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Nitrosodiphenylamine was tested for induction of DNA single strand breaks in rat hepatocytes and Chinese hamster V 79 cells with the alkaline filter elution assay. While in rat hepatocytes DNA damage was observed, negative results were obtained in V 79 cells. In view of the metabolic capacity of hepatocytes and the chemical structure of nitrosodiphenylamine it seems likely that cytochrome P-450-dependent, reductive denitrosation might be necessary for exerting this effect. Therefore the metabolism of nitrosodiphenylamine was investigated in phenobarbital-induced mouse liver microsomes and some of the metabolites were also tested. One metabolite was identified as diphenylamine whereas the others were identified as a ring-hydroxylated derivative of diphenylamine and its corresponding quinoneimine. Diphenylhydroxylamine which was not detected in the microsomes as a metabolite produced a significant amount of DNA single strand breaks in V 79 cells. When diphenylhydroxylamine was incubated with microsomes electron spin resonance spectrum was observed which indicated the formation of the diphenylnitroxide radical. This radical seems to be mediated by auto-oxidation rather than by enzymatic catalysis. Whether diphenylhydroxylamine might be responsible for the observed genetoxic effects of nitrosodiphenylamine assumed to be produced via active oxygen species is discussed.

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Studies on the variations of biologically important smoke constituents of popular cigarettes in several European countries and in the United States include investigations on the types and levels of volatile (VNA) and tobacco-specific nitrosamines (TSNA). GLC-TEA and HPLC-TEA methods are used to determine the VNA and TSNA in mainstream and sidestream smoke of cigarettes. This report presents data on the smoke of some West German cigarettes which demonstrate that the VNA levels are about the same as those in the smoke of U.S. cigarettes; but that they are lower than those in the smoke of French cigarettes, made of dark tobacco types. The tobacco-specific nonvolatile N-nitrosamines determined in the mainstream smoke of commercial U.S. blended cigarettes (N-nitrosoanatabine, N-nitrosonornicotine and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone together) ranged from 680 to 830 ng per cigarette, while those for commercial West German products ranged from 340 to 780 ng per cigarette in nonfilter brands and from 180 to 450 ng in filter-tipped cigarettes. The analyzed French products contained 1010 to 1380 ng of these compounds in the smoke of each cigarette.