Smoking-related increase in O6-alkylguanine-DNA alkyltransferase activity in human lung tissue.

O6-Alkylguanine-DNA alkyltransferase (AGAT) activity was determined in macroscopically normal peripheral lung tissues from 122 patients undergoing lung surgery. AGAT activity of smokers was 1.4-fold higher than that of lifetime non-smokers (P = 0.030). Less than one year of abstinence from smoking did not cause a significant decrease in AGAT activity in former smokers, however, longer abstinence resulted in a decrease in AGAT activity to the level detected in lifetime non-smokers. There was no significant difference between levels of AGAT activity in lung cancer and noncancer patients. The results demonstrate that the level of AGAT activity in human peripheral lung tissue is influenced by smoking habits but does not have a diagnostic correlation to lung cancer.