Mutagenicity of carcinogenic azo dyes and their derivatives

Human urine mutagenicity study comparing cigarettes which burn or only heat tobacco

Cigarette smokers have been reported to void urine which is more mutagenic, as measured in the Ames bacterial mutation assay, than urine voided by non-smokers. Condensate from the mainstream smoke of a cigarette which heats, but does not burn tobacco (test cigarette) showed no evidence of mutagenicity in a battery of in vitro genotoxicity assays under conditions in which condensate from the mainstream smoke of cigarettes that burn tobacco was mutagenic. The objective of this study was to determine whether the absence of mutagenic activity observed in the in vitro assays would be reflected in the urine of smokers of the test cigarette. 72 subjects (31 smokers and 41 non-smokers) were enrolled in a 6-week study, with the smokers randomly divided into 2 groups. The study was designed as a double crossover, with each smoker smoking both test (tobacco-heating) and reference (tobacco-burning) cigarettes. This design allowed each smoker to serve as his or her own control while at the same time allowing comparisons between groups of non-smokers and smokers of both test and reference cigarettes. 24-h urine samples were collected twice a week and concentrated using XAD-2 resin. Urine concentrates were tested in Ames bacterial strains TA98 and TA100, with and without metabolic activation and with and without beta-glucuronidase/aryl sulfatase. Individuals who smoked the test cigarette voided urine which was significantly less mutagenic than that voided when they smoked reference cigarettes. The mutagenicity of urine from smokers who smoked the test cigarette and non-smokers did not differ under any of the assay conditions used in this study.

A genotoxic assessment of environmental tobacco smoke using bacterial bioassays

Recently, the National Research Council in the U.S.A. stated that laboratory studies of environmental tobacco smoke (ETS) should be important in identifying ETS carcinogens, their concentrations in typical daily environments, and in understanding how these compounds contribute to ETS dose-response relationships. This paper demonstrates that integrated chemical and bacterial mutagenicity information can be used to identify ETS genotoxicants, monitor human exposure, and make comparative assessments. Approximately 1/3 of the ETS constituents for which there is quantitative analytical chemistry information also have associated genotoxicity information. For example, 11 of the quantitated compounds are animal carcinogens. Work presented in this paper demonstrates that both the nonparticle-bound semivolatile and the particulate-bound organic material contain bacterial mutagens. These ETS organics give an equivalent of approximately 86,000 revertants per cigarette. In addition, this article summarized efforts to estimate ETS bacterial mutagenicity, to use bacterial tests for the monitoring of ETS-impacted indoor environments, and to use bacterial assays for the direct monitoring of human exposure.

Mutagenicity studies on fenitrothion in bacteria and mammalian cells

The mutagenicity of fenitrothion was determined in strains of Salmonella typhimurium and Escherichia coli. Fenitrothion was found to be non-mutagenic in Salmonella typhimurium strains of TA98, TA1535 and TA1537 and in Escherichia coli WP2uvrA both with and without S9 mix, while weak mutagenicity was observed only in Salmonella typhimurium TA100 and enhanced by the addition of S9 mix. The mutagenicity observed in the TA100 strain was not expressed in a nitroreductase-deficient strain, TA100 NR, and decreased in a transacetylase-deficient strain, TA100 1,8-DNP6. The mutagenicity of fenitrothion was also examined by a gene mutation assay using the gene for hypoxanthine-guanine phosphoribosyltransferase (hgprt) in V79 Chinese hamster lung cells. Fenitrothion did not induce any increment of 6-thioguanine-resistant mutant cells at doses ranging from 0.01 to 0.3 mM regardless of the presence or absence of S9 mix. These results suggest that reduction of fenitrothion by a bacterial nitroreductase of TA100 to an active form is essential for the expression of the mutagenicity of fenitrothion in TA100 and that a bacterial transacetylase of TA100 also has an important role in the process of mutagenic activation.

Cytotoxicity and effect on mutagenicity of buffers in a microsuspension assay

We have examined the effects of three buffers--Vogel-Bonner minimal E (VBM) and 0.15 and 0.015 M sodium phosphate, pH 7.4--and two concentrations of overnight cells (5x and 10x) on the mutagenicity of two pure compounds and two complex mixtures in strain TA98 using a modification of a microsuspension assay developed by Kado et al. (Mutation Research 121:25-32, 1983). The assay was performed by adding 50 microliters of cell concentrate of an overnight culture of TA98 resuspended in the appropriate buffer; 50 microliters of the same buffer or S9 mix; and 2 microliters of mutagen or dimethyl sulfoxide to a 1-dram vial or 13 x 150-mm test tube. The suspension was incubated for 90 min at 37 degrees C, top agar was added, and the contents poured onto a bottom agar of minimal medium. Cell concentration (5x vs. 10x) had little effect on the mutagenic potencies of the agents tested. The mutagenic potencies of the direct-acting agents (1-nitropyrene and diesel exhaust) were consistently lower with 0.15 M buffer compared to the mutagenic potencies of these agents with the other two buffers. The three buffers gave similar results for the indirect-acting agents (2-aminoanthracene and environmental tobacco smoke). The 0.15 M buffer was considerably cytotoxic in the absence of S9, which may explain why the direct-acting agents were less potent with this buffer compared to the other buffers. VBM was also somewhat cytotoxic, but this did not appear to affect the mutagenic potencies of the agents studied.(ABSTRACT TRUNCATED AT 250 WORDS)

N,N-diethylphenylacetamide, an insect repellent: absence of mutagenic response in the in vitro Ames test and in vivo mouse micronucleus test

N,N-diethylphenylacetamide (DEPA), a promising new insect repellent, was tested for mutagenicity in the in vitro Ames Salmonella/microsome mutagenicity test and the in vivo mouse micronucleus test. For the Ames test, DEPA was assayed both in the presence and absence of Aroclor 1254-induced rat-liver S-9 mix (5 and 20% S-9 fraction), using five tester strains of Salmonella typhimurium--TA97a, TA98, TA100, TA102 and TA104. For the micronucleus test, mice were exposed to DEPA through ip injection for 2 and 5 days in separate experiments, and bone marrow and peripheral blood were sampled 6 and 48 hr after the final injection, respectively. DEPA did not induce a mutagenic response in the Ames test, and mouse bone marrow and peripheral blood micronucleus tests. DEPA was not considered cytotoxic, as a depression of the percentage PCE was not observed at any dose in the range of 1 to 100 mg/kg body weight with either treatment protocol of the micronucleus test.

