The in vivo induction of sister chromatid exchanges in the bone marrow of the Chinese hamster. II.N-nitrosodiethylamine (DEN) and n-isopropyl-alpha-(2-methyl-hydrazino)-p-toluamide (Natulan), two carcinogenic compounds with specific mutagenicity problems.

N-Nitrosodiethylamine (DEN) and N-isopropyl-alpha-(2-methylhyadrazino)-p-toluamide (Natulan) were examined with the in vivo SCE method of Vogel and Bauknecht. Only Natulan showed a positive effect with a significant increase of induced SCE between 10 and 25 mg/kg b.w. The six-point curve of the dose effect was of the plateau type. With DEN only a slight increase with high doses could be obtained, which was not significant when 50 or 100 cells were counted. Compared with the results of other tests published, Natulan gives positive results preferentially with in vivo mammalian tests but not with microorganisms. On the other hand, DEN is inactive in vivo on the chromosomal level, but preferentially induces point mutations at the molecular level in microorganisms and Drosophila. It is recommended to include in a battery of true mutagenicity tests also cytogenetic tests (in vivo SCE test and micronucleus test).