The effectiveness of Salmonella strains TA100, TA102 and TA104 for detecting mutagenicity of some aldehydes and peroxides

Several aldehydes and peroxides were tested for mutagenicityusing Salmonella typhimurium tester strains TA97a, TA100, TA102and TA104, in the presence and absence of Aroclor-induced liverS9 mix from F344 rats and B6C3F₁ mice, in either preincubationor vapour phase rotocols. Some chemicals were tested in additionalSalmonella strains. Benzaldehyde, butyraldehyde, benzoyl peroxide,4-chlorobenzaldehyde, isobutyraldehyde, propionaldehyde andveratraldehyde were non-mutagenic Acetaldehyde and dicumyl peroxidegave inconsistent results and furfural gave equivocal responsesin TA100 and TA104. Cumene hydroperoxide, formaldehyde and glutaraldehydewere mutagenic in TA100, TA102 and TA104. trans-Cinnamaldehydeexhibited a weak mutagenic response in TA100 with mouse liverS9 only. 2,4,5-Trimethoxybenzaldehyde was mutagenic only instrain TA1538 with rat liver S9. With the exception of butanoneperoxide, which was mutagenic only in TA104, all chemicals mutagenicin strains TA102 and/or TA104 were also mutagenic in TA100.The data do not, therefore, support the preferential use ofstrains TA102 and TA104 for screening aldehydes and peroxidesfor mutagenicity. For a number of these chemicals the advantagesof using TA102 or TA104 was in the increased responses comparedwith those obtained with TA100. Two of the four peroxides weremutagenic and one of these was mutagenic only with TA104. Thissuggests that strains TA102 and TA104 be used if peroxides arenot mutagemc in TA100 or TA97. ⁴Present addresses: ⁴British American Tobacco Ltd, SouthamptonSO15 8TL, UK ⁵FRAME, Nottingham NG1 4EE, UK ³To whom correspondence should be addressed. Tel: +1 919 541 4482; Fax: +1 919 541 2242; Email: zeiger{at}niehs.nih.gov      

Comparative mutagenic and genotoxic effects of three antimalarial drugs, chloroquine, primaquine and amodiaquine

Comparative mutagenic and genotoxic effects of three antimalarialdrugs, chloroquine, primaquine and amodiaquine, were assessedin the Ames mutagenicity assay (in strains TA97a, TA100, TA102and TA104) and in vivo sister chromatid exchange (SCE) and chromosomeaberration (CA) assays in bone marrow cells of mice. These arethe most commonly used antimalarial drugs available at presentthroughout the world. The results of the bacterial mutagenicityassays showed a very weak mutagenic effect of all three drugsin Salmonella strains TA97a and TA100 both with and withoutS9 mix and in TA104 only with S9 mix. The results of the invivo SCE and CA assays indicate that these three drugs are genotoxicin bone marrow cells of mice. ³To whom correspodence should be addressed. Tel: +91 33 473 3491; Fax: +91 33 473 5197; Email: iichbio{at}giascl01.vsnl.net.in     

Mutagenic activity in synthetic pyrethroids in Salmonella typhimurium

Four pyrethroids, allethrin, resmethrin, permethrin and fen-valerate,were tested for mutagenicity in bacterial reversion assay systemswith seven strains (TA1535, TA100, TA1538, TA98, TA1537, TA97and TA104) of Salmonella typhimurium. Our results show thatthree pyrethroids, namely resmethrin, permethrin and fenvalerate,were not found to be mutagenic in S. typhimurium in the presenceor absence of a rat liver activation system. Allethrin was foundto be mutagenic with TA100, TA104 and TA97 strains and requiredmetabolic activation (S9 mix) in order to show its activity,mainly with TA100 and TA104 strains.     

