methylnitronitrosoguanidine and 2-aminofluorene

The aromatic amine 2-aminofluorene (2-AF) was activated by the intact Chlamydomonas reinhardtii cells to a mutagen that exhibited toxic and mutagenic effects comparable to those of the direct-acting mutagen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). There were different responses of the wildtype and repair-deficient strains to the toxic and mutagenic effect of 2-AF. The recombination repair plays a major role in repair of damages induced in the C. reinhardtii DNA by the aromatic amine promutagen 2-AF and the direct-acting mutagen MNNG. The 2-AF activation has also been analyzed by algal cells/microbe coincubation assay. This new assay is used in addition to animal microsome-metabolizing system (S9 fraction) and plant cell/microbe coincubation assay. This additional system is suitable for detection of environmental promutagens and their conversion to mutagens, mainly in aquatic environments.

Topics: Animals; Biotransformation; Chlamydomonas reinhardtii; Coculture Techniques; Fluorenes; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutagens; Prodrugs; Salmonella typhimurium

Taurine (2-aminoethanesulfonic acid) was evaluated as an antimutagen in the Ames Salmonella tester strain assay. Taurine inhibited mutagenesis by doxorubicin (-74%), bleomycin (-55%), mitomycin C (-56%), and 2-aminofluorene (-52%), but not danthrone or benzo(a)pyrene, in strain TA102. In strain TA98, doxorubicin mutagenicity, but not that of 2-aminofluorene or benzo(a)pyrene, was inhibited by taurine. N-Methyl-N'-nitro-N-nitrosoguanidine (-73%), but not dexon, mutagenicity was inhibited by taurine in strain TA100. Taurine inhibited those mutagens against which it was effective in a dose-related fashion. Taurine was more effective in inhibiting doxorubicin mutagenicity in strain TA102 than its analogues hypotaurine, beta-alanine, and guanidinoethanesulfonic acid or alanine or glycine. The observed inhibition may indicate a role for taurine in modulating the activity of oxidant species.

Topics: Amino Acids; Benzenesulfonates; Benzo(a)pyrene; Bleomycin; Dose-Response Relationship, Drug; Doxorubicin; Fluorenes; Methylnitronitrosoguanidine; Mitomycin; Mitomycins; Mutagenicity Tests; Mutagens; Salmonella typhimurium; Taurine

Since its development by Dr. Bruce Ames and his colleagues more than a decade ago, the Salmonella/mammalian microsome mutagenicity assay has become a widely accepted tool to assist in the identification of chemicals with mutagenic and carcinogenic potential. Several automated approaches to Salmonella testing have been proposed in recent years but have failed to gain acceptance in the scientific community due to poor performance or lack of demonstrated usefulness. In this paper we report on an automated system that successfully generates dose-response data and, moreover, reduces the labor, materials, and sample mass required to obtain such information. In the standard plate-incorporation assay, dose-response relationships are defined by testing discrete doses of the test agent on a series of agar plates. In contrast, the spiral Salmonella assay generates dose-response data from a continuous concentration gradient on a single agar plate. Upon analysis, each spiral plate yields a dose-response curve consisting of 13 data points that span a concentration range of about 15:1, which is equivalent to 5 two-fold serial dilutions. The performance of the spiral Salmonella assay was compared to that of the conventional plate-incorporation assay using 13 mutagens and 7 nonmutagens selected from a variety of chemical classes. Concordant qualitative responses were obtained for all compounds tested, and comparable dose-response relationships were generated by all mutagens with the exception of sodium azide and cyclophosphamide, which are highly water-soluble and, thus, are unable to maintain a well-defined concentration gradient on a spiral plate due to rapid diffusion. In general, toxicity was expressed at a lower dose in the spiral assay, and the mutagenic potencies (slopes of the dose-response curves) were greater in the spiral assay relative to the plate-incorporation assay. These differences will be discussed, as will the applicability of the spiral plating technique to routine screening and its relevancy to future mutagenesis testing.

Topics: 4-Nitroquinoline-1-oxide; Anthracenes; Biotransformation; Fluorenes; Image Processing, Computer-Assisted; In Vitro Techniques; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutation; Salmonella typhimurium; Time Factors

Aminofluorene (AF) and dimethylnitrosamine (DMN) were examined for their ability to induce multiple genetic endpoints after rat and hamster hepatocyte metabolic activation. The endpoints measured included mutations at the Na+/K+-ATPase (ouabain resistance) and hypoxanthine-guanine-phosphoribosyltransferase (6-thioguanine resistance) loci, and sister-chromatid exchanges (SCEs) in Chinese hamster V79 cells, and mutation of Salmonella typhimurium strains TA98 and TA100. AF, with rat and hamster hepatocyte activation, induced only low levels of mutations at either loci in V79 cells but did induce SCEs. Mutation of Salmonella by AF after hepatocyte activation also occurred and was a sensitive endpoint for detecting this aromatic amine. DMN induced high levels of mutations at both loci in V79 cells in addition to SCEs in the presence of hepatocytes from both species. DMN was also mutagenic to Salmonella, but only with hamster hepatocytes. Salmonella did not respond as strongly to DMN as the V70 cells. Hamster hepatocytes were more active than rat hepatocytes in activating both carcinogens. The results indicate the variable sensitivity of the genetic endpoints and species differences in activation for two potent chemical carcinogens.

Topics: Animals; Biotransformation; Cell Line; Cricetinae; Cricetulus; Dimethylnitrosamine; Fluorenes; Hypoxanthine Phosphoribosyltransferase; In Vitro Techniques; Kidney; Liver; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutagens; Mutation; Rats; Salmonella typhimurium; Sister Chromatid Exchange; Sodium-Potassium-Exchanging ATPase