Mutagenicity and Cytotoxicity of Nineteen Heterocyclic Mustards (ICR Compounds) in Cultured Mammalian Cells¹

The mutagenicity and cytotoxicity of 19 ICR compounds, including 6 reported previously, have been determined in the Chinese hamster ovary/hypoxanthine-guanine phosphoribosyltransferase system. As with other physical and chemical agents, ICR 170 and 191 exhibit a phenotypic expression time of 7 to 9 days, independent of concentrations tested. Thirteen of these compounds are mutagenic. At equimolar concentrations, the compounds with the tertiary amine-type side chain (ICR 217, 340, 355, 368, 170, and 292) are more mutagenic than the compounds with the secondary amine-type side chain (ICR 449, 371, 191, and 372). All secondary amine types show a “plateau” in their concentration-dependent mutagenesis curves at 3 to 4 µm. Shortening of the side chain by one carbon (ICR 171) results in a reduced mutagenicity. Substitution of a sulfur atom for a nitrogen in the side chain (ICR 342) increases both mutagenicity and cytotoxicity. The presence of two 2-chloroethyl groups on the side chain (ICR 220) also results in greatly increased cytotoxicity and mutagenicity. When the 2-chloroethyl group of ICR 340, 372, 292, 191, or 170 is replaced by a 2-hydroxyethyl group (ICR 340-OH, 372-OH, 292-OH, 191-OH, or 170-OH), a mutagenically inactive compound results which remains toxic. Replacement of the amine linkage with an ether linkage (ICR 283) also yields a mutagenically inactive compound.