Absence Of S9 Activation Research Articles

Mutagenicity and Genotoxicity Assessment of Leuconostoc lactis DMLL10 Isolated from Kimchi.

Leuconostoc lactis DMLL10 is a microorganism specific to kimchi fermentation. In this study, we sought to evaluate the toxicity of this strain, which was newly isolated from kimchi, to determine its safety as a food ingredient. Bacterial reverse mutation assay, chromosomal aberration assay, and mammalian cell in vitro micronucleus assay were performed to assess the genetic toxicity of Leu. lactis DMLL10. The strain did not induce mutagenicity in Salmonella typhimurium TA98, TA100, TA1535, TA1537, or Escherichia coli WP2uvrA, with or without metabolic activation of S9 mixture. The oral administration of Leu. lactis DMLL10 also did not significantly increase the number of micronucleated polychromatic erythrocytes, or the mean ratio of polychromatic to total erythrocytes. Additionally, Leu. lactis DMLL10 did not cause a significant chromosomal aberration in CHU/IL cells in the presence or absence of S9 activation. Therefore, Leu. lactis DMLL10 can be suggested as a functional food ingredient with reliability and safety.

HPLC-ESI-QqQ based standardization, mutagenic and genotoxic potential of methanol extract of Ziziphus mauritiana Lam leaves.

The leaves of Ziziphus mauritiana Lam have been an integral part of the traditional system of medicine for the treatment of inflammation, wounds, fever, asthma and liver disorders. The leaves are utilised as an edible vegetable in rural parts of India and Indonesia. Despite its pharmacological significance, Ziziphus mauritiana Lam lacks scientific evidence on its mutagenic and genotoxic potential. The aim of the present work is to identify bioactive compounds present in the methanol extract of Ziziphus mauritiana Lam leaves (MEZ) using HPLC-ESI-QqQ and to evaluate its mutagenic and genotoxic potential. The phytochemical standardization of the MEZ was done using HPLC-ESI-QqQ. The mutagenic and genotoxic potential of MEZ was tested using bacterial reverse mutation (Ames test), chromosomal aberration, and micronucleus tests. The Ames test was performed in Salmonella typhimurium strains TA98, TA100, TA102, TA1535 and TA1537, and the genotoxic potential was tested in in-vitro using chromosome aberration assay with Chinese hamster ovary (CHO) cells and in-vivo micronucleus test using mouse bone marrow cells. Fifteen phytochemical compounds were identified in HPLC-ESI- QqQ. It was observed from the Ames test that MEZ did not induce gene mutations in the S. typhimurium in the presence or absence of S9 activation. Similarly, no significant increase in the number of structural aberrations was observed in CHO cells with or without S9 activation. The oral administration of MEZ at a dose of up to 2000 mg/kg caused no significant increase in the number of micronucleated polychromatic erythrocytes or in the mean ratio of polychromatic to total erythrocytes. The findings of the present study confirm that MEZ is not-mutagenic and non-genotoxic in the presence or absence of the exogenous metabolizing system.

An oral toxicity test in rats and a genotoxicity study of extracts from the stems of Opuntia ficus-indica var. saboten

BackgroundOpuntia ficus-indica var. saboten (OFIS) is used widely in Korea to treat constipation due to its diuretic effects and its enhancement of bowel function and appetite. However, its safety has not yet been established. The aim of this study was to evaluate the repeated oral toxicity and genotoxicity of OFIS extract (OE).MethodsWhite female and male Sprague Dawley rats (n = 6) were divided into 4 groups, and OE was administered to them orally (0, 500, 1000, and 2000 mg/kg/day, respectively) for one week. The Ames test, the chromosomal aberration assay, and the mammalian micronucleus test were performed to determine the OE genotoxicity. The Ames test was conducted using Salmonella typhimurium (S. typhimurium) strains TA100, TA1535, TA98, and TA153 and Escherichia coli (E. coli) WP2 urvA, and Chinese hamster lung (CHL) cells were used for the chromosomal aberration assay. The mammalian micronucleus test was performed using mouse bone marrow cells.ResultsThis study revealed that OE administration did not alter the normal rat behavior, body weight gain, and food and water consumption with respect to the normal controls. In addition, there were no toxic effects observed during the ophthalmological test. The biochemical hematological and serum values as well as urinalysis parameters and organ weights were all similar to those of the normal control group. In addition, no mutagenicity effects from the OE were found in S. typhimurium or E. coli with or without S9 activation according to the Ames test. The OE did not significantly alter the number of structural aberrations in the CHL cells in the presence or absence of S9 activation. The oral administration of OE also caused no significant increase in the number of micronucleated polychromatic erythrocytes or in the mean ratio of polychromatic to total erythrocytes.ConclusionsIn conclusion, OE could be considered as a reliable and safe herbal medicine or functional food since no toxicity was found under the conditions of this study.