Mutagenicity and cytotoxicity of N-methyl-2-pyrrolidinone and 4-(methylamino)butanoic acid in the Salmonella/microsome assay

The industrial solvent N-methyl-2-pyrrolidinone (NMP) and its hydrolysis product, 4-(methylamino)butanoic acid (N-MeGABA), were examined for mutagenicity and cytotoxicity in the Ames Salmonella/microsome assay. In order to detect a broad range of possible mutagenic endpoints, the following strains were used in the assay: base-pair substitution strains TA100, TA102 and TA104; frameshift strains TA97 and TA98; and repair proficient strains TA2638, UTH8413 and UTH8414. In the standard plate incorporation assay, six log-linear doses of each compound were tested; doses ranged from 0.01 to 1000 mumol/plate for NMP, and 0.01 to 316 mumol/plate for N-MeGABA. Neither compound was detectably mutagenic when tested in the presence and absence of metabolic activation by Aroclor-induced rat liver S9. NMP did show significant responses with strains TA102 and TA104 that were less than two-fold over background, but no clear dose-response relationships were evident. A preincubation modification of the assay was also performed, using strains TA98 and TA104. Mutagenic activity was not observed for NMP, while N-MeGABA showed significant responses with TA104 but dose-related mutagenicity was not established. Preincubation testing revealed both NMP and N-MeGABA to be cytotoxic to the test population of Salmonella at the highest treatment doses.

Mutagenicity, comutagenicity, and antimutagenicity of erythrosine (FD and C red 3), a food dye, in the Ames/Salmonella assay

Erythrosine (diNa, tetraiodofluorescein) was nonmutagenic to the Ames/Salmonella typhimurium strains TA97a, TA98, TA100, TA102, and TA104, to a concentration of 2 mg/plate. No mutative intermediates were detected on metabolism by rat caecal cell-free extracts or rat liver S9 mixture; or on incubation with the comutagens, harman and norharman (+/- S9). Instead, an unexpected dose-dependent suppression in spontaneous reversion frequencies was observed (maximum approximately equal to 35% decrease). Erythrosine was antimutagenic to benzo[a]pyrene, but it did not decrease the mutagenicity of the other adduct-forming mutagen, 4-nitroquinoline N-oxide. The food dye was strongly antimutagenic to the bifunctional alkylating agent, mitomycin C, though it did not exhibit a similar effect on the mutagenicity of the corresponding monofunctional agent, methyl methanesulphonate. It partially depressed the mutagenic potentials of sodium azide. The antimutagenic effect of erythrosine on an intercalating agent, ethidium bromide, was discernible only at the highest dose (2 mg/plate). These results have been interpreted in terms of a genointeractive role of erythrosine. Erythrosine produced differential toxic effects in repair-deficient (TA97a, TA98, TA100) and repair-proficient (TA102, TA104) Salmonella tester strains; survival of the repair-deficient strains was found to be decreased. Photoinduced potentiation of erythrosine toxicity was observed, although light irradiation in the presence of erythrosine did not modify the reversion frequencies of the tester strains. The evidence strongly suggests that erythrosine, which exhibits nonmutagenicity in the Ames/Salmonella test, can interact with DNA repair enzymes and/or with DNA.

Testing for mutagens in an aluminium plant. The results of Salmonella typhimurium tests on urine from exposed workers

Urine concentrates from workers in a Söderberg potroom and an anode paste plant were tested for mutagenicity by the Salmonella reversion assay. The study is aimed at group exposure as an indicator of the effect of the work atmosphere. Urine from exposed smokers showed mutagenic activity, whereas urine from exposed non-smokers did not. The mutagenicity of exposed smokers' urine was not significantly different from the urine from non-exposed smokers. Significant mutagenicity of smokers' urine was evident only in the presence of a rat-liver metabolic system. Since an earlier expectorate analysis has shown that mutagens from the work atmosphere are deposited in the workers' respiration system and the urine analysis does not show any effect of occupational exposure, it is likely that the mutagens are eliminated from the body via other routes than renal excretion.

Mutagenicity of methyl isocyanate in the modified test conditions of Ames Salmonella/microsome liquid-preincubation procedure

Methyl isocyanate (MIC) was tested for mutagenicity using the Ames Salmonella/microsome liquid-preincubation procedure with slight modification of test conditions. In the modification the preincubation mixture was incubated at 10 degrees C for 60 min. MIC was assayed both in the presence and absence of Aroclor-1254-induced S9, using 5 tester strains of Salmonella typhimurium, TA97a, TA98, TA100, TA102 and TA104. MIC induced mutagenic response in two base-pair substitution strains, TA100 and TA104, in the presence and absence of S9. However, mutagenic response in the presence of S9 was low as compared to that in the absence of S9. In the comparative mutagenic activity at 3 different preincubation test conditions (37 degrees C for 20 min, 20 degrees C for 40 min and 10 degrees C for 60 min), optimum mutagenic response was observed at 10 degrees C for the 60-min test condition. However, no mutagenic response was observed at 37 degrees C for the 20-min test condition.

DNA repair test of disinfectants by liquid rec-assay

The DNA-damaging capacity and the mutagenicity of 6 disinfectants were studied by liquid rec-assay and Ames test. 5 disinfectants were found to be positive in DNA-damaging capacity while only one of them showed clear mutagenicity in the Ames test. Liquid rec-assay by direct incubation with S9 mix was the most sensitive method and gave the best correlation between the growth ratio (R 50) and the time lag, both of which compared Rec+ and Rec-. Liquid rec-assay may be useful for detecting the DNA-damaging capacity of chemicals with a strong killing effect.

Relationships between structure and mutagenic activity of environmental chemicals

This review analyzes relationships between chemical structure and biological activity for several series of compounds. Its focus is on mutagenicity and carcinogenicity and the predictability of these properties on the basis of the chemical structure. Examples are selected from monocyclic aromatic amines, benzidine derivatives, aminoazobenzene derivatives, nitrofurans, aflatoxins, and sterigmatocystins. Results from mutagenicity tests in Salmonella typhimurium are summarized, and their correlation with carcinogenicity is discussed. The review is concluded with generalizations on the usefulness of studies on relationships between chemical structure and mutagenic activity.

