A detailed study of the urinary metabolites of N'-nitrosonornicotine has been performed, employing a simple high pressure liquid chromatographic method. The percentage excretion of the principal urinary metabolites was determined over a dose range of 3-300 mg/kg in the F-344 rat, as follows: 4-hydroxy-4-(3-pyridyl)butyric acid (37.1-53.3%, respectively, of the dose), N'-nitrosonornicotine-I-N-oxide (6.7-10.7%), norcotinine (3.2-5.1%), 4-oxo-4-(3-pyridyl)butyric acid (31.1-12.8%), N'-nitrosonornicotine (3.3-5.2%). In the strain A mouse and Syrian golden hamster, the urinary metabolites were qualitatively similar to those observed in the F-344 rat. The interrelationships of the various metabolites of N'-nitrosonornicotine which have been observed in vitro and in vivo were established. The in vitro metabolites resulting from 2'-hydroxylation by liver microsomes, myosmine and 4-hydroxy-I-(3-pyridyl)-1-butanone were converted, by the F-344 rat, primarily to 4-oxo-4-(3-pyridyl)butyric acid as a urinary metabolite. The in vitro metabolite resulting from 5'-hydroxylation by liver microsomes, 2-hydroxy-5-(3-pyridyl)tetrahydrofuran, gave 4-hydroxy-4-(3-pyridyl)butyric acid as its major urinary metabolite, apparently via 5-(3-pyridyl)-tetrahydrofuran-2-one. N'-nitrosonornicotine-I-N-oxide, the remaining major in vitro metabolite, was excreted to a large extent unchanged in F-344 rat urine. The urinary metabolites from 2'-hydroxylation and 5'-hydroxylation of N'-nitrosonornicotine, 4-oxo-4-(3-pyridyl)butyric acid and 4-hydroxy-4-(3-pyridyl)butyric acid, respectively, were not formed from the in vivo metabolite norcotinine and were ot interconverted significantly by the F-344 rat. Thus, these metabolites appear to be reliable indicators for the two possible in vivo alpha-hydroxylations of N'-nitrosonornicotine.

No abstract

Various factors which might contribute to the presence of or reflect on the formation of N'-nitrosonornicotine (NNN) or related nitrosamines in tobacco were studied. Using high-performance liquid chromatography (HPLC), the E- and Z-isomers of NNN were clearly separated and the rates of interconversion were determined. The E/Z ratio in tobacco approximated that observed in solution at similar pH and temperature. The influence of curing and stalk position on NNN levels in tobacco was determined. NNN was not detected in green tobacco but was detected in air-cured leaves from the same crop. No significant correlation was observed among stalk position and NNN levels in one variety of bright tobacco. Since NNN may derive from nicotine, two new nitrosamines, a nitrosamino ketone and a nitrosamino aldehyde, which could theoretically arise from nicotine, were synthesized. Analysis of tobacco for these components is currently in progress

No abstract