UV-irradiated 2-methyl-4′-(methylthio)-2-morpholinopropiophenone-containing injection solution produced frameshift mutations in the Ames mutagenicity assay

In previous studies, we detected the photoinitiators 1-hydroxycyclohexyl phenyl ketone (1-HCHPK), methyl 2-benzoylbenzoate (MBB), and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP) in intravenous injection solutions. In addition, we reported that 1-HCHPK, MBB, and MTMP exhibited cytotoxicity towards normal human peripheral blood mononuclear cells. A previous in vitro study reported that a free-radical photoinitiator introduced covalently bound purine residues into DNA. However, little is known about the in vitro mutagenicity of 1-HCHPK, MBB, and MTMP. In the present in vitro study, we evaluated the mutagenicity of 1-HCHPK, MBB, and MTMP using the Ames test. We found that untreated 1-HCHPK, MBB, and MTMP were not mutagenic in S. typhimurium strain TA97, TA98, TA100, TA102, or TA1535, regardless of the presence/absence of S9 activation. However, ultraviolet (UV) light-irradiated MTMP exhibited mutagenicity in S. typhimurium strain TA97 in the absence of S9 activation. In conclusion, we suggest that exposure to UV-irradiated MTMP, including in intravenous injection solutions, can result in frameshift mutations.

Genotoxicity evaluation of Guibi-Tang extract using an in vitro bacterial reverse mutation assay, chromosome aberration assay, and in vivo micronucleus test.

BackgroundGuibi-Tang is a traditional herbal prescription made from 12 different herbs that is used in the treatment of amnesia and poor memory.MethodsIn the present study, we evaluated the acute oral toxicity and genotoxic potential of Guibi-Tang water extract (GBT) at doses up to 2000 μg/plate an using a bacterial reverse mutation test (Ames test) with Salmonella typhimurium strains TA100, TA1535, TA98, and TA1537, and Escherichia coli strain WP2uvrA. Acute toxicity and genotoxic potential were measured in the presence and absence of an exogenous source of metabolic activation, in an in vitro chromosome aberration assay with Chinese hamster lung (CHL) cells, and in an in vivo micronucleus test using ICR mice bone marrow as recommended by the Korean Food and Drug Administration. An acute oral toxicity test of GBT was performed in Sprague Dawley rats. The Ames test showed that GBT did not induce gene mutations in S. typhimurium or in E. coli in the presence or absence of S9 activation.ResultsGBT did not significantly increase the number of structural aberrations in CHL cells with or without S9 activation. The oral administration of GBT at a dose of up to 2000 mg/kg caused no significant increase in the number of micronucleated polychromatic erythrocytes or in the mean ratio of polychromatic to total erythrocytes.ConclusionsHowever, as we did not identify the components of GBT responsible for these effects, other assays are needed to confirm its genotoxicity.

Genotoxicity and acute and subchronic toxicity studies of a standardized methanolic extract of Ficus deltoidea leaves

OBJECTIVE:Ficus deltoidea leaves have been used in traditional medicine in Southeast Asia to treat diabetes, inflammation, diarrhea, and infections. The present study was conducted to assess the genotoxicity and acute and subchronic toxicity of a standardized methanol extract of F. deltoidea leaves.METHODS:Sprague Dawley rats were orally treated with five different single doses of the extract and screened for signs of toxicity for two weeks after administration. In the subchronic study, three different doses of the extract were administered for 28 days. Mortality, clinical signs, body weight changes, hematological and biochemical parameters, gross findings, organ weights, and histological parameters were monitored during the study. Genotoxicity was assessed using the Ames test with the TA98 and TA100 Salmonella typhimurium strains. Phytochemical standardization was performed using a colorimeter and high-performance liquid chromatography. Heavy metal detection was performed using an atomic absorption spectrometer.RESULTS:The acute toxicity study showed that the LD50 of the extract was greater than 5000 mg/kg. In the subchronic toxicity study, there were no significant adverse effects on food consumption, body weight, organ weights, mortality, clinical chemistry, hematology, gross pathology, or histopathology. However, a dose-dependent increase in the serum urea level was observed. The Ames test revealed that the extract did not have any potential to induce gene mutations in S. typhimurium, either in the presence or absence of S9 activation. Phytochemical analysis of the extract revealed high contents of phenolics, flavonoids, and tannins. High-performance liquid chromatography analysis revealed high levels of vitexin and isovitexin in the extract, and the levels of heavy metals were below the toxic levels.CONCLUSION:The no-observed adverse effect level of F. deltoidea in rats was determined to be 2500 mg/kg.

