ANALYSIS OF N-ALKYLATED AMINO-ACIDS IN HUMAN HEMOGLOBIN - EVIDENCE FOR ELEVATED N-METHYLVALINE LEVELS IN SMOKERS

To investigate the contribution of cigarette smoking to the levels of N-methylvaline and N-hydroxyethylvaline in hemoglobin we analyzed samp les from 32 smokers and 37 nonsmokers. The average background levels o f the nonsmoking individuals were determined to be 1175 +/- 176 pmol N -methylvaline/g globin, ranging from 722 to 1516 pmol/g globin, and 46 +/- 12 pmol N-hydroxyethylvaline/g globin, ranging from 19 to 64 pmol /g globin. A significant correlation (P < 0.001) was found between bot h amino acids and the amount of cigarettes smoked per day, with an inc rease of 42 pmol N-methylvaline/g globin/cigarette per day and 11 pmol N-hydroxyethylvaline/g globin/cigarette per day. No influence of age, sex, and occupational exposure was observed. Furthermore, the levels of N-hydroxyethylvaline and N-methylvaline correlated for smokers but not for nonsmokers, indicating cigarette smoking as a common source fo r both adducts. To our knowledge, this is the first time N-methylvalin e levels are reported to differ significantly between smokers and nons mokers in the general population. Especially the analysis of N-methylv aline following low-level exposures to methylating agents should there fore take into consideration the influence of individual smoking habit s. Additionally, the results of our study confirm the reliability of N -hydroxyethylvaline as an indicator of individual cigarette consumptio n. We successfully applied a new calibration technique to the analysis of N-hydroxyethylvaline, introducing a commercially available and wel l-defined dipeptide standard. The observed levels of N-hydroxyethylval ine in the samples are in line with those reported in the literature a nd verify the applicability of our calibration method.