tested organs of rats using the (32)P‐postlabeling method. The level of DNA adducts in the pancreas, kidney and liver increased dose‐dependently and feeding tinie‐dependently up to four weeks. When diet containing 0.05% PhIP was given to rats for four weeks, levels of PhIP‐DNA adducts were relatively high in the lung, pancreas and heart, being around 20 per 10(7) nucleotides, and lowest in the liver, being 2.20 per 10(7) nucleotides. Thus, PhIP showed a unique feature in the formation of DNA adducts compared to other mutagenic and carcinogenic heterocyclic amines, which produce the highest level of DNA adducts in the liver.