Frameshift mutagenesis by chloroquine in Escherichia coli and Salmonella typhimurium

Chloroquine can be detected as a direct-acting mutagen in plate-incorporation assays using the excision-deficient Salmonella typhimurium strain TA97, but very much more effectively using the repair-proficient Escherichia coli strain DG1669 which carries the lacZ19124 marker. When tested at concentrations of 200-1000 micrograms/plate with strain DG1669, the mutagenicity of chloroquine is enhanced by the addition of Aroclor-induced rat-liver S9. Further experiments indicated that chloroquine-induced reversion frequencies were essentially identical in wild-type, recA, umuC and uvrC derivatives of DG1669, as well as in strains carrying the mutation enhancing plasmid pKM101, over a wide range of doses (0-1200 micrograms/plate). These results suggest that neither excision repair nor SOS-type repair are important in chloroquine-induced frameshift mutagenesis.