Guide for the Salmonella typhimurium/mammalian microsome tests for bacterial mutagenicity

Since its development by Dr. Bruce Ames and his coworkers, the Salmonella typhimurium/mammalian microsome mutagenicity assay has been used widely throughout the world. Many authors have suggested various modifications and made recommendations in regards to this assay. Although the recommendations of a panel of experts was published in 1979 by de Serres and Shelby, a committee of members of the Environmental Mutagen Society (EMS) initiated this effort in response to the encouragement by the American Society of Testing and Materials (Committee E47.09.01) and because of new developments within the field of microbial mutagenesis testing. Its purpose is to provide a guide for people who perform or evaluate microbial mutagenesis tests, but it is not intended for these recommendations to replace or diminish the usefulness of presently available protocols and procedures.

Mutagenicity tests of cashewnut shell liquid, rice-bran oil and other vegetable oils using the Salmonella typhimurium/microsome system

In view of the shortage of edible oils in India, nutritional and toxicological evaluations have been carried out on some unconventional oils to determine whether they might be safe for human consumption. As part of these evaluations, eight unconventional oils were tested by the Ames mutagenicity assay, using Salmonella typhimurium strains TA98 and TA100 with and without metabolic activation with S-9 mix prepared from the livers of rats pretreated with sodium phenobarbitone or Aroclor 1254. Of the oils tested, metsa oil (Hibiscus sabdariffa) and cashewnut shell liquid were mutagenic with and without metabolic activation with S-9 of either source. No mutagenic activity (with or without S-9 of either source) was observed with any of the other oils tested (rice-bran oil, Cleome viscosa oil, mango-kernel oil, mahua oil, kapok oil and neem oil).

Mutagenicity of selected aniline derivatives to Salmonella following plant activation and mammalian hepatic activation

We compared several phenylenediamines (4-nitro-o-phenylenediamine, NOP; 2-nitro-p-phenylenediamine, NPD; o-phenylenediamine, OPD; p-phenylenediamine, PPD; m-phenylenediamine, MPD) and aniline (ANL) for mutagenicity to Salmonella directly and following activation by plant and mammalian hepatic S9 using plate incorporation and preincubation protocols. In addition, we assayed each chemical for activation by intact plant cells using the plant cell/microbe coincubation protocol. At the concentrations tested, NOP, NPD, OPD, MPD and ANL were active in one or more assays. NPD, OPD and MPD were activated by mammalian hepatic S9 in one or more assay and each was activated by plant S9 or intact plant cells. ANL was mutagenic only in the presence of plant S9. PPD was not active under any of the test conditions.

Mutagenicity of some substituted 1-phenyl-3,3-dimethyltriazenes. I. The salmonella/mammalian microsome assay and repair test

The mutagenic activity and related biological properties of Br-, Cl-, NO2- and CH3-derivatives of 1-(phenyl)-3,3-dimethyltriazene were investigated in Salmonella/microsome assays with standard and preincubation metabolic activation and in the repair test using Salmonella and E. coli B/r. In the repair test, the CH3-derivative was slightly positive in the E. coli recA and uvrA repair system, the NO2-derivative had a killing effect on Salmonella typhimurium uvrB-deficient strains. In Salmonella mutagenicity assays, all tested triazene derivatives reverted frameshift tester strains, especially TA1537. The highest number of frameshift mutations was induced by the CH3-derivative in the presence of a standard metabolic activation system; direct mutagenicity of this derivative was weak, reaching about the same level of activity as seen after preincubation. The only test compound that induced mutations of the base-substitution type was the NO2-derivative; this derivative showed the highest mutagenicity when activated by preincubation.

Biological and chemical studies on overheated brewed coffee

Vapour formed from overheated decaffeinated coffee was condensed and tested for mutagenicity using the Ames assay in Salmonella typhimurium strains TA98 and TA100. Vapour produced at 73 and 100 degrees C exhibited no mutagenicity. The basic fraction of vapour produced at 350 degrees C showed weak mutagenicity towards strains TA98 with metabolic activation. The chemical analysis of this fraction identified pyridines and pyrazines as the major constituents. None of the compounds identified in this fraction has been reported as mutagenic when tested in the Ames assay.

Mutagenic and leukemogenic activity of haloperidol: a negative study

The mutagenic and leukemogenic potential of haloperidol, a neuroleptic of the butyrophenone class, has been studied in an in vitro Ames Salmonella/microsome test and in an 18-month carcinogenicity study in mice. Three variants of the Salmonella mutation assay were included: the spot test, the standard plate incorporation test and the preincubation test. There was no evidence that haloperidol had any mutagenic activity in any of the Salmonella mutation tests with any of the Salmonella typhimurium tester strains in the presence or absence of Aroclor 1254-induced rat- or mouse-liver S9-mix. In the 18-month study, haloperidol was injected intraperitoneally as a solution (HaldolR) at a dosage of 5 mg/kg daily for 5, 10 and 20 consecutive days in 5-week-old mice. Leucocyte counts at several time points and histopathological tumor evaluation 18 months later did not reveal any leukemogenic or other carcinogenic effect. On the basis of these data, it may be concluded that haloperidol is not mutagenic in Salmonella nor leukemogenic in mice.

Salmonella/microsome mutagenicity tests of heat-processed milk samples

Samples of whole milk were heat treated by commercial heat-sterilization, by commercial heat-pasteurization or by a laboratory heat-pasteurization (65 degrees C for 30 min). Each sample was tested for mutagenicity in Salmonella typhimurium strains TA98 and TA100 with and without S-9 mix. Dichloromethane extracts of milk heated at 100, 135 and 150 degrees C for 5 hr were also tested for mutagenicity using the same assay. None of these samples exhibited mutagenicity in the Ames assay used.

