One of the big questions in genetic toxicology is what follow-up tests should be done for those awkward chemicals that give evidence of activity in in vitro assays but are inactive in the in vivo micronucleus test for chromosome damage (traditionally the most widely used in vivo genotoxicity test). As not all rodent carcinogens induce micronuclei, it has been common practice to conduct a second in vivo assay, often for unscheduled DNA synthesis (or UDS, an indirect measure of DNA damage), but concerns have been expressed that this may not be the most appropriate follow-up test system. Researchers have now analysed the results published for the UDS test and two other in vivo assays, the TG (transgenic mutation) assay and the comet assay (for DNA strand breakage), in relation to 67 carcinogens that were negative or equivocal in the micronucleus test. Overall, accolades were awarded to the comet and TG assays, with the scientists concluding that these two test systems “should be preferred to the rat liver UDS assay for regulatory testing” (Kirkland D. and Speit G., Mutation Research 2008, 654, 114). {178218}

The above item was taken from the September 2008 issue of Toxicology and Regulatory News which is sent automatically to members of bibra (click here for more details).

News Home Guest Write For Us? Contact Us