COMPARISON OF PULMONARY DNA ADDUCT LEVELS, MEASURED BY P-32 POSTLABELING AND ARYL-HYDROCARBON HYDROXYLASE-ACTIVITY IN LUNG PARENCHYMA OF SMOKERS AND EX-SMOKERS

In order to compare pulmonary DNA adducts and aryl hydrocarbon hydroxylase (AHH) activity, we have measured these two parameters in non-neoplastic surgical lung parenchymal samples from four ex-smokers and 19 smokers, out of 20 patients operated for lung cancer, and three for non-malignant lung diseases. DNA adducts were determined by scintillation counting after P-32-postlabelling analysis. The microsomal fractions of the same lung specimen were assayed for AHH activity by a fluorometric method. Autoradiograms of DNA adducts found in lungs of smokers revealed two distinct diagonal radioactive zones that were absent in ex-smokers. The smokers had significantly higher levels (1.68-13.4 DNA adducts/10(8) nucleotides; mean +/- SD 5.38 +/- 3.19) than ex-smokers (0.23-2.21; 1.09 +/- 0.84). AHH activity in smokers ranged from 0.01 to 0.69 pmol/min/mg. This activity was significantly (P < 0.05) higher in smokers (0.26 +/- 0.26) who had smoked until 1 week before surgery than in those who had stopped smoking for > 7 days (0.11 +/- 0.11). A positive linear correlation between DNA adduct levels and AHH activity (r = 0.69; P < 0.001; n = 19) was found in smokers. This relationship could explain why AHH inducibility appears to be a crude marker for lung cancer risk in smokers.