Relationships between metabolic deactivation of ICR compounds and their differential mutagenicity in bacteria and cultured mammalian cells.

Preparations of Chinese hamster ovary (CHO) cells decreased the genotoxicity of 3 ICR compounds (ICR 191, ICR 191-OH and ICR 170-OH), while they did not affect the genotoxicity of ICR 170 in the Salmonella reversion test nor in a DNA-repair test in E. coli. These data may contribute towards the explanation of the lack of activity of the two hydroxylated compounds in the CHO/HGPRT forward mutation system, as well as the different rank of mutagenicity of the two chloroethyl compounds in bacteria (ICR 191 greater than ICR 170), compared to cultured mammalian cells and in general to eukaryotic cells (ICR 170 greater than ICR 191).