Bacterial genotoxicity of nitrosated famotidine

Famotidine, a histamine H2-receptor antagonist, was devoid ofmutagenic activity in seven his^- Salmonella typhimurium strains(TA1535, TA1537, TA1538, TA97, TA98, TA100 and TA102) and wasequitoxic in repair-proficient (WP2) and repair-deficient (WP2uvr,WP67, CM561, CM571, WP100 and CM871) Escherichia coli strains,both in the presence and in the absence of S9 mix containingliver S9 fractions from Aroclor-treated rats. However, aftera short pre-incubation step with nitrite in an acidic environment,the drug increased, by a direct mechanism, the number of his⁺revertants in Salmonella strains TA100, TA102 and TA97 (a decreaseof mutagenicity being conversely observed in TA1535) and oftrp+ revertants in E. coli strains WPluvrA and WP67. Moreover,it enhanced the induction of non-reparable DNA damage in E.coli strains simultaneously lacking the uvrA-dependent excisionrepair and the lexA post-replication repair pathways. The mutagenicityof acidified nitrite-famotidine mixtures was related to dosesof both precursors, with a maximum production of mutagenic derivativesin a slight molar excess of nitrite. The optimal pH of the nitrosationreaction (2.0) was intermediate between the one required forcimetidine (1.5) and ranitidine (2.5). Potency of famotidineas a precursor of mutagenic derivatives was considerably lowerthan the one of the other two H₂ blockers. The nitrosation productsof all three drugs mainly induced base-pair substitutions inSalmonella DNA, to a greater extent at sites containing G-Cbase pairs (strain TA100) in the case of famotidine and cimetidine,and at sites containing AT base pairs (TA102) in the case ofranitidine. Although these experimental findings may suggestpossible toxicological consequences in ulcer patients receivinganti-secretory drugs, various considerations tend to minimizetheir practical in vivo relevance, especially for risk-benefitevaluations. Additionally, as in the case of cimetidine andranitidine, formation of mutagenic nitrosated famotidine wasefficiently prevented by equimolar ascorbic acid.     

Mutagenicity of red, wine in the L-arabinose resistance test with Salmonella typhimurium

The forward mutation assay to L-arabinose resistance (Ara test)in Salmonella typhimurium detected a Spanish red table wine(Rioja) as a direct-acting mutagen. The best mutagenic responsewas obtained by preincubating strain BA13 with the wine samplein the presence of sodium phosphate buffer and in the absenceof any external metabolic activation. In fact, the S9 mixtureabolished most of the mutagenic activity of red wine in theAra test. Such an inactivating capacity seems to be independentof microsomal enzymes and mediated through some kind of heat-stablecomponent(s) in the S9 fraction. Both regular wine (directlyfrom the bottle) and lyophilized wine were strong mutagens inthe Ara test, inducing 4914 and 2739 Ara^R mutants/ml. Both pKMlOland uvrB were critical factors in the detection of the mutagenicityof wine, exhibiting a synergic effect in strain BA13. The mutagenicityof red wine was somehow pH-dependent, increasing with the pHvalue of the preincuba-tion mixture. In comparison with theAra test, the His reverse mutation assay (Ames test) was muchless sensitive to the mutagenicity of lyophilized red wine,TA102 being the most (448 His⁺/ml) and TA98 the least (38 His⁺/ml)sensitive strain. TA100, TA104 and TA97 manifested intermediatemutagenicities to red wine. Previous reports have identifiedstrain TA98 as the His strain most sensitive to the apolar fraction(e.g. XAD-2-bound) of red wine. Based on these results we proposethat TA98 mainly detects glycosides of mutagenic flavonols presentin red wine (quercetin, rutin, etc.), which do not constitutethe major direct-acting mutagens detected with the Ara test.In contrast, the Ara test (and possibly TA102) are more sensitiveto other chemical(s) present in complete regular wine or lyophilizedwine. In this respect, it is possible that the direct-actingmutagenicity of red wine in the Ara test could be due to oxidativechemicals.     