The Salmonella typhimurium/mammalian microsomal assay. A report of the U.S. Environmental Protection Agency Gene-Tox Program

The Salmonella assay has been in use for almost 15 years and can be defined as a routine test for mutagenicity and for predicting potential carcinogenicity. It detects the majority of animal carcinogens and consequently plays an important role in safety assessment. The test is also routinely used as the frontline screen for environmental samples (complex mixtures) isolated from air, water and food. This role will continue to remain an area of growth as or because sample volumes associated with these testing areas are generally very limited and more extensive testing is generally impossible. While this test, like all others, has some limitations, it is recommended that it be regularly included in all genetic testing batteries.

Mutagenicity of chloroolefins in the Salmonella/mammalian microsome test. III. Metabolic activation of the allylic chloropropenes allyl chloride, 1,3-dichloropropene, 2,3-dichloro-1-propene, 1,2,3-trichloropropene, 1,1,2,3-tetrachloro-2-propene and hexachloropropene by S9 mix via two different metabolic pathways

In the presence of S9 mix all allylic chloropropenes tested exert considerable indirect mutagenic activity which is most pronounced for 1,2,3-trichloropropene. Lower as well as higher chlorinated derivatives are clearly less mutagenic. Longer than standard incubation time (120 min instead of 20 min) at 37 degrees C always leads to an increase in mutagenic activity. An increase in concentration of rat-liver homogenate fraction (S9) in the metabolising system (S9 mix) enhances mutagenicity only for 1,3-dichloropropene, 2,3-dichloro-1-propene and for the cis isomer of 1,1,2,3-tetrachloro-2-propene. According to the effects of the enzyme inhibitors SKF525 1,1,1-trichloropropene-2,3-oxide and cyanamide the allylic chloropropenes fall into 3 groups distinguished by their mode of metabolic activation by S9 mix: (a) allyl chloride and 1,3-dichloropropene are hydrolysed to the corresponding allylic alcohols which can be oxidised to the respective acroleins (hydrolytic-oxidative pathway); (b) 2,3-dichloro-1-propene, 1,1,2,3-tetrachloro-2-propene and hexachloropropene are epoxidised in the C=C double bond, giving rise to reactive epoxides (epoxidative pathway); (c) only 1,2,3-trichloropropene is obviously activated by both these alternative metabolic pathways. Structural parameters like chloro-substitution of the central C atom of the C=C-C sequence and substituent-induced polarisation of the C=C double bond as well as cis/trans isomerism might be responsible for different substrate properties for the enzymes involved in allylic chloropropene metabolism, thus determining different degrees of activation by either one or both pathways.

Mutagenicity of chloroolefins in the Salmonella/mammalian microsome test--II. Structural requirements for the metabolic activation of non-allylic chloropropenes and methylated derivatives via epoxide formation

Non-allylic chloropropenes and their methyl-homologues, being chloro-substituted exclusively in vinylic position, are mutagenic in the presence of metabolizing rat liver homogenate fraction (S9 mix). This can be interpreted as the result of polarizing inductive (I-) and mesomeric (M-) effects exerted by Cl- as well as by CH3-substituents on the olefinic double bond. The extent of their mutagenic activity increases with longer preincubation time and/or a higher concentration of rat liver homogenate fraction (S9) in the S9 mix. The only exception from this rule of a qualitative correlation of C = C-bond polarization due to asymmetric substitution and mutagenic activity is 1-chloro-2-methyl-1-propene which is non-mutagenic. In this case effects of a steric hindrance of two voluminous CH3-substituents attached to one C-atom of the C = C-bond might inhibit enzymatic attack of the double bond by microsomal oxygenase. Mutagenic activity is invariably decreased in the presence of SKF525, inhibitor of microsomal oxygenase, and increased when 1,1,1-trichloropropene-2,3-oxide (TCPO), inhibitor of epoxide hydrolase, is added to the test system. This is a strong argument for metabolic activation of these substances occurring via epoxide formation.

Comparative mutagenicity studies of azo dyes and their reduction products in Salmonella typhimurium

The arabinose-resistant and Ames assay systems of Salmonella typhimurium were used to evaluate the mutagenic potential of azo dyes and their aromatic amine reduction products. Azo dyes, namely direct black 38, direct blue 15, and direct red 2, were mutagenic in the arabinose-resistant and Ames assays with both hamster and rat liver S9 activation. Both assays gave relatively higher mutagenic responses with hamster S9. Reduction products of these dyes, namely benzidine, o-dianisidine, and o-tolidine, were mutagenic in the Ames assay. Benzidine was weakly mutagenic and o-dianisidine and o-tolidine were nonmutagenic in the arabinose-resistant assay. These results indicate that both arabinose-resistant tester SV50 and Ames tester TA98 were sensitive in detecting mutagenicity of azo dyes. The use of the standard plate protocol with Ames tester TA98 is more efficient than the modified azo dye protocol in detecting mutagenicity of aromatic amine reduction products. Additional modifications in either the standard plate or modified azo dye protocols may improve detection of mutagenicity of these compounds in the arabinose-resistant assay system.

3-Methoxy-4-aminoazobenzene, a unique carcinogenic aromatic amine as a substrate for cytochrome-P-450-mediated mutagenesis

Rat liver microsomal enzyme(s) that catalyze mutagenic activation of a carcinogenic aminoazo dye, 3-methoxy-4-aminoazobenzene (3-MeO-AAB), was studied by virtue of the Salmonella typhimurium TA98 assay using o-aminoazotoluene (OAT) as the control. Male Wistar rats were pretreated with phenobarbital (PB), 3-methylcholanthrene (MC) or polychlorinated biphenyl (PCB), and the liver microsomal activities for mutagenic activation of 3-MeO-AAB and OAT were examined. In agreement with the reported results on several carcinogenic aromatic amines, MC pretreatment resulted in greater activation of microsomal activity in the OAT mutagenesis (about a 4-fold increase as compared to the untreated control) than did PB (1.5-fold increase). By contrast, the mutagenic activation of 3-MeO-AAB is found to be more efficiently catalyzed by those enzyme(s) that are induced by PB pretreatment (4-fold increase) than by those that are induced by MC (1.8-fold increase). The induced enzymes that principally mediate the mutagenic activation of these azo dyes are indicated to be cytochrome P-450s, because the mutagenic activation was strongly inhibited by addition of cytochrome P-450 inhibitors such as 2-diethylaminoethyl-2,2-diphenylvalerate (SKF 525A) and 7,8-benzoflavone. These data suggest that 3-MeO-AAB is a unique carcinogenic aromatic amine as a substrate for mutagenic activation via catalysis of those cytochrome P-450s that are induced by PB pretreatment.

