Species and Organ Differences in DNA Adduct Formation and Repair after Treatment with 4‐Hydroxyaminoquinoline 1‐Oxide

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Abstract
4‐Hydroxyaminoquinoline 1‐oxide (4HAQO) demonstrates obvious organotropic and species specificity in its carcinogenesis and the present investigation concerns 4HAQO DNA adduct formation and repair as studied in various organs of four animal species (rats, mice, guinea pigs and hamsters). Three hours after an iv injection of 10 mg per kg body weight of tritium‐labeled 4HAQO, the major organs were removed and used for assessment of label incorporation in the DNA. The results showed that the DNA binding levels generally correlated well with the reported species and organ specificity of 4HAQO tumorigenesis. For example, rats showed highest DNA binding in the pancreas and kidney, major target organs. The levels of DNA binding in the liver were invariably low in all 4 animal species, in agreement with the lack of hepatocarcinogenicity associated with 4HAQO exposure. A clear relationship between DNA adduct formation and carcinogen dose was also found after treatment of mice with 4HAQO at doses of 1, 5, 10 and 20 mg per kg body weight in all tissues (pancreas, kidney and lung) except for the liver. Comparison of DNA repair processes in rats, a highly susceptible species, and hamsters, a resistant species in terms of 4HAQO carcinogenicity, revealed highest formation and slowest removal of adducts in the target organs of the rat. In the hamster organs and the rat lung and liver, DNA adduct formation was generally low and in the case of elevation in the initial phase, quickly removed.

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