No abstract

This paper describes the development of a relatively rapid single-dose model for induction of lung adenomas in female A/J mice by the tobacco-specific nitrosamine 4-(methylnitros-amino)-1-(3-pyridyl)-1-butanone (NNK). Mice maintained on AIN-76A semi-synthetic diet were given a single i.p. dose of 2.5, 5 or 10 mumol NNK in saline and killed 3-7 months later. Maximum lung tumor induction, measured by lung tumors per mouse (tumor multiplicity), occurred in 3.5 months. There was no significant increase in tumor multiplicity between 3.5 and 7 months. Four months after treatment, numbers of lung tumors per mouse were 11.9 +/- 1.0 (10 mumol NNK), 3.6 +/- 0.4 (5 mumol), 0.9 +/- 0.4 (2.5 mumol) and 0.07 +/- 0.1 (saline). Lung tumor multiplicity in mice treated with a single dose of 10 mumol NNK and maintained on AIN-76A diet was significantly higher (8.3 +/- 0.5) than in mice treated with NNK and maintained on NIH-07 diet (2.5 +/- 0.3). The results of this study establish a useful bioassay for identification of compounds that can modify NNK-induced lung tumorigenesis.

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.

No abstract

The distribution and metabolism of phenethyl isothiocyanate (PEITC), a naturally occurring anticarcinogen, was investigated in A/J mice. Mice were administered 5 mumol of [14C]PEITC (2 microCi/mouse) by gavage and killed at 1, 2, 4, 8, 24, 48 or 72 h after dosing. Radioactivity present in the spleen, heart, liver, lung, kidney, brain, urine and feces was measured. Lung, the target tissue of PEITC inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) lung tumorigenesis, showed maximum radioactivity between 4 and 8 h after dosing, suggesting this time period would be optimal for maximal inhibition by PEITC in A/J mice. Approximately 50% of the total radioactivity was excreted within 24 h after dosing with nearly 80% of radioactivity found in urine and feces at 72 h. Two metabolites were isolated by reverse-phase HPLC from urine of mice treated with PEITC. The identities of these metabolites were determined by comparison with synthetic standards and by NMR and MS. The major metabolite was a cyclic mercaptopyruvic acid conjugate, whereas the minor metabolite was an N-acetylcysteine conjugate. Approximately 25% of the administered dose of PEITC was excreted as the cyclic mercaptopyruvic acid conjugate and 10% as the N-acetylcysteine conjugate. These results suggest that urinary metabolites of PEITC may provide potentially useful dosimeters for this natural anticarcinogen.