title: Tobacco-specific nitrosamines and their pyridine-N-glucuronides in the urine of smokers and smokeless tobacco users.
abstract: Tobacco-specific nitrosamines are believed to play a significant role as causes of cancer in people who use tobacco products. Whereas the uptake of one tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, has been shown by analysis of its metabolites in urine, there are no published studies on urinary levels of N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), and N'-nitrosoanabasine (NAB) or their metabolites in human urine. We developed a method for quantitation of NNN, NAT, NAB, and their pyridine-N-glucuronides NNN-N-Gluc, NAT-N-Gluc, and NAB-N-Gluc in human urine. Total NNN (NNN plus NNN-N-Gluc) was assayed using 5-methyl-N'-nitrosonornicotine as internal standard. Urine was treated with beta-glucuronidase. Following solvent partitioning and solid-phase extraction, total NNN was determined using gas chromatography with nitrosamine-selective detection. Total NAT and total NAB were quantified in the same samples. Separate quantitation of NNN and NNN-N-Gluc was accomplished by extraction of the urine with ethyl acetate before beta-glucuronidase hydrolysis; NNN was analyzed in the ethyl acetate extract, and after enzyme treatment, NNN released from NNN-N-Gluc was quantified in the extracted urine. Separate analyses of NAT, NAT-N-Gluc, NAB, and NAB-N-Gluc proceeded similarly. Analyte identities were confirmed by gas chromatography-tandem mass spectrometry. Mean levels of total NNN, NAT, and NAB in the urine of 14 smokers were (pmol/mg creatinine) 0.18 +/- 0.22, 0.19 +/- 0.20, and 0.040 +/- 0.039, respectively, whereas the corresponding amounts in the urine of 11 smokeless tobacco users were 0.64 +/- 0.44, 1.43 +/- 1.10, and 0.23 +/- 0.19, respectively. Pyridine-N-glucuronides accounted for 59% to 90% of total NNN, NAT, and NAB. The results of this study show the presence of NNN, NAT, NAB, and their pyridine-N-glucuronides in human urine and provide a quantitative method for application in mechanistic and epidemiologic studies of the role of tobacco-specific nitrosamines in human cancer.
authors.affiliation: The Cancer Center, University of Minnesota, Mayo Mail Code 806, 420 Delaware Street Southeast, Minneapolis, MN 55455, USA.
authors.forename: Irina
authors.initials: I
authors.lastname: Stepanov
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Hecht
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000378:metabolism*; D002849:Chromatography, Gas / Q000379:methods*; D003367:Cotinine / Q000652:urine; D003404:Creatinine / Q000652:urine; D020719:Glucuronides / Q000652:urine*; D006801:Humans; D009602:Nitrosamines / Q000652:urine*; D012907:Smoking / Q000652:urine*; D014030:Tobacco, Smokeless / Q000378:metabolism*
chemical_list: D002273:Carcinogens; D020719:Glucuronides; D009602:Nitrosamines; D003404:Creatinine; D003367:Cotinine