Modulatory Effects of Capsaicin on N-diethylnitrosamine (DEN)-induced Mutagenesis in Salmonella typhimurium YG7108 and DEN-induced Hepatocarcinogenesis in gpt Delta Transgenic Rats

Capsaicin from the red chili pepper is a prospective chemopreventive agent. To explore the possible antigenotoxic effects of capsaicin on N-diethylnitrosamine (DEN)-induced mutagenesis in vitro, we conducted bacterial mutation assays with Salmonella typhimurium YG7108, a sensitive strain to mutagenic alkylating agents. Capsaicin was not mutagenic either with or without S9 activation. Unexpectedly,it enhanced the mutagenicity of DEN in the presence of S9 activation significantly. Capsaicin also enhanced the mutagenicity of 2-aminoanthracene and benzo[a]pyrene in the presence of S9 activation and benzo[a]pyrene diolepoxide in the absence of S9 activation. However, it reduced the mutagenicity of ethylnitrosourea in the absence of S9 activation. To examine whether capsaicin modulates DEN-induced mutagenesis and hepatocarcinogenesis in vivo, we took advantage of gpt delta rats, transgenic rodents that carry reporter genes for mutations. Female gpt delta rats were given drinking water containing 40 ppm DEN for five weeks. They were fed diets containing capsaicin at doses of 0, 100 or 500 ppm for seven weeks, starting one week before the DEN treatment. Samples were collected at weeks 7 and 32, respectively, for mutagenicity and carcinogenicity assays. DEN enhanced gpt mutant frequency more than 200 fold in the liver. However, capsaicin displayed no modulating effects on the mutagenesis. Rather, it reduced the number of liver neoplasms, especially liver cell adenomas, in a dose-dependent manner although the reduction in hepatocellular carcinoma was statistically insignificant. These results suggest that chemopreventive effect of capsaicin against DEN-induced hepatocarcinogenesis is slight and that the effect is not due to antimutagenesis. The results also caution that chemopreventive effects of chemicals should be examined not only in vitro but also in vivo with multiple indexes, e.g., in vitro and in vivo mutations and pathological examinations.

Chromium picolinate does not produce chromosome damage in CHO cells

Chromium picolinate (CrPic, Chromax ®) is a dietary supplement that has been commercially available for the past two decades. CrPic has potential benefits for reducing insulin dependence in diabetics by increasing sensitivity of insulin receptors and in stimulating insulin binding. In this study, CrPic was tested for its ability to produce chromosomal aberrations in vitro using Chinese hamster ovary K1 (CHO) cells. CHO cells were exposed to a range of cytotoxic to non-cytotoxic concentrations of CrPic for 4 or 20 h in the absence of metabolic (S9) activation or for 4 h in the presence of S9 activation. CrPic was solubilized with dimethyl sulfoxide (DMSO) to attain the highest possible solubility for maximizing the test doses. Cells were treated with 96.25, 192.5, 385 or 770 μg/mL of CrPic for 4 h in the presence of S9 activation, and for 4 or 20 h in the absence of S9 activation. A distinct precipitate of CrPic was evident in the cell culture medium at 770 μg/mL, which was the highest dose tested. Results showed no statistically significant increases in structural or numerical chromosome aberrations were produced at any test dose level with CrPic in 4-h treatments up to a precipitating dose of 770 μg/mL in either the presence or absence of S9 activation. Additionally no aberrations were observed up to 385 μg/mL (the maximum analyzable dose) following treatment for 20 h in the absence of S9 activation. The percentage of cells with structural or numerical aberrations in CrPic treated cultures was not statistically different ( p > 0.05) from that quantified in controls at any dose level. The absence of significant differences from control levels demonstrates that CrPic did not induce structural or numerical chromosome aberrations up to doses that were insoluble in the culture medium.

