Characterization of a glucuronide metabolite of 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its dose-dependent excretion in the urine of mice and rats.
Following analysis by reversed-phase HPLC, a previously uncharacterized metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was found in the urine of A/J mice treated with NNK. Treatment with beta-glucuronidase converted the metabolite to a peak that co-eluted with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). Treatment with sulfatase or beta-glucuronidase plus saccharic acid 1,4-lactone did not change the retention time of the metabolite. These data suggested that the unknown metabolite was a glucuronic acid conjugate of NNAL. Upon isolation and purification of larger quantities of the metabolite from the urine of A/J mice, CD-1 mice and F344 rats, 1H and 13C NMR and MS confirmed that the unknown metabolite was 4-(methylnitrosamino)-1-(3-pyridyl)-1-butyl beta-D-glucopyranosiduronic acid (NNAL Glu). To determine the quantitative relationship between NNK dose and NNAL Glu production and to compare the importance of glucuronidation relative to other metabolic pathways, [5-3H]NNK was administered to F344 rats and A/J mice at doses of 500-0.005 mumol/kg. At 500 mumol/kg, NNAL Glu accounted for 22% of the total urinary excretion of NNK in A/J mice, and for 8% in F344 rats 48 h after dosing. The proportions of excreted glucuronide and NNAL decreased with diminishing doses of NNK, yielding undetectable levels of each metabolite in both mice and rats at a dose of 0.005 mumol/kg NNK. Since substantial amounts of metabolites formed via alpha-hydroxylation and N-oxidation pathways were observed at the lower doses of NNK, these data demonstrate that NNAL glucuronidation is a quantitatively unimportant metabolic pathway at low doses of NNK.
Morse
M A
MA
Division of Chemical Carcinogenesis, Naylor Dana Institute for Disease Prevention, American Health Foundation, Valhalla, NY 10595.
Eklind
K I
KI
Toussaint
M
M
Amin
S G
SG
Chung
F L
FL
D000818:Animals; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005965:Glucuronates / Q000652:urine*; D005966:Glucuronidase; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008805:Mice, Inbred A; D009602:Nitrosamines / Q000378:metabolism* / Q000652:urine*; D051381:Rats; D011916:Rats, Inbred F344; D014316:Tritium
D002273:Carcinogens; D005965:Glucuronates; D009602:Nitrosamines; D014316:Tritium; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone; D005966:Glucuronidase