The effect of paraquat on the mutagenicity of benzo(a)pyrene

Elevated activities of superoxide dismutase (SOD) were detected in histidine-requiring strains of Salmonella typhimurium after the bacteria were preincubated for 1 h at 37 degrees C with S-9 mix and paraquat (methylviologen, PQ2+) at 10(-4) M. A fivefold increase in SOD level was found for strains TA 98 and TA 100. These elevated levels of SOD activity were correlated with a significant reduction of the mutagenicity of metabolically activated benzo(a)pyrene (B(a)P) in these tester bacteria when evaluated in a preincubation assay system. A 69.0-92.5% and 23.5-66.9% reduction was noticed when 0.5-4.0 micrograms per plate of B(a)P was used in TA 98 and TA 100, respectively. However, exogenous superoxide dismutase at 10-100 micrograms ml-1 added to top agar had no significant effect on the number of revertants produced by activated B(a)P. These data indicate a major role of intracellular superoxide anion in promoting mutagenicity of B(a)P.

Condensed tannins induce micronuclei in cultured V79 Chinese hamster cells

The tannins, delphinidin and procyanidin were isolated from flowers of white clover (Trifolium repens) and the leaves of Arnot Bristly Locust (Robina fertilis) respectively, and tested for mutagenic properties in a range of systems. There was no evidence for either compound causing significant levels of frameshift or base-pair mutagenesis in bacterial mutagenicity assays, although both were weakly positive in a bacterial DNA-repair test. Both compounds very slightly increased the frequency of petite mutagenesis in Saccharomyces cerevisiae strain D5. In V79 Chinese hamster cells, both were efficient inducers of micronuclei. In each of these test systems, increasing the potential of the compound for metabolic activation by addition of 'S9' mix had little effect on toxicity or mutagenicity of either tannin. It would seem that potential chromosome-breaking activity of condensed tannins could represent a carcinogenic hazard for animals grazing on pastures of white clover in flower. It may also have wider implications for human carcinogenesis by some, if not all, condensed tannins.

Mutagenic activity of acrinol in Salmonella typhimurium

Acrinol, which is used as a disinfectant and an abortifacient in several countries, was tested for mutagenicity by the Ames test system. After incubation with a rat-liver S9 microsomal preparation, acrinol showed potent mutagenicity for Salmonella typhimurium strains TA98 and TA100, although it had no direct mutagenicity for the microorganisms.

Mutagenicity of chloro-olefins in the Salmonella/mammalian microsome test. I. Allyl chloride mutagenicity re-examined

Contrary to findings published up to now, allyl chloride, a well known directly acting mutagen for Salmonella typhimurium, is efficiently activated by rat-liver homogenate (S9 mix) under non-standard mutagenicity testing conditions. Its indirect, S9-mediated mutagenic activity is greatly enhanced when longer than standard preincubation times are applied. The indirect mutagenicity of allyl chloride, thus revealed, greatly exceeds its direct mutagenic activity. Obviously, standard mutagenicity testing conditions cannot be regarded as reliable tools for the evaluation of the full genotoxic potential of allyl chloride and, possibly, of other related compounds.

Evaluation of 1,3-pentadiene for mutagenicity by the Salmonella/mammalian microsome assay

1,3-Pentadiene, a food contaminant produced by some molds when they metabolize sorbic acid, was tested for mutagenicity, using variations of the Salmonella/mammalian microsome assay. The chemical was incorporated into the test system (with and without S9 mix) by 3 methods: (a) the standard plate incorporation assay, (b) a liquid preincubation procedure and (c) exposure of test bacteria in the soft agar overlay to gaseous 1,3-pentadiene. The chemical was extremely toxic to the test bacteria with amounts as low as 2.0 microgram/plate causing cell death. However, none of the nonlethal concentrations tested by any of the methods was mutagenic to Salmonella typhimurium strains TA97, TA98, TA100, TA1535, TA1537 or TA1538.

The SOS Chromotest, a colorimetric bacterial assay for genotoxins: validation study with 83 compounds

The SOS Chromotest is a simple bacterial colorimetric assay for genotoxicity. It is based on the measure of the induction of sfiA, a gene controlled by the general repressor of the SOS system in E. coli. Expression of sfiA is monitored by means of a gene fusion with lacZ, the structural gene for beta-galactosidase. We have examined 83 compounds of various chemical classes with the SOS Chromotest using a standard procedure. Comparison of the results with those obtained in the Mutatest (the Ames test) showed that most (90%) of the mutagenic compounds were also SOS inducers. For these compounds a quantitative correlation was observed between the mutagenic potency and the SOS-inducing potency (SOSIP). The case of the 10% remaining compounds giving conflicting results in the two tests is discussed. Sensitivity, specificity and accuracy for carcinogenicity prediction have been evaluated for the SOS Chromotest and the Mutatest using 73 chemicals for which carcinogenicity data were available. In spite of some differences, similar results were obtained in the two tests. The present data indicate that the SOS Chromotest has many practical advantages and may be used as a primary screening tool or as part of a battery of short-term tests for carcinogens.

Mutagenic characteristics of formaldehyde on bacterial systems

The mutagenic characteristics of formaldehyde on bacteria were examined. All the tester strains of Escherichia coli deficient in DNA-repair enzymes tested in the present study were significantly more sensitive to the killing effect of formaldehyde than the corresponding wild-type strain. Among the E. coli B strains, H/r30R (wild-type) and Hs30R (uvrA) were mutable, whereas NG30 (recA) and O16 (polA) were not. There is no appreciable difference in mutation frequency of E. coli B between the wild-type and the uvrA strains in a dose range below 4 mM. However, the mutation frequency of the wild-type strain started to decrease in a higher concentration range, whereas that of the uvrA strain continued to increase linearly. This was confirmed with the E. coli B/r tester strains. The decrease in mutation frequency may be produced by prolongation of the lag period before entering the S-phase so as to give the cells a greater chance for DNA repair through the excision mechanism. In fact, it was evidenced that formaldehyde retarded to a remarkable extent the initiation of DNA synthesis of the cells at the higher dose range used for mutation assay. Some discrepancies found between the results obtained in this study and those previously reported by Nishioka (1973) were pointed out.