Studies on the induction of gene mutations in bacterial and mammalian cells by the ring-opened benzene metabolites trans,trans-muconaldehyde and trans,trans-muconic acid

t,t-Muconaldehyde and t,t-muconic acid have been investigated for the induction of gene mutations in Salmonella typhimurium (reversion of the his- strains TA97, TA98, TA100, TA102, TA104 and TA1535), Escherichia coli (reversion of the trp- strain WP2 uvrA) and Chinese hamster V79 cells (acquisition of resistance toward 6-thioguanine). t,t-Muconaldehyde proved weakly mutagenic in strain TA104 in the presence and absence of NADPH-fortified postmitochondrial fraction from rat liver homogenate (S9 mix). In strains TA97, TA100 and TA102, weak positive responses were observed only in the presence of S9 mix. In strains TA98, TA1535 and WP2 uvrA, the result was negative. In V79 cells, the mutation frequency was increased from approximately 7 X 10(-6) to 90 X 10(-6) in cultures exposed to t,t-muconaldehyde at optimal concentration (1.7-3 microM in separate experiments). The concentration-response curve showed pronounced hyperlinearity, with no mutagenic effect being observed at a third of the optimal concentration. t,t-Muconic acid was greater than 100 times less toxic than t,t-muconaldehyde in both bacteria and mammalian cells, and it did not show any mutagenic effect. These results complete a previous mutagenicity study, carried out on benzene and 13 metabolites. It is concluded that the newly investigated metabolites cannot account for the bacterial mutagenicity of bioactivated benzene and benzene-trans-1,2-dihydrodiol, since these compounds exhibited their strongest response in strain TA1535. t,t-Muconaldehyde showed similarities in its mutagenicity to p-benzoquinone and hydroquinone. All three compounds showed, at most, weak effects in bacteria, but were strongly mutagenic in V79 cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mutagenic evaluation of some triazino indoles using the Salmonella/mammalian microsome assay

The mutagenicity of ethyl l,2,3-triazino[5,4-b]indole-4-carb-oxylateN(3)-oxide (D3) and 2-chloroethyl 1,2,3-triazino-[5,4-b]indole-4-carboxylateN(3)-oxide (D4), heads of series of new products with considerableplatelet antiaggregating and hypotensive activity, and theirprecursors 2-ethoxy-carbonylmethyl-l-methyUndole-3-carboxylicacid (A₃) and 2-(2-chloroethoxycarbonyhnethyl)-l-methylindole-3-carb-oxylkacid (A₄) were tested in four strains of Salmonella typhimurium(TA98, TA100, TA97 and TA102) using the standard plate incorporationtechnique. A₃ and A₄ were not mutagenic whereas D3 was mutagenicto all the strains and D₄ was mutagenic to TA97, TA98 and TA100.The addition of 4 or 10% of S9 mix decreased the mutagenic activityof both compounds. This effect was independent of the concentrationof S9 in the S9 mix.     

Comparative mutagenicity of structurally related aliphatic epoxides in a modified Salmonella/microsome assay

Four structurally related aliphatic epoxides (1,2-epoxypropane,1,2-epoxyisobutane, cis- and trans-2,3-epoxybutane) have beentested in the Salmonella/microsome assay, modified for volatilesubtances, using the strains TA1535 and TA100. The aim of thestudy was to evaluate the effect of methylation on the mutagenicityof 1,2-epoxypropane in this vaporization assay, with and withoutexogenous metabolization. All substances induced a significantincrease of revertants in the strains TA1535 and TA100. In termsof mutagenic potency, the following hierarchy was observed inthe standard tester strain TA1535 and in the absence of ratS9: 1,2-epoxypropane > cis-2,3-epoxybutane > 1,2-epoxyisobutane> trans-2,3-epoxybutane. After exogenous metabolization,the mutagenic response of 1,2-epoxyisobutane was substantiallyreduced, while a moderate decrease of cis-2,3-epoxybutane wasobserved in the presence of S9, as compared with the responsewithout S9. No influence of the S9 on the mutagenic responseof trans-2,3-epoxybutane was noticed in both strains TA1535and TA100, while an increased response with 1,2-epoxypropanewas observed in TA100 but not in TA1535. The results suggestthat the vaporization assay may provide more relevant informationconcerning mutagenic potencies of gaseous or volatile compoundsthan the common treat-and-plate or preincubation assays. Moreover,it appears that mutagenicity theories, based only upon inductiveeffects of side groups, may not suffice to explain differencesin mutagenicity. Sterical factors or differential interactionswith metabolizing enzymes could also be important in the evaluationof mutagenic effects. ⁴Present address: Ministrium für Umwelt und Gesundheit,Kaiser Friedrichstrasse 7, D-6500 Mainz, Germany      

