ABSTRACT
The ability of a TA7000 series of Salmonella his- mutant tester strains to detect mutagens as classified by the traditional tester strains (TA100, TA98, TA1535, TA1537, TA97, TA102 and TA104) was evaluated using 30 coded chemicals, 5 of which were duplicates with different code numbers. The TA7000 series of tester strains were TA7001, TA7002, TA7003, TA7004, TA7005 and TA7006, each of which reverts by a specific base substitution. In addition, each chemical was tested in a mixture of the base-specific strains (the Mix), plus the traditional strains, TA98 and TA1537. A liquid version of the Salmonella mutagenicity assay was performed in microtiter plates to allow partial automation for increased throughput. The results were compared to those in the National Toxicology Program (NTP) database, which were obtained from the traditional strains in the preincubation assay. In the two strains common to both protocols, TA98 and TA1537, the agreement was 80% and 85%, respectively. When compared to the NTP results for TA100, the Mix gave a 72% concordance, while the addition of the frameshift tester strain, TA98, increased the agreement to 76%. The overall agreement on positive or negative classifications of mutagenicity was 88% for the 25 chemicals tested. There were three notable exceptions to the overall agreement. Benzaldehyde was detected as a mutagen in TA7005 in contrast to its classification as a non-mutagen in the NTP database. This does not necessarily contradict the NTP results because the base-specific strains may respond to different mutagens. Two weak mutagens in the NTP database, 1-chloro-2-propanol and isobutyl nitrite, were not detected as mutagens in the base-specific new strains in the liquid protocol. While there are a number of major differences in the two assays, it was concluded that the results from each procedure are comparable.
Subject(s)
Mutagenicity Tests , Salmonella typhimurium/drug effects , Salmonella typhimurium/genetics , Reproducibility of ResultsABSTRACT
Evidence is provided that mutagenicity in Salmonella by a chromium(VI) salt and a chromium(III) compound has a differential dependence on the presence of oxygen. The mutagenic chromium(III) compound, cis-dichlorobis(2,2'-bipyridyl)chromium(III), reverted Salmonella strains, TA102 and TA2638, only under aerobic conditions. Potassium dichromate (chromium VI) required the presence of oxygen to revert the Salmonella strain TA102 but induced a moderate reversion frequency in TA2638 under anaerobic conditions. The data also support a role for oxygen radicals in chromium-mediated mutagenesis and suggests at least two pathways by which chromium compounds can induce mutations.