Allyl isothiocyanate is mutagenic in Salmonella typhimurium

Allyl isothiocyanate, a naturally occurring compound, component of oil of mustard and human food plants such as cabbage, cauliflower and horseradish, has up to now been regarded as nonmutagenic in bacterial mutagenicity testing systems. Recently, however, it was found to cause transitional-cell papillomas in the urinary bladder of male F344 rats. Contrary to earlier reports, in this study allyl isothiocyanate showed clear mutagenicity for Salmonella typhimurium TA100 in the preincubation assay after longer, non-standard preincubation times (greater than 20 min). The mutagenicity is expressed only in the presence of a rat-liver homogenate metabolising system, i.e. it is indirect. However, high concentrations of rat-liver homogenate suppress the mutagenicity of allyl isothiocyanate. SKF525, inhibitor of microsomal oxygenase, reduces the mutagenic potential which on the other hand is increased in the presence of 1,1,1-trichloropropene-2-oxide, inhibitor of epoxide hydrolase. This indicates the occurrence of an epoxide intermediate in allyl isothiocyanate metabolism. Another metabolic pathway, namely hydrolysis to allyl alcohol and oxidation to acrolein, a known mutagen, also seems possible as cyanamide, inhibitor of aldehyde dehydrogenase, can slightly increase the mutagenic potential. The reason(s) for allyl isothiocyanate's requirement for long preincubation times to express mutagenicity still requires elucidation, and the question arises: is allyl isothiocyanate a single, exceptional case or not?

Weak mutagenicity to Salmonella of the formaldehyde-releasing anti-tumour agent hexamethylmelamine

Hexamethylmelamine (HEMLA) is a metabolism-dependent formaldehyde-releasing agent related in structure to hexamethylphosphoramide (HMPA). Both compounds are known to be mutagenic to Drosophila. HMPA, in common with the other formaldehyde-releasing agents studied, is non-mutagenic to Salmonella. The present paper describes the mutagenicity of HEMLA to strain TA100 of Salmonella typhimurium. Activity is dependent upon both the use of a pre-incubation assay protocol and on high concentrations of Aroclor-induced rat liver in the S9 mix. HMPA was inactive under similar conditions of test.

Mutagenicity of 4,4'-methylene-bis-(2-chloroaniline) "MOCA" and its N-acetyl derivatives in S. typhimurium

4,4'-methylene-bis-(2-chloroaniline) ("MOCA") and two identified urinary N-acetyl and N,N'-diacetyl derivatives were tested in a Salmonella/mammalian microsome assay. No mutagenic activity was observed without rat liver S9 mix activation. In the presence of rat liver S9 mix, the chemicals were mutagens, but the mutagenicity of N-acetyl derivatives to strain TA100 was reduced when compared to that of "MOCA", and a greater amount of S9 was required to exhibit the mutagenicity of the N,N'-diacetyl-"MOCA". These data suggest that N-acetylation does not account for the mutagenic effectiveness of "MOCA".

Mutagenic and alkylating activities of organophosphate impurities of commercial malathion

The purpose of this study was to determine if 4 major organophosphate impurities of malathion were active as alkylators of nitrobenzylpyridine (NBP) or as mutagens in the Salmonella typhimurium bioassay. Malathion, isomalathion, O,O,O-trimethyl phosphorothioate, O,O,S-trimethyl phosphorothioate, and O,S,S-trimethyl phosphorodithioate produced alkylated NBP at varying rates. In order of increasing NBP reactivity, the compounds ranked: O,O,O-trimethyl phosphorothioate = O,O,S-trimethyl phosphorothioate less than O,S,S-trimethyl phosphorodithioate less than isomalathion = malathion. At 37 degrees C, the most reactive compounds produced an NBP alkylation rate equal to approximately 25% of the rate produced by methyl methanesulfonate, a potent Salmonella mutagen. However, none of the organophosphates were mutagenic in S. typhimurium TA97, TA98 and TA100 when tested by the standard plate-incorporation method or by the preincubation modification of the plate-incorporation method. The possible relationships between NBP reactivity and the biological activities of these organophosphates are discussed.

Assay of mutagens in aqueous fecal extracts with a modified ames Salmonella test

Mutagenicity with Salmonella strain TA 100 can be determined by an island test in which only an isolated portion of a pour plate is spotted with a sample. The magnitude of the ratio of the numbers of revertant colonies on the treated and untreated parts of the plate reflects the potency of the mutagen. Five of six chemicals tested yielded statistically significant and generally linear dose-response curves. Minimum detectable mutagenic doses for four compounds calculated from the dose-response curves showed that the island test generally required less material for detection of mutagenicity than the liquid pre-incubation procedure. The island method was primarily designed to test the mutagenicity of aqueous extracts of human stool samples. Dose-responses were obtained for six such samples, and in two samples the amount of material needed for a positive response was significantly less than that required in the liquid pre-incubation method.

NADPH-generating system: influence on microsomal mono-oxygenase stability during incubation for the liver-microsomal assay with rat and mouse S9 fractions

Activity levels of 7-ethoxycoumarin O-deethylase (ED), aminopyrine N-demethylase (APD), p-nitroanisole O-demethylase (p-NAD) and glucose-6-phosphate dehydrogenase (G-6-PDH) were determined in incubation mixtures for the liver-microsomal assay (LMA) at time 0 and after 1 and 2 h incubation under conditions for mutagenic assay. The experiments were performed with S9 liver fractions from mice (induced with Na-phenobarbital and beta-naphthoflavone) and rats (induced with Aroclor 1254) with and without G-6-PDH in the incubation mixtures. In the absence of G-6-PDH the activities were significantly lower at time 0 in the mouse. The pattern of stability, however, was similar for the activities, with an increase of stability after 1 and 2 h of pre-incubation (an exception for p-NAD). Only ED activity showed a similar behaviour in the rat. No differences were present for APD and p-NAD activities at time 0 in the rat, but the enzyme stabilities were significantly decreased after 2 h of incubation (about 15% and 10% for APD and p-NAD respectively) in the absence of G-6-PDH. At time 0, the amounts of G-6-PDH differed between mouse and rat fractions; however, during the incubations for LMA they decreased by about 57% and 53% for the two species, respectively. In addition to the above biochemical results, the presence of exogenous G-6-PDH in the incubations for the mutagenic assay, significantly increased the mitotic gene conversion and mitotic crossing-over of dimethylnitrosamine (DMN) and AR2MNFN (a nitroimidazo[2,1-b]thiazole) in the D7 strain of Saccharomyces cerevisiae.

