Inhibition by N-acetylcysteine of carcinogen-DNA adducts in the tracheal epithelium of rats exposed to cigarette smoke.

The ability of the aminothiol N-acetylcysteine (NAC) to prevent the formation of carcinogen-DNA adducts in tracheal epithelial cells was investigated in Sprague-Dawley rats exposed whole-body to mainstream cigarette smoke for either 40 or 100 consecutive days. 32P-Postlabelling analyses showed the occurrence of DNA adducts (12.49 adducts/10(8) nucleotides) after 40 days of exposure, with a trend to formation of characteristic diagonal radioactive zones. Total adduct levels were not further enhanced after 100 days of exposure to smoke, although significant changes occurred in the amounts of individual adducts. NAC, given by gavage in the 40 day study and in drinking water in the 100 day study, significantly inhibited the formation of smoke-related carcinogen-DNA adducts in the tracheal epithelium, to such an extent that adduct levels were not significantly higher than those detected in sham-exposed control rats. Together with a variety of other molecular, clastogenicity, metabolic, cytological and histopathological end-points investigated in rodents and with the preliminary evidence arising from a study in humans, these results document the considerable efficacy of oral NAC in inhibiting smoke-related carcinogen-DNA adducts.