N-Methylcarbamoyl-lysine adduct in globin: a new metabolic product and potential biomarker of N, N-dimethylformamide in humans.
Metabolism of the solvents N,N-dimethylformamide (DMF) and N-methylformamide (MF) results in the formation of N-methylcarbamoyl adducts at the N-terminal valine and lysine in blood protein globin, of which the lysine adduct has so far only been reported in rats given high doses of both solvents [Mráz, J., Simek, P., Chvalová, D., Nohová, H., Smigolová, P., 2004. Studies on the methyl isocyanate adducts in globin. Chem. Biol. Interact. 148, 1-10]. Here we examined whether the lysine adduct is produced, and accessible to analysis, in humans occupationally or experimentally exposed to DMF. Globin from exposed subjects (n=35) and unexposed controls (n=5) was analyzed by two methods. Edman degradation was used as a sensitive reference method to measure the valine adduct by converting it to 3-methyl-5-isopropylhydantoin (MVH). The MVH levels in globin of the exposed subjects were in the range of 1-441 nmol/g, in controls <1 nmol/g. The principal method of globin analysis consisted of enzymatic hydrolysis with pronase to release free N(epsilon)-(N-methylcarbamoyl)lysine (MLU) and N-methylcarbamoylvaline (MVU), which were determined by HPLC/MS/MS, with no clean-up or preconcentration steps needed. For MLU, the parent and product ions were m/z 204-->173, and the limit of detection was approximately 5 nmol/g globin. MLU was found in most globins from the exposed subjects but not in the controls. A close correlation between the MLU and MVH levels (nmol/g) was observed: MLU=7+0.48 MVH (R(2)=0.84, n=32). In conclusion, MLU can be easily measured in globin of workers exposed to DMF. The findings also indicate a long-term persistence of MLU in the human body, and consequently, its potential as a biomarker of chronic exposure to DMF.
Mráz
J
J
Centre of Occupational Health, National Institute of Public Health, Srobárova 48, 100 42 Prague 10, Czech Republic. jmraz@szu.cz
Cimlová
J
J
Stránský
V
V
Nohová
H
H
Kicová
R
R
Simek
P
P
D015415:Biomarkers; D004126:Dimethylformamide / Q000378:metabolism*; D005914:Globins / Q000378:metabolism*; D006801:Humans; D006827:Hydantoins / Q000378:metabolism; D008239:Lysine / Q000031:analogs & derivatives / Q000378:metabolism*; D016273:Occupational Exposure / Q000032:analysis; D011485:Protein Binding
C472969:3-methyl-5-isopropylhydantoin; D015415:Biomarkers; D006827:Hydantoins; D004126:Dimethylformamide; D005914:Globins; D008239:Lysine