Abstract: BACKGROUND AND AIM: To investigate the effects of oxidative stress induced by smoking by quantifying various biomarkers of oxidative DNA damage, lipid peroxidation and antioxidative defense mechanisms. MATERIALS AND METHODS: Sixty male smokers and thirty male nonsmokers aged 18-25 were recruited and divided into two groups.8-OHdG in 24 h urine was analysed by HPLC-ECD; peripheral lymphocyte DNA strand breaks by comet assay; MDA, ACON and PP in 24 h urine were analysed by HPLC-UV and plasma antioxidant enzymes were assessed. RESULTS: 8-OHdG and DNA strand breaks were significantly greater by 185％ and 97％,respectively, in 60 smokers than in 30 nonsmokers. MDA, ACON and PP in urine were significantly higher than nonsmokers(P<0.01). Superoxide dismutase(SOD), glutathione peroxidase (GPX), and catalase were significantly lower by 15％,10％,and 9％, respectively, in smokers than nonsmokers(P≤0.01). CONCLUSION: Oxidative stress imposed by cigarette smoking had an impact upon certain pathways involved in DNA damage, lipid peroxidation and antioxidative defense system.

Key words: smoking, DNA damage, lipid peroxidation, antioxidative enzymes, reactive oxygen species