Mutagenicity of hexachlorobutadiene, perchlorobutenoic acid and perchlorobutenoic acid chloride

Hexachloro(1,3)butadiene (HCBD) is a well known environmental contaminant. The nephrocarcinogenic potential of HCBD has been shown in long-term studies with rats. Experiments were performed to assist in determining whether this effect is mediated by epigenetic or genotoxic mechanisms and to compare the mutagenic properties of HCBD with those of its monooxidation products, perchloro-3-butenoic acid (PCBA) and perchloro-3-butenoic acid chloride (PCBAC), which are conceivable metabolites of HCBD. All 3 compounds are mutagenic to the Salmonella typhimurium tester strain TA100. The mutagenic effect is dose-dependent and parallels the chemical reactivity of the compounds. HCBD is only mutagenic in the presence of drug-metabolizing enzymes (S9 mix) with an increased protein content. The mutagenic response after incubation with PCBAC and PCBA is 2-3-fold that of HCBD. Additionally, both PCBAC and PCBA exert a mutagenic response in the absence of S9 mix. The experiments support the assumption of a genotoxic potential of HCBD.

Genotoxicity of apomorphine and various catecholamines in the Salmonella mutagenicity test (Ames test) and in tests for primary DNA damage using DNA repair-deficient B. subtilis strains (rec assay)

Apomorphine, N-nor-N-propyl-apomorphine, dopamine, L-DOPA, 6-hydroxydopamine and adrenaline were evaluated for genotoxicity using the Ames test and DNA repair-deficient and DNA repair-proficient Bacillus subtilis strains (rec assay, H17/M45; HLL3g/HJ-15). In the absence of an S9 liver homogenate, apomorphine induced frame-shift mutations in Salmonella typhimurium, mainly in strain TA1537; no indication of DNA-damaging effects in B. subtilis was observed. N-Nor-N-propyl-apomorphine was tested using strain TA1537 only and found to be mutagenic. Dopamine, L-DOPA, 6-hydroxydopamine and adrenaline were non-mutagenic when tested without S9, whereas they were all more toxic for DNA repair-deficient than for DNA repair-proficient B. subtilis strains, indicating a DNA-damaging potential. In a second set of experiments the mode of action of apomorphine and the relevance of the positive Ames test data were investigated. Glutathione in physiological concentrations reduced the mutagenic effect of apomorphine in a dose-dependent way, both in the presence and the absence of S9. S9 also reduced the mutagenicity of apomorphine. By comparing the effects of a complete S9 mix with those of a preparation without glucose-6-phosphate and NADP, it became clear that S9 also had an activating effect, overshadowed under standard conditions by its deactivating activity. Apomorphine was not mutagenic under anaerobic conditions. Superoxide dismutase and catalase reduced the mutagenic effect of apomorphine. All test conditions which reduced the mutagenic effect also inhibited the dark discoloration of the tester plates, indicating a retardation of apomorphine oxidation. It can, therefore, be concluded that oxidation of apomorphine leads to mutagenic products which induce frame-shift mutations in Salmonella typhimurium. This oxidation was prevented both by glutathione in concentrations well below physiological levels and/or by catalase and superoxide dismutase. Under these conditions, apomorphine was non-mutagenic in therapeutic concentrations as well as at higher dose levels. The possibility of genotoxic side effects occurring in patients treated with apomorphine as an emetic drug is therefore considered to be very unlikely.

An evaluation of Salmonella (Ames) test data in the published literature: application of statistical procedures and analysis of mutagenic potency

We searched the published literature for Salmonella test data on some 450 chemicals. Only 137 of more than 400 articles containing original data satisfied minimum criteria for a quantitative analysis [1751 experiments, comprising data on 152 chemicals (Table 1)]. Many of these papers did not report basic information about the test protocol (Table 2). We used previously described statistical procedures (Bernstein et al., 1982) to estimate the initial slopes of the dose-response curves and corresponding standard errors. We also applied tests for significance and linear goodness-of-fit. We then used the results of these analyses to examine several issues: (1) Linearity of the low dose region of the dose-response curve. We found that the overwhelming majority of curves were linear, though ability to detect non-linearity of dose-response curves in the standard plate test is only limited. 7% of all experiments to which the goodness-of-fit test was applied were curves of increasing slope, and with a few possible exceptions, these were not obviously associated with any particular mutagens, even those generally considered to produce non-linear effects such as MNNG and EMS (Table 3). (2) Performance of the statistical test for significance. Results of the statistical test for significance of the dose-response were compared with author's opinions as to positivity. In almost all cases (94%) results of the statistical test and authors opinions were the same. In the examples of conflicting opinions, the reasons were: (a) the statistical test places more weight than do most authors on the presence of a linear dose-response; (b) most authors tend to require at least a 2-fold increase over the spontaneous background for 'significance', and (c) when the number of spontaneous revertants is small (e.g., TA1537), authors tend to require a larger increase in induced revertants than when the spontaneous background is large, whereas the statistical procedure makes no such distinction. These factors result in the statistical test tending to identify more experiments as positive than do authors, provided there is a linear dose-response, and authors tending to judge more experiments as positive when the dose-response is not linear. (3) Reproducibility. Among the 1751 experiments there were 122 data-sets (a total of 333 experiments) in which the same chemical was tested by two or more different laboratories under the same protocol. 21 of the 122 data-sets had some disagreement between experiments as to whether results were positive or negative (Table 4).(ABSTRACT TRUNCATED AT 400 WORDS)

