ALKYLATION AND OXIDATIVE-DNA DAMAGE REPAIR ACTIVITY IN BLOOD LEUKOCYTES OF SMOKERS AND NONSMOKERS

The levels of 3 DNA repair enzymes involved in alkylation and oxidativ e DNA damage repair in human peripheral blood leukocytes were measured in 20 smokers and 17 non-smokers. No differences in O6-alkylguanine-D NA-alkyltransferase (AGT) activity were found between the 2 groups and the AGT distribution within the population appeared to be unimodal. I n contrast, the mean activities of both the methylpurine (MeP)- and th e 2-6-diamino-4-hydroxy-SN formamidopyrimidine (FaPy)-DNA glycosylases were higher in the smokers, although only the difference between the MeP-DNA glycosylase means was statistically significant. The standard deviations of these 2 enzymes were also higher in the smokers. The MeP -DNA glycosylase activity showed a bimodal distribution when all subje cts were considered. This may in part be due to the smoking habit; 83% of the subjects with enzyme activities higher than 500 fmoles/mg prot ein were current smokers, whilst 85% of the non-smokers had lower enzy me activities. However, if the smokers were considered separately, a b imodal distribution of this enzyme activity could still be observed. N o strong correlation was observed between enzyme activity and age, alt hough the slopes of the regression lines of enzyme activity on age wer e all negative. The relationship between enzyme activities was studied by bivariate distribution and a strong correlation was only found bet ween the MeP-DNA glycosylase and the FaPy-glycosylase, with the highes t values of both enzyme activities being observed in the smokers and t he lowest in the non-smokers. Our results suggest that the activity of certain DNA repair enzymes can be modulated by environmental exposure . (C) 1993 Wiley-Liss, Inc.