Primary mammary and urinary bladder epithelial cells of the rat, and the human urothelial cell line HCV-29 and mammary cell line MCF-10A were incubated for 3 h with 10 mM hydroxyurea and N-hydroxy-N-acetyl-2-aminofluorene, N-hydroxy-N-acetyl-4-aminobiphenyl or N-hydroxy-3,2'-dimethyl-4-aminobiphenyl. DNA adducts of these carcinogens were detected in the nuclei of all cells, except MCF-10A, semi-quantitatively with a novel immunohistochemical-microdensitometric method. The loss of these adducts in these cells was biphasic and was relatively greater between 0 and 24 h than between 24 and 48 h. The half-life of the adducts of all 3 carcinogens was approximately 20 h. The adduct loss is consistent with repair detected by an unscheduled DNA synthesis system reported previously. These results demonstrate that nonacetylated aromatic amine-DNA adducts can be repaired in the target cells for aromatic amine-induced carcinogenesis.

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