Genetic and cytogenetic effects of 1,3-dimethyl-3-phenyl-1-nitrosourea in Salmonella typhimurium and Chinese hamster V79 cells.

1,3-Dimethyl-3-phenyl-1-nitrosourea (DMPNU) shows no spontaneous decomposition in aqueous buffered solution (pH 7.0) at 37 degrees C over a measuring period of 10 days, but it is directly genotoxic in all assays applied. This compound induces base substitutions in Salmonella typhimurium (especially in the plasmid harbouring strain TA 100), gene mutations at the HGPRT+ locus of Chinese hamster V79 cells, and is a very potent inducer of clastogenic damage and sister chromatid exchanges in V79 cells. Data on gene mutation induction by 1-methyl-1-nitrosourea are included for comparison. The findings on DMPNU are discussed in comparison with trialkylnitrosoureas. In contrast to these latter compounds, DMPNU is active without addition of S9 mix in vitro. It is assumed that its genotoxic activity is due to an intracellular catalytic degradation favoured by the electron-withdrawing effect of the phenyl group.