title: Tumorigenicity and metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol enantiomers and metabolites in the A/J mouse.
abstract: 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite of the tobacco-specific pulmonary carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), has a chiral center but the tumorigenicity of the NNAL enantiomers has not been previously examined. In this study, we assessed the relative tumorigenic activities in the A/J mouse of NNK, racemic NNAL, (R)-NNAL, (S)-NNAL and several NNAL metabolites, including [4-(methylnitrosamino)-1-(3-pyridyl)but-(S)-1-yl] beta-O-D-gluco-siduronic acid [(S)-NNAL-Gluc], 4-(methylnitrosamino)-1-(3-pyridyl N-oxide)-1-butanol, 5-(3-pyridyl)-2-hydroxytetrahydrofuran, 4-(3-pyridyl)butane-1,4-diol and 2-(3-pyridyl) tetrahydrofuran. We also quantified urinary metabolites of racemic NNAL and its enantiomers and investigated their metabolism with A/J mouse liver and lung microsomes. Groups of female A/J mice were given a single i.p. injection of 20 micromol of each compound and killed 16 weeks later. Based on lung tumor multiplicity, (R)-NNAL (25.6 +/- 7.5 lung tumors/mouse) was as tumorigenic as NNK (25.3 +/- 9.8) and significantly more tumorigenic than racemic NNAL (12.1 +/- 5.6) or (S)-NNAL (8.2 +/- 3.3) (P < 0. 0001). None of the NNAL metabolites was tumorigenic. The major urinary metabolites of racemic NNAL and the NNAL enantiomers were 4-hydroxy-4-(3-pyridyl)butanoic acid (hydroxy acid), NNAL-N-oxide and NNAL-Gluc, in addition to unchanged NNAL. Treatment with (R)-NNAL or (S)-NNAL gave predominantly (R)-hydroxy acid or (S)-hydroxy acid, respectively, as urinary metabolites. While treatment of mice with racemic or (S)-NNAL resulted in urinary excretion of (S)-NNAL-Gluc, treatment with (R)-NNAL gave both (R)-NNAL-Gluc and (S)-NNAL-Gluc in urine, apparently through the metabolic intermediacy of NNK. (S)-NNAL appeared to be a better substrate for glucuronidation than (R)-NNAL in the A/J mouse. Mouse liver and lung microsomes converted NNAL to products of alpha-hydroxylation, to NNAL-N-oxide, to adenosine dinucleotide phosphate adducts and to NNK. In lung microsomes, metabolic activation by alpha-hydroxylation of (R)-NNAL was significantly greater than that of (S)-NNAL. The results of this study provide a metabolic basis for the higher tumorigenicity of (R)-NNAL than (S)-NNAL in A/J mouse lung, namely preferential metabolic activation of (R)-NNAL in lung and preferential glucuronidation of (S)-NNAL.
authors.affiliation: University of Minnesota Cancer Center, Box 806 Mayo, 420 Delaware Street SE, Minneapolis, MN 55455, USA.
authors.forename: P
authors.initials: P
authors.lastname: Upadhyaya
authors.forename: P M
authors.initials: PM
authors.lastname: Kenney
authors.forename: J B
authors.initials: JB
authors.lastname: Hochalter
authors.forename: M
authors.initials: M
authors.lastname: Wang
authors.forename: S S
authors.initials: SS
authors.lastname: Hecht
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced*; D000236:Adenoma / Q000139:chemically induced*; D000818:Animals; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*; D018450:Disease Progression; D005260:Female; D005965:Glucuronates / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity* / Q000652:urine; D008168:Lung / Q000378:metabolism; D008175:Lung Neoplasms / Q000139:chemically induced*; D051379:Mice; D008805:Mice, Inbred A; D008861:Microsomes / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D009602:Nitrosamines / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity* / Q000652:urine; D013047:Specific Pathogen-Free Organisms
chemical_list: C099564:4-((methylnitrosoamino)-1-(3-pyridyl)but-1-yl)beta-omega-glucosiduronic acid; D002273:Carcinogens; D005965:Glucuronates; D009602:Nitrosamines; C051577:4-(methylnitrosoamino)-4-(3-pyridyl)-1-butanol