Acute, Subchronic, and Mutagenicity Studies with Norbornene Fluoroalcohol

The object of this study was to evaluate the toxicity of norbornene fluoroalcohol (NBFOH), which is used as an intermediate in the production of fluorinated monomers and polymers. NBFOH was evaluated for acute oral, dermal, and inhalation toxicity, dermal sensitization using the Local Lymph Node Assay (LLNA), mutagenesis by the Ames assay, and subchronic toxicity in a 4-week inhalation rat study. NBFOH demonstrated slight acute toxicity in oral, dermal, and inhalation studies. Approximate lethal doses of 3400 and > 5000 mg/kg for the oral and dermal routes, respectively, and an approximate lethal concentration of 4300 mg/m3 were determined. NBFOH demonstrated moderate skin irritation, was a severe eye irritant, produced dermal sensitization, but did not cause bacterial mutagenicity either in the presence or absence of S9 activation. Male and female rats were exposed nose only to airborne NBFOH at levels of 0, 410, 1400, and 1500 mg/m3, 6 h/day, 5 days/week for 4 weeks with clinical and histopathology specimens collected 1 day after the final exposure. Due to the vapor pressure of NBFOH, the 1500 mg/m3 atmosphere was 27% aerosol and 73% vapor; the 1400 mg/m3 atmosphere was 5% aerosol and 95% vapor, and the 410 mg/m3 level was only vapor. No test substance–related mortality or clinical signs of toxicity were observed over the course of the study, and male rats demonstrated significant weight loss and decreased food consumption at 1400 mg/m3. Male rats from the 1500 mg/m3 group demonstrated an 11% increase in prothrombin time that was significantly higher than the control value. Examination of fluoride in the urine did not demonstrate a concentration–response relationship, with minimal elevations observed in male rats at all exposure levels and sporadic increases in females. Both male and female rats exposed to 1400 mg/m3 or greater had squamous metaplasia of the laryngeal mucosa and degeneration of the nasal olfactory and respiratory mucosa. Based on the above findings, NBFOH demonstrates the potential to produce allergic contact dermatitis, and subchronic inhalation studies indicate a no-observed-adverse-effect-level (NOAEL) of 410 mg/m3.

Re-evaluation of the mutagenic potential of quinacrine dihydrochloride dihydrate

Quinacrine has been used for voluntary female non-surgical sterilization for its ability to produce tubal occlusion. Safety issues regarding quinacrine have been raised because it has been shown to intercalate with DNA. Therefore, safety issues need to be resolved by appropriate toxicology studies to support a review for human transcervical use. Such toxicology studies include mutagenicity assays. Here we report an evaluation of the genotoxicity of quinacrine dihydrochloride dihydrate (QH) using a battery of assays. In the bacterial mutagenicity assay, QH was strongly positive in Salmonella typhimurium tester strain TA1537 with and without S9-activation and in S. typhimurium tester strain TA98 with S9-activation; QH was also strongly positive in Escherichia coli WP2 uvrA without S9-activation. QH was not mutagenic in S. typhimurium tester strains TA100 and TA1535 with and without S9-activation. QH was mutagenic in the mouse lymphoma assay in the absence of S9-activation. QH was clastogenic in Chinese hamster ovary (CHO) cells, with and without S9-activation. QH was negative for polyploidy in the same chromosome aberration test. Using a triple intraperitoneal injection treatment protocol in both male and female mice, QH was negative in the in vivo mouse micronucleated erythrocyte (micronucleus) assay. These results confirm that QH is mutagenic and clastogenic in vitro and suggest a potential risk to human health due to QH exposure after intrauterine exposure.

Genotoxic substances in the St. Lawrence system I: Industrial genotoxins sorbed to particulate matter in the St. Lawrence, St. Maurice, and Saguenay rivers, Canada

AbstractPrevious investigations of organic genotoxins in industrial effluents discharged into the St. Lawrence Rivers system (Quebec, Canada) indicated that a substantial fraction of the genotoxicity is adsorbed to suspended particulate matter. This study used the SOS Chromotest to investigate the presence, potency, and behavior of particle‐bound genotoxins in the downstream ecosystem. The results indicate that although extracts of both suspended and sedimented particulate matter are genotoxic, suspended particulate matter samples are more potent in the absence of S9 activation, with the reverse being true for bottom sediments. The results confirmed a positive relationship between the genotoxicity of bottom sediment extracts and sediment organic matter content. A similar relationship between organic matter content and total polycyclic aromatic hydrocarbon (PAH) concentration indicates that putative genotoxins have physicochemical properties similar to the PAH class of contaminants. Conversion of PAH values to benzo[a]pyrene equivalents indicates that measured PAHs only account for a small fraction (∼10%) of the observed SOS Chromotest response. Sites that receive discharges from foundries, aluminum refineries, and petroleum refineries yielded several of the most genotoxic samples. Further analyses revealed that the genotoxicity of suspended and sedimented particulate matter extracts is empirically related to the genotoxicity of industrial discharges. Comparisons of total genotoxicity levels in suspended particulates and bottom sediments suggest that direct‐acting substances adsorbed to suspended matter are rapidly degraded and/or converted to more stable progenotoxins upon deposition. Further research is required to test this hypothesis and investigate effects on indigenous biota.

