Re-evaluation of the effect of smoking on the methylation of N-terminal valine in haemoglobin

In view of the established extrapulmonary cancer sites targeted by smoking a multiplicity of compounds and mechanisms might be involved. It has been d ebated that smoking caused increased incidence of N-methylvaline at the N-t erminus of haemoglobin. Because this could indicate a relevance of methylat ing nitrosamines in tobacco smoke, data are presented from an industrial co hort of 35 smokers and 21 non-smokers repeatedly monitored between 1994 and 1999. In general, N-methylvaline adduct levels in haemoglobin of smokers w ere approximately 50% higher than those of non-smokers. The smoking-induced methylation of haemoglobin is likely to be caused by dimethylnitrosamine ( N-nitroso-dimethylamine), a major nitrosamine in side-stream tobacco smoke. The biomonitoring data emphasise the potential value of N-methylvaline as a smoking-related biomarker and call for intensified research on tobacco sm oke compounds that lead to macromolecular methylation processes.