Effects of Salmonella genotypes and testing protocols on H2O2-induced mutation

Hydrogen peroxide (H2O2) was shown to be mutagenic in a number of strains of Salmonella typhimurium. Strain SB1106p (hisC3108, hisO1242, pKM101), a newly-constructed strain carrying the histidine mutation at a UGA chain-terminating codon, was more responsive to H2O2 than TA104 or TA102, the two hisG428 strains originally developed for detecting oxidative mutagens. The largest proportional increase in revertants of strain TA104 was in the fraction of intragenic deletions. Three other strains (TA97, SB1111 and SB1106) gave unequivocal positive responses to H2O2 in both the liquid pre-incubation procedure and standard plate incorporation procedure. The response of TA100 varied among experiments, ranging from negative to a weak positive. Variations in the catalase content among the tester strains did not correlate with the relative responses obtained in the mutagenicity assays.     

Synthesis and mutagenicity of 1-nitropyrene 4,5-oxide and 1-nitro-pyrene 9,10-oxide, microsomal metabolites of 1-nitropyrene

[4,5,9,10-³H]1-Nitropyrene was incubated with liver microsomesprepared from guinea pigs treated with Aroclor 1254 and theproducts were examined by h.p.l.c. The previously reported metabolites,1-nitropyrene trans-4,5-diliydrodiol, 1-nitropyrene trans-9,10-dihydrodiol,and 3-, 6-, and 8-hydroxy-1-nitropyrene were detected. In addition,h.p.l.c., nuclear magnetic resonance and mass spectral analysesindicated the presence of 1-nitropyrene 4,5-oxide and 1-nitro-pyrene9,10-oxide. The epoxide hydrase inhibitor, 1,2-epoxy-3,3,3-trichloropropane,decreased the concentration of the 4,5- and 9,10-dihydrodiolsin the microsomal incubations and increased the concentrationof their corresponding oxides. Reaction of 1-nitropyrene withm-chloroperoxybenzoic acid gave a mixture of 1-nitropyrene 4,5-oxideand 1-nitropyrene 9,10-oxide, which was separated by chromatography.The mutagenicity of the oxides was determined in Salmonellatyphimurium strains TA98, TA98NR, and TA98/1,8-DNP₆, both withand without exogenous activation by a rat liver homogenate fraction(S9). In the absence of S9, both oxides showed maximum activityin TA98, slightly decreased mutagenicity in the acetylase-deficientstrain TA98/1,8-DNP₆, and much reduced activity in the nitroreductase-deficientstrain, TA98NR. When assayed in the presence of S9, 1-nitropyrene4,5-oxide had maximum mutagenicity in TA98, and was 50 and 95%less mutagenic in TA98NR and TA98/1,8-DNP₆, respectively. 1-Nitropyrene9,10-oxide had a similar strain sensitivity, except that itstotal mutagenicity was lower. Since 1-nitropyrene is metabolizedby oxidative pathways in vivo, these K-region oxides may contributeto the toxicities elicited by this compound. ⁴To whom correspondence should be addressed     

Mutagenic evaluation of trichlorfon using different assay methods with Salmonella typhimurium

Evaluation of the mutagenicity of trichlorfon pesticide was carried out with strains TA1535, TA100, TA97, TA98 and TA104 of Salmonella typhimurium by means of several assay methods: (i) spot test; (ii) standard plate incorporation test; (iii) plate incorporation test with preincubation; (iv) fluctuation test and (v) fluctuation test with preincubation, with and without post-mitochondrial liver fraction (S9) from Wistar rats pretreated with phenobarbital and 5,6-benzoflavone as a metabolic activation system. Trichlorfon induced base-pair substitution mutations, and its mutagenic activity was decreased by the addition of S9 mix. The fluctuation test and fluctuation test with preincubation were the most sensitive assay methods for detecting the mutagenicity of trichlorfon.     