Comparative mutagenicity testing of ceftiofur sodium: III. Ceftiofur sodium is not an in vivo clastogen

Ceftiofur has been previously shown (Aaron et al., 1995a Mutation Res., this issue) to produce chromosome aberrations following extended treatment of Chinese hamster ovary cells in culture at high doses in the absence of S9 activation. The experiments described here address the relevance of this finding in vivo. Ceftiofur failed to induce aberrations in the bone marrow of CD-1 mice following intraperitoneal injection. Furthermore, ceftiofur did not induce micronucleated polychromatic erythrocytes in mouse bone marrow. In the experiments reported here no evidence of the induction of unscheduled DNA synthesis in the liver of rats treated in vivo was seen following oral exposure to high doses of the drug. However, the compound was foud to reach the bone marrow compartment in these experiments. Thus, the negative finding suggests that the in vitro finding of chromosome aberration induction by ceftiofur is not a cause of concern. This assertion is supported by mechanistic studies (Aaron et al., 1995b, Mutation Res., this issue) which show the cause of the in vitro findings to be most likely due cell cycle delay and by the observation that ceftiofur is rapidly metabolized in mammalian systems in vivo but not in the artificial conditions that occur in the in vitro experiments.

Microsomal metabolism of 1-nitrobenzo[e]pyrene to a highly mutagenic K-region dihydrodiol.

Aerobic metabolism of 1-nitrobenzo[e]pyrene (1-nitro-BeP) by rat liver microsomes produced 1-nitro-BeP trans-4,5-dihydrodiol, 6-hydroxy-1-nitro-BeP, and 8-hydroxy-1-nitro-BeP. When 3,3,3-trichloropropylene 1,2-oxide was incorporated into the metabolism, 1-nitro-BeP 4,5-oxide was the predominant metabolite, and 1-nitro-BeP trans-4,5-dihydrodiol was not detected. All of the metabolites were purified by both reversed- and normal-phase HPLC and characterized by analysis of their mass and 500 MHz proton NMR spectral data. 1-Nitro-BeP was not metabolized under hypoxic conditions. 1-Nitro-BeP and its four metabolites were assayed in Salmonella typhimurium tester strains TA98, TA98NR and TA98/1,8-DNP6, both in the presence and absence of S9 activation. As predicted, 1-nitro-BeP was a weak mutagen without S9 (2 revertants/micrograms in TA98); the addition of S9 resulted in approximately 18, 17 and 4 revertants/micrograms in TA98, TA98NR and TA98/1,8-DNP6 respectively. The two phenolic metabolites were mutagenic both in the presence and absence of S9, producing moderate responses (19-84 revertants/micrograms). In addition, while the 1-nitro-BeP 4,5-oxide was only weakly mutagenic in TA98 (6-14 revertants/micrograms), 1-nitro-BeP trans-4,5-dihydrodiol was unexpectedly potent (approximately 300 revertants/micrograms both with and without S9). These results indicate that microsomal epoxidation of 1-nitro-BeP followed by epoxide hydrolase-catalyzed hydrolysis of the resulting epoxide to the 1-nitro-BeP trans-4,5-dihydrodiol results in the most potent mutagenic derivatives. The weak mutagenicity of 1-nitro-BeP 4,5-oxide demonstrates that not all epoxides of nitrated polycyclic aromatic hydrocarbons (PAHs) are more mutagenic than the corresponding parent nitro-PAHs. Also, the lower S9-mediated mutagenicity of 1-nitro-BeP in TA98/1,8-DNP6 compared with TA98 indicates that the mutagenicity of 1-nitro-BeP is dependent upon nitroreduction and transesterification. Finally, we previously hypothesized that nitrated PAHs with their nitro substituents perpendicular or nearly perpendicular to the aromatic rings are very weak or nondirect-acting mutagens in Salmonella typhimurium tester strains. The results reported in this communication demonstrate that ring-oxidized derivatives of nitro-PAHs do not always follow this structure--mutagenicity correlation.

