COMPARISON OF LACI AND LACZ TRANSGENIC MOUSE MUTATION ASSAYS - AN EU-SPONSORED INTERLABORATORY STUDY

As part of an EU Environment Programme sponsored study, the performanc e of two transgenic mouse mutation assays has been evaluated in three laboratories using common liver samples. The systems studied were the lacI(-) (Big Blue(TM)) mutation assay, and the GalE(-) positive select ion modified lacZ(-) (Muta(TM)Mouse) assay. The liver samples compared were derived from mice treated with either saline or dimethylnitrosam ine (DMN; 14 day recovery). Each assay gave an increased mutation freq uency (MF) for the DMN-treated livers when compared to the saline cont rol MFs. Sources of variability in the assays are discussed, and it is concluded that whole liver should be homogenised before DNA extractio n, and that concurrent controls should be processed in parallel with t est samples.