Propyldazine is mutagenic in Salmonella typhimurium and Escherichia coli: distinct specificity for strains TA1537 and TA97

The antihypertensive drug propyldazine (Atensil) was demonstrated to be mutagenic with auxotrophic mutants of Salmonella typhimurium and Escherichia coli. Addition of liver S9 mix (postmitochondrial supernatant fraction supplemented with an NADPH-generating system) had little, if any, effect on the mutagenicity. The mutagenicity showed an unusual pattern of strain specificity. Increased frequencies of reversion were observed with all strains whose auxotrophy was caused by frame-shift mutations: the number of revertant colonies per plate from S. typhimurium TA98, TA1538, TA97, and TA1537 was increased up to 5-, 9-, 43-, and 160-fold, respectively, above background. Among the strains that became auxotrophic by substitution mutations, S typhimurium TA102, E. coli WP2, and E coli WP2 uvrA yielded positive results (twofold above background). S. typhimurium TA1535 and TA100 were not reverted by propyldazine. It should be noted that propyldazine, due to its low toxicity and good solubility, could be tested up to very high doses. Hence, although quite impressive mutagenic effects occurred, the mutagenic potency was moderate even in the most responsive strains, TA1537 and TA97 (about 0.3 and 1.0 revertants per nmole, respectively). With the limitation that the strain specificities were different, the mutagenic potency of propyldazine was in the same order of magnitude as that of hydralazine and dihydralazine, two related antihypertensive drugs which were already known to be mutagenic. In our hands, both compounds were mutagenic in S typhimurium TA1535, TA100, TA1537, and TA98. These results differ from data in the literature in that we found clear but weak effects even with strains for which others have reported negative results.     

Evaluation of the genotoxicity of stevioside and steviol using six in vitro and one in vivo mutagenicity assays

Stevioside, a constituent of Stevia rebaudiana, is commonlyused as a non-caloric sugar substitute in Japan. The genetictoxicities of stevioside and its aglycone, steviol, were examinedwith seven mutagenicity tests using bacteria (reverse mutationassay, forward mutation assay, umu test and rec assay), culturedmammalian cells (chromosomal aberration test and gene mutationassay) and mice (micronucleus test). Stevioside was not mutagenicin any of the assays examined. The aglycone, steviol, however,produced dose-related positive responses in some mutagenicitytests, i.e. the forward mutation assay using Salmonella typhimuriumTM677, the chromosomal aberration test using Chinese hamsterlung fibroblast cell line (CHL) and the gene mutation assayusing CHL. Metabolic activation systems containing 9000 g supernatantfraction (S9) of liver homogenates prepared from polychlorinatedbiphenyl or phenobarbital plus 5, 6-benzoflavone-pretreatedrats were required for mutagenesis and clastogenesis. Steviolwas weakly positive in the umu test using S.typhimurium TA1535/pSK1002either with or without the metabolic activation system. Steviol,even in the presence of the S9 activation system, was negativein other assays, i.e. the reverse mutation assays using S.typhimuriumTA97, TA98, TA100, TA102, TA104, TA1535, TA1537 and Escherichiacoli WP2 uvrA/pKM101 and the rec-assay using Bacillus subtilis.Steviol was negative in the mouse micronucleus test The genotoxicrisk of steviol to humans is discussed. ⁹To whom correspondence should be addressed     