Mutagenicity of 2-hydroxyalkyl-N-nitrosothiazolidines

The mutagenicity of 2-hydroxyalkyl-N- nitrosothiazolidines was tested using Salmonella typhimurium strains TA98 and TA100. The N- nitrosothiazolidines tested were unsubstituted N- nitrosothiazolidine (NT), N- nitrosothiazolidine -4-carboxylic acid ( NTC ), 2-hydroxymethyl-N- nitrosothiazolidine ( HMNT ), 2-(1,2,3,4- tetrahydroxybutyl )-N- nitrosothiazolidine , 2-(1,2,3,4- tetrahydroxypentyl )-N- nitrosothiazolidine , 2-(1,2,3,4,5- pentahydroxypentyl )-N- nitrosothiazolidine ( PHPNT ) and 2-(1,2,3,4,5- pentahydroxypentyl )-N- nitrosothiazolidine -4-car boxylic acid. Among the N- nitrosothiazolidines tested, only HMNT and PHPNT exhibited clear dose-response mutagenicity toward strain TA100 with or without metabolic activation. None of the 2-hydroxyalkyl-N- nitrosothiazolidines were mutagenic to strain TA98. NT exhibited much stronger mutagenicity than either HMNT or PHPNT . Mutagenic activities of NT and PHPNT were eliminated by carboxyl substitution in the position alpha to the N-nitroso group.

Mutagen formation in browning model systems

A browning model system, consisting of diacetyl and ammonia, produced frameshift and base-pair substitution mutagens when the system was heated over 20 min and 120 min, respectively. The major product was 2,4,5- trimethylimidazole , which showed no mutagenicity toward Salmonella typhimurium strains TA98 and TA100 with or without metabolic activation. When furfural was reacted with nitrate under mild conditions (for 30 min to 3 h at 0-25 degrees C and pH 2-7), it did not produce mutagenic nitrofuran derivatives. However, the ethyl ether extract obtained from the reaction mixture of furfural and nitrate with hydrochloric acid exhibited strong mutagenic activities toward S. typhimurium strains TA98 and TA100 in the presence of metabolic activation. The major product of this reaction mixture, 4- nitrofurfural , exhibited no mutagenicity toward tester strains TA98 and TA100 with or without metabolic activation. Pure active mutagen(s) was (were) not, however, identified in either system.

Mutagenicity of pyridine- and quinoline-carbohydroxamic acid derivatives

11 pyridine- and 6 quinoline-carbohydroxamic acids were tested for mutagenicity on Salmonella typhimurium TA100 and TA98. The results are compared with those obtained for benzohydroxamic acid and 4 naphthohydroxamic acids. Most of them were mutagenic on both these tester strains. Of the pyridine derivatives, pyridine-2-carbohydroxamic acid was the most potent mutagen. Quaternarization of the pyridine-ring nitrogen prevented the induction of mutation to a marked extent. Among the quinoline derivatives, quinoline-6-carbohydroxamic acid showed potent mutagenicity similar to that of 2-naphthohydroxamic acid. The present study supports the proposal made previously that the mechanism for mutagenicity of hydroxamic acids involves Lossen rearrangement of the acid conjugates produced by enzymic acylation (or perhaps phosphorylation or sulfation) of the hydroxamic acids, followed by carbamoylation of the target molecule in the cell by the resultant isocyanate. The multiplicity of factors determining the mutagenic potency of hydroxamic acids is discussed.

Ames mutagenicity tests of products from a heated potato-starch system

A charred sample was prepared from potato starch heated with ammonium carbonate at 600 degrees C in a flask under a nitrogen stream. The water produced was collected and extracted with methylene chloride. The basic fraction obtained from the extract exhibited strong mutagenicity in Ames assays using Salmonella typhimurium strains TA98 or TA100 with metabolic activation (rat-liver S-9 mix). The basic fraction was further fractionated by silica gel column chromatography and subsequently by Sephadex column chromatography. Some of the resulting fractions exhibited strong mutagenic activities in S. typhimurium strain TA98 with S-9 mix.

Bacterial and mammalian cell mutagenesis, sister-chromatid exchange, and mouse lung adenoma bioassay with the antineoplastic acridine derivative amsacrine

Amsacrine is a DNA intercalating agent with antineoplastic properties in lymphoproliferative disorders. This report describes a group of short-term tests with multiple endpoints to characterize the mutagenic and carcinogenic properties of this drug. In vitro studies included bacterial and mammalian cell mutagenesis, and sister-chromatid exchange and chromosome aberrations in mammalian cells. In vivo, mice were given amsacrine for 7 wk at 2, 5, and 10 mg/kg and were observed for an additional 17 wk. The standard bacterial assay revealed cytotoxicity at 2000 and 5000 micrograms/plate in the preincubation assay. No significant increase in revertants occurred in Salmonella strains, except for TA1537 in the activation phase. Amsacrine at 4.0 micrograms/ml was cytotoxic to V-79 cells in the cell mutation assay, and at lower dose levels was a direct-acting mutagen for the HGPRT locus. Sister-chromatid exchange rate of Chinese hamster ovary cells was increased more than twofold at 2 micrograms/ml without metabolic activation. Cell anomalies included changes in metaphase cell kinetics and chromosome damage. Mice in the lung adenoma bioassay failed to show increased numbers of tumors, while indicating lack of tolerance and survival beyond 5 mg/kg. The results indicate clear genotoxicity to mammalian cell systems with a spectrum of changes from point mutation and SCE induction to cell-cycle alterations, irrespective of exogenous metabolic activation. These results corroborate previous findings in animal and human cell systems in vitro. The reduction of genotoxicity in bacterial assays after exogenous metabolic activation may suggest some detoxification, and the magnitude of effects observed in mammalian cells indicates that exogenous metabolic activation is not required to manifest amsacrine's activity. The lack of tumor-inducing potential in mice may be attributed to strong cytotoxic effects in this species, or to an insensitivity of the target organ, or to assay systems that may mask the carcinogenic potential.

Mutagenicity of lichen constituents

Usnic acid (the most abundant lichen constituents), physodic, and physodalic acids isolated from Hypogymnia enteromorph (Ach.) Nyl. were tested for mutagenicity in the Ames Salmonella/microsome assay. Physodalic acid exhibited clear dose-related mutagenicity against Salmonella typhimurium strain TA 100 with or without S9 mix in both plate-incorporation and preincubation assays. The addition of S9 mix increased the number of revertants approximately threefold and fourfold in preincubation and plate-incorporation assays, respectively.