Use of transgenic mouse lacI/Z mutation assays in genetic toxicology.

The Big Blue (lacI) and the Muta Mouse (lacZ/GalE) assays offer a practical means to generate mutation data from a wide range of tissues of treated animals. Our experience with these assays has so far been encouraging, but several fundamental questions require addressing. Chief among these is whether these assays are to be regarded as replacements for standard rodent genotoxicity assays, or if they are to be regarded as assays for the prediction of potential carcinogenic organotropy using a multiple-dose protocol. The interplay between the independent chemical properties of mitogenesis and DNA adduction require also to be studied. The value and sensitivity of these assays can only be assessed when these questions have been internationally addressed and concluded.