THE SOS CHROMOTEST - A REVIEW

The SOS chromotest is reviewed through over 100 publications correspon ding to the testing of 751 chemicals. 404 (54%) of these chemicals pre sent a genotoxic activity detectable in the SOS chromotest. Their SOS inducing potencies span more than 8 orders of magnitude. For 452 compo unds, the results obtained in the SOS chromotest could be compared to those obtained in the Ames test. It was found that 373 (82%) of these compounds give similar responses in both tests (236 positive and 137 n egative responses). Thus the discrepancies between both tests concern 79 compounds (18%). A case by case analysis shows that many of these c ompounds are at the same time very weak SOS inducers and very weak mut agens. Thus we think that, most of the time, the discrepancies between the two tests may be accounted for by differences in the interpretati on of the results rather than by the experimental results themselves. However, there are some compounds which are clearly SOS inducers but d evoid of mutagenic activity in the Ames test (such as quinoline-1-oxid e) and to a larger extent, clearly mutagenic compounds which do not in duce the SOS response in the SOS chromotest (such as benzidine, cyclop hosphamide, acridines, ethidium bromide). We also analyzed the correla tion between SOS induction, mutagenesis and carcinogenesis according t o the classification of Lewis. For 65 confirmed carcinogens (class 1), the sensitivity, i.e., the capacity to identify carcinogens, was 62% with the SOS chromotest and 77% with the Ames test. For 44 suspected c arcinogens (class 2), the sensitivity was 66% with the SOS chromotest and 68% with the Ames test. Thus, we confirmed previous observations m ade on 83 compounds that there is a close correlation between the resu lts given by both bacterial tests. The capacity of the Ames test to id entify carcinogens is higher than that of the SOS chromotest. However, because the number of false.positive compounds was lower in the SOS c hromotest, the specificity, i.e., the capacity to discriminate between carcinogens and non-carcinogens of the SOS chromotest, appeared highe r than that of the Ames test. Thus, the results of the SOS chromotest and of the Ames test can complement each other. The SOS chromotest is one of the most rapid and simple short-term test for genotoxins and is easily adaptable to various conditions, so that it could be used as a n early - perhaps the earliest - test in a battery.