Evaluation of the L5178Y mouse lymphoma cell mutagenesis assay: Interlaboratory reproducibility and assessment

The L5178Y mouse lymphoma cell mutagenesis assay is used to detect the mutagenic activity of chemicals in a mammalian cell system. To evaluate this assay we compared the results of assays performed independently on 63 chemicals by laboratories at SRI International and Litton Bionetics, Inc. The two laboratories used similar protocols. The solvent and positive control mutant frequencies and cloning efficiencies obtained by the two laboratories were similar, which justified the use of the same quality-control criteria and analytical procedures for analyzing the results from both laboratories. The rate of concordance between the two laboratories was 92% for tests in the absence of S9 activation and 95% for tests in its presence. The results of the assays agreed for 57 of the 63 chemicals; three chemicals could not be compared because there were questionable calls in at least one of the laboratories; the results disagreed for the three remaining chemicals. The concordance rate for these overall assay evaluations was 95%. The interlaboratory concordance rates were similar to concordance rates for replicate experiments within the laboratories (96% at LBI, 94% at SRI). The mouse lymphoma cell mutagenicity results are concordant with the rodent chronic assay results in 78% of 50 chemicals and with the Salmonella assay results in 79% of 56 chemicals. Fifteen carcinogens were examined for genotoxic effects in mouse lymphoma, Salmonella, Chinese hamster ovary (CHO) chromosomal aberration, and CHO sister chromatid exchange assay. Eight of these were positive in all four assays. Of the seven noncarcinogens that were tested in these four assays, none was negative in all four. The main conclusion to be drawn from this study is that the mouse lymphoma cell forward mutation assay, as performed and evaluated in this study, detects chemical mutagenicity in a manner that is highly consistent with other genetic endpoints as well as rodent carcinogenicity studies. Thus the assay quality control and response criteria established in this study led not only to a high degree of reproducibility but also to an apparently reliable detection of mutagenic activity.

Induction of bacterial mutations by aminopyrazoles, compounds which cause mammary cancer in rats.

An aminopyrazole PD 71627 (5-amino-1,3-dimethyl-1H-pyrazol-4-yl) (2-fluorophenyl)methanone, and two amide derivatives, PD 108298, N-[4-(2-fluorobenzoyl)-1,3-dimethyl-1H-pyrazol-5-yl]-2- ([3-(2-methyl-1- piperidinyl)-propyl]amino) acetamide-(Z)-2-butanedioate (1:2), and PD 109394, 2-(diethylamino)-N-[4-(2- fluorobenzoyl)-1,3-dimethyl-1H-pyrazol-5-yl]acetamide hydrochloride, proposed neuroleptic drugs, were found to elicit mammary adenocarcinomas in male rats after 13 weeks of treatment. These compounds were assessed for their ability to induce His+ revertants (rev) in five strains of Salmonella typhimurium (TA98, TA100, TA1535, TA1537 and TA1538) in the presence and absence of S9 activation. All were found to be potent mutagens in TA98 and TA100 after a 20 min pre-incubation with Aroclor 1254-induced rat liver S9. However, the activity of the amino-pyrazole PD 71627 was much greater than the amide derivatives, PD 108298 or PD 109394, with activity of 11,800 rev/mumol, 670 rev/mumol, and 230 rev/mumol respectively in TA100, the strain showing the greatest response. A comparison of liver S9 fractions from rats untreated or pretreated with phenobarbital (PB) or Aroclor 1254 showed that S9 from animals pretreated with PB provided the greatest activation capability for the aminopyrazole PD 71627 (59,300 rev/mumol in TA100). Three structural analogs of the aminopyrazole PD 71627, two without the amine and one with a methyl substituent on the amine, were compared with PD 71627 for induction of revertants in TA100 and TA98. The compounds without the amine had no mutagenic activity while the methyl derivative induced 3100 rev/mumol in TA100 after preincubation with Aroclor 1254-induced S9. This confirmed that the amine on the pyrazole ring was required for mutagenic activity. The results of these studies support the hypothesis that these compounds cause cancer in animals as a result of DNA damage.

Mutagenicity of nitrosodiethanolamine on salmonella typhimurium

Nitrosodiethanolamine was examined in the Ames assay for bacterial mutagens. In absence of S9 activation a mutagenic effect was found.