Mutagenic potential of Indian tobacco products

The mutagenic potential of aqueous extracts of masheri (ME),chewing tobacco alone (CTE) and a mixture of chewing tobaccoplus lime (CTLE) was tested using the Ames assay. ME exhibitedmutagenicity in Salmonella typhimurium TA98 upon metabolic activationwith aroclor-1254-induced rat liver S9, while nitrosation renderedit mutagenic in TA100 and TA102. CTE exhibited borderline mutagenicityin the absence or presence of S9 in TA98 and TA100 and afternitrosation in TA102, while nitrosation led to doubling of TA98and TA100 revertants. In contrast, CTLE exhibited direct mutagenicityin TA98, TA100 and TA102, was mutagenic to TA98 upon S9 additionand induced mutagenic responses in all three tester strainsafter nitrosation. Experiments using scavengers of reactiveoxygen species (ROS) suggested that CTLE-induced oxidat-ivedamage in TA102 was mediated by a variety of ROS. The high mutagenicpotency of CTLE vis à vis that of CTE may be attributedto changes in the pH leading to differences in the amount andnature of compounds extracted from tobacco. Thus, exposure toa wide spectrum of tobacco-derived mutagcns and promutagensmay play a critical role in the development of oral cancer amongusers of tobacco plus lime. ¹To whom correspondence should be addressed     

The effect of biotransformation of 2,4-dinitrotoluene on its mutagenic potential

Because both oxidative and reductive metabolism of the hepatocarcinogen2,4-dinitrotoluene (2,4-DNT) can occur in vivo; we have examinedthe mutagenicity of compounds which can be formed from 2,4-DNTin an attempt to establish which metabolic pathways contributeto the formation of genotoxic products. A quantitative reversionassay using Salmonella typhimurium TA98 was used to evaluatethe mutagenicity of these compounds. 2,4-Dinitrobenzyl alcohol,2-amino-4-nitro-toluene and 2-nitroso-4-nitrotoluene were foundto be more mutagenic to S. typhimurium than is 2,4-DNT and didnot require metabolic activation by post-mitochondrial super-natantsof Aroclor-induced rat liver homogenates (S9) for their effect.2-Amino-4-nitrobenzoic acid was also mutagenic to S. typhimuriumTA98 in the absence of S9, but its mutagenicity was enhancedwhen S9 was included in the incubation mixture. 2,4-Diaminotoluenerequired S9 for demonstration of mutagenicity and was approximatelyas effective, on a molar basis, as 2,4-DNT in inducing reversionto histidine prototrophy. These results suggest that both oxidativeand reductive metabolism may be involved in production of mutagenicmetabolites of 2,4-DNT. ¹Present address to which correspondence should be addressed:Department of Pharmacology and Toxicology, University of MississippiMedical Center, 2500 N. State Street, Jackson, MS 39216, USA      

Re-evaluation of the effect of ellagic acid on dimethylnitrosamine mutagenicity

Dimethylnitrosamine (DMN) is activated to mutagenic speciesin the Ames test (Salmonella typhimurium strain TA 100) by hamsterhepatic S9 preparation. This S9 activity is induced by administrationof ethanol to the animals. The organic solvents dimethylsulphoxide(DMSO) and N-methyl-2-pyrrolidinone (MP) inhibit this mutagenicity,apparently because they inhibit DMN demethylase activity (assayedas formaldehyde production). Ellagic acid, dissolved in DMSOor MP, had no inhibitory effect on DMN mutagenicity, beyondthe effect of the solvent vehicle. ²To whom correspondence should be addressed     

Evaluation of the genotoxicity of gentian violet in bacterial and mammalian cell systems

Previous studies indicate that gentian violet (GV), a triphenylmethane dye used in agriculture and human medicine, is a clastogen in vitro and a carcinogen in chronically exposed mice and rats. Data on its genotoxic activity, however, have been incomplete and partly contradictory. Mutagenesis and DNA damage experiments were conducted to re-evaluate the genotoxic potential of GV in both bacterial and mammalian cell systems. GV was mutagenic in Salmonella typhimurium tester strains TA97 and TA104, but there was little mutagenic activity detected in strains TA98 and TA100. A rat liver homogenate fraction (S9) tended to increase mutagenicity. The major microsomal metabolites of GV, pentamethylpararosaniline and N,N,N',N'-tetramethylpararosaniline were less mutagenic in TA97 and TA104, while N,N,N',N"-tetramethylpararosaniline was a weak mutagen in Salmonella. GV was not mutagenic in Chinese hamster ovary (CHO) cell strain CHO-K1-BH4, and was a questionable mutagen in CHO-AS52 cells. While GV produced DNA damage as measured by sedimentation of nucleotids derived from B6C3F1 mouse lymphocytes treated in vitro, no damage was found in lymphocytes isolated from mice dosed with GV. GV was also a weak producer of gene amplification in an SV40-transformed Chinese hamster cell line. The results indicate that GV is a point mutagen in bacteria; however, since similar exposure conditions produced weak mutagenic activity in mammalian cells, GV may be carcinogenic by virtue of its clastogenic activity.     

