Interindividual Variation in the DNA Binding of Chemical Genotoxins Following Metabolism by Human Bladder and Bronchus Explants

Abstract

The DNA-binding of three chemical carcinogens, benzo(a)pyrene (BP), aflatoxin B1 (AFB) and 2-acetylaminofluorene (AAF) subsequent to their metabolic activation by explant cultures of human bladder and bronchus, tissues has been studied. The tissue specimens, obtained at autopsy, were cultured in serum free medium in a rocking culture system under an atmosphere of 50% 02 — 47% N2 — 3% C02. The epithelial cell DNA binding levels were determined 24 hours following the addition of 1 μM of the tritium labeled hydrocarbon and isolation of the DNA by hydroxylapatite chromatography. Following hydrolysis of the purified DNA, the carcinogen-DNA adducts were analyzed via high pressure liquid chromatography (HPLC). The BP-DNA adducts obtained from both tissues co-chromatographed with adduct standards formed by the reactions of 7,8-dihydroxy-7,8,9,10-tetra- hydrobenzo(a)pyrene at the exocyclic amino nitrogen (N2) of guanine. The AFB-DNA adducts co-chromatographed with adducts found in rat liver in vivo and formed by the attack of 8,9-dihydro-8,9-oxyaflatoxin Bi at the N7 position of guanine. The range of DNA binding inter- individual variation was higher in the bladder than in the bronchus for all three chemicals. Further, weak but significant, correlations between the carcinogen-DNA binding level in explants of the two tissues from the same individual was observed for all three carcinogens. For both human bladder and bronchus there was a significant correlation between BP and AAF DNA binding levels in tissues from the same individual whereas no such significant correlation existed between BP and AFB DNA binding levels. The utility of the explant culture method for measuring interindividual variation with respect to genotoxin metabolism is discussed.