Influence of the triazine ring on the mutagenicity of triazinoindoles and some congeners.

Three compounds, which could be considered as precursors or derivatives of the 3-(4'-substituted-benzylidenamino)5H- 1,2,3-triazin[5,4b]indol-4-one series, were selected from the study of their mutagenic activity. Ames tests were performed study of their mutagenic activity. Ames tests were performed using the Salmonella typhimurium strains TA97, TA98, TA100, and TA102, according to the preincubation procedure, both with and without metabolic activation. The 3-amino-5H-1,2,3-triazin[5,4b]indol-4-one has been shown to be a strong S9-independent mutagen, which reverts frameshift and substitution mutations. Nevertheless its potency increases with the addition of microsomal fraction. In contrast, the 2-benzyliden-1-(3-aminoindol)-2-carbohydrazide and the 3-aminoindol-2-carbohydrazide congeners were not mutagenic. These results suggest that the 1,2,3-triazine ring is the principle substructure responsible for the mutagenicity of the triazinoindole congeners studied.     

Mutagenicity testing of rutacridone epoxide and rutacridone, alkaloids in Ruta graveolens L., using the Salmonella/microsome assay

The mutagenicity of rutacridone and rutacridone epoxide wasinvestigated using Salmonella typhimurium without as well aswith different metabolic activation systems. Rutacridone epoxidewas found to be a direct acting mutagen in S. typhimurium strainsTA98, TA100 and TA1538; addition of rat liver preparations resultedin a marked decrease of mutagenicity. In contrast, rutacridonerequired metabolic conversion to exhibit mutagenic activity.Neither of the compounds had any effect on tester strain TA1978.S9 mixes as well as microsomal and cytosolic preparations fromuntreated, phenobarbital-treated and 3-methylcholanthrene-treatedrats were used to study the activation and deactivation capacitiesof the enzyme mixtures. In addition, the influence of enzymeinhibitors on the activation and deactivation of the furoacridoneswere tested. Evidence is presented that rutacridone is metabolizedby rat liver enzymes to the corresponding epoxide as the ultimatemutagen. ^*Dedicated to Professor Dr C.-G.Arnold on the occasion of his60th birthday.      

Methylglyoxal: genotoxicity studies and its effect in vivo on the hepatic microsomal mono-oxygenase system of the mouse

The genotoxic potential of methylglyoxal (MG) was studied inSaccharomyces cerevisiae D7 and in Salmonella typhimurium TA97and TA102 in the presence and in the absence of metabolic activationsystem (S9 fraction) prepared from mouse liver induced withß-naphthoflavone (ß-NF) and sodium phenobarbital(PB). The in vivo effects on the hepatic microsomal mixed functionmono-oxygenase system induced by MG were studied in untreated,ß-NF or PB pre-treated mice. MG was a direct-actingmutagen in S. typhimurium TA97 and TA102 when tested up to amaximum concentration of 0.47 mg/plate. Mitotic gene conversionwas also induced by MG in the yeast S. cerevisiae D7. A weakbut significant effect on reverse point mutation was also foundin S. cerevisiae. Genetic activity was lower in the presenceof S9 fraction in yeast test. In the in vivo studies, MG (atthe total dose of 600 mg/kg) was shown to increase the aminopyrineN-demethylase (APD) and p-nitroanisole O-demethylase (p-NAD)activities in uninduced mice. Cytochrome P-450 content (cytP-450) and ethoxycoumarin O-deethylase activity (ECD) were alsoweakly enhanced by MG treatment. In contrast, no significantchanges in mono oxygenase activities were seen in ß-NF-or PB-treated mice after MG injection. ¹To whom correspondence should be addressed