Mutagenicity studies on ketone solvents: methyl ethyl ketone, methyl isobutyl ketone, and isophorone

3 ketone solvents (methyl ethyl ketone (MEK), methyl isobutyl ketone (MiBK), and isophorone) were tested for potential genotoxicity. The assays of MEK and MiBK included the Salmonella/microsome (Ames) assay, L5178Y/TK+/- mouse lymphoma (ML) assay, BALB/3T3 cell transformation (CT) assay, unscheduled DNA synthesis (UDS) assay, and micronucleus (MN) assay. Only the ML, UDS, and MN assays were conducted on samples of isophorone. No genotoxicity was found for MEK or isophorone. The presence of a marginal response only at the highest, cytotoxic concentration tested in the ML assay, the lack of reproducibility in the CT assay, and clearly negative results in the Ames assay, UDS and MN assays, suggest that MiBK is unlikely to be genotoxic in mammalian systems.     

Genotoxicity assessment of ethylenediamine dinitrate (EDDN) and diethylenetriamine trinitrate (DETN)

Ethylenediamine dinitrate (EDDN) and diethylenetriamine trinitrate (DETN) are relatively insensitive explosive compounds that are being explored as safe alternatives to other more sensitive compounds. When used in combination with other high explosives they are an improvement and may provide additional safety during storage and use. The genetic toxicity of these compounds was evaluated to predict the potential adverse human health effects from exposure by using a standard genetic toxicity test battery which included: a gene mutation test in bacteria (Ames), an in vitro Chinese Hamster Ovary (CHO) cell chromosome aberration test and an in vivo mouse micronucleus test. The results of the Ames test showed that EDDN increased the mean number of revertants per plate with strain TA100, without activation, at 5000μg/plate compared to the solvent control, which indicated a positive result. No positive results were observed with the other tester strains with or without activation in Salmonella typhimurium strains TA98, TA1535, TA1537, and Escherichia coli strain WP2 uvrA. DETN was negative for all Salmonella tester strains and E. coli up to 5000μg/plate both with and without metabolic activation. The CHO cell chromosome aberration assay was performed using EDDN and DETN at concentrations up to 5000μg/mL. The results indicate that these compounds did not induce structural chromosomal aberrations at all tested concentrations in CHO cells, with or without metabolic activation. EDDN and DETN, when tested in vivo in the CD-1 mouse at doses up to 2000mg/kg, did not induce any significant increase in the number of micronuclei in bone marrow erythrocytes. These studies demonstrate that EDDN is mutagenic in one strain of Salmonella (TA100) but was negative in other strains, for in vitro induction of chromosomal aberrations in CHO cells, and for micronuclei in the in vivo mouse micronucleus assay. DETN was not genotoxic in all in vitro and in vivo tests. These results show the in vitro and in vivo genotoxicity potential of these chemicals.     

In vitro genotoxicity of danthron and its potential mechanism

To ascertain the in vitro genotoxicity of danthron and its potential mechanism of action, we performed an Ames test, a cytokinesis-block micronucleus assay and a comet assay in Balb/c 3T3 cells. The Ames test revealed that danthron was mutagenic only toward Salmonella typhimurium strain TA102 in the presence of an exogenous metabolic activation system (S9 mix). Danthron (25, 50 and 100μg/ml) increased the frequencies of micronuclear cells with or without S9 mix, and the comet length, tail length and Olive tail moment in comet assays without S9 mix in a dose-dependent manner. These results demonstrated the in vitro genotoxicity of danthron and that 3T3 cells are capable of activating danthron. When NADP was replaced by NAD in the S9 mix, danthron remained mutagenic toward strain TA102. The addition of dicoumarol, a DT-diaphorase inhibitor, decreased the number of danthron-induced histidine revertants by 35-39%, indicating that DT-diaphorase is involved in the metabolic activation of danthron in the presence of NADH as an electron donor. In 3T3 cells, increases in reactive oxygen species (ROS) formation and 8-hydroxydeoxyguanosine levels as well as a reduction in GSH levels were induced by danthron in a dose-dependent manner, indicating that oxidative stress may be a major contributing pathway in the genotoxicity of danthron.     

Mutagenic and genotoxic evaluation of bisphenol F diglycidyl ether (BFDGE) in prokaryotic and eukaryotic systems

The epoxy resin bisphenol F diglycidyl ether (BFDGE), was examined for its mutagenicity in prokaryotic assays (Salmonella typhimurium His(-) and Escherichia coli Trp(-) tests) and its genotoxicity in eukaryotic systems (sister chromatid exchange (SCE) and micronucleus tests in human lymphocytes), in the presence or absence of an exogenous metabolizing system (S9 from rat liver). In the prokaryotic tests, the concentrations of BFDGE ranged between 100 and 5000 micro g per plate, and in the eukaryotic assays from 12.5 to 62.5 micro g/ml. The compound is able to induce mutagenic effects in bacterial strains TA100, TA1535, WP2uvrA and IC3327, as revealed by the increase observed in the number of induced revertants. With respect to the genotoxicity assays, BFDGE induces an increase in the frequency of sister chromatid exchanges and micronuclei in human peripheral blood lymphocytes.     

Genotoxicity tests with 6-acetyl-1,1,2,4,4,7-hexamethyltetraline and 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-gamma-2-benzopyr an

6-Acetyl-1,1,2,4,4,7-hexamethyltetraline (AHTN) and 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-gamma-2-ben zopyran (HHCB), synthetic fragrance ingredients, were evaluated for potential genotoxicity in a battery of short-term tests. Salmonella typhimurium/Escherichia coli plate incorporation and liquid preincubation assays were conducted on AHTN using tester strains TA97, TA98, TA100, TA102, TA1535, TA1537 and WP2 uvrA +/- S9 activation at doses from 8 to 5000 micrograms/plate. The plate incorporation mutagenicity assay was conducted on HHCB using tester strains TA98, TA100, TA1535, TA1537, TA1538 and WP2 uvrA +/- S9 activation at doses from 10 to 5000 micrograms/plate. An in vitro cytogenetics assay in Chinese hamster ovary (CHO) cells was conducted with AHTN and HHCB at three concentrations each with +/- S9 activation. In the non-activated study, the exposure/harvest periods were 4/20-, 20/20- and 44/44-h. In the S9 activated study, the exposure/harvest periods were 4/20- and 4/44-h. In vitro unscheduled DNA synthesis (UDS) assays were conducted in primary rat hepatocytes at concentrations between 0.15 and 50 micrograms/ml for AHTN and HHCB. In vivo mouse micronucleus assays were conducted with high doses of 1600 mg AHTN/kg and of 1500 mg HHCB/kg in corn oil. No positive responses were observed in any of the tests with HHCB. With AHTN, no positive responses were observed except for cells with structural aberrations in the in vitro cytogenetics assay in CHO cells with S9 activation at the treatment/harvest time of 4/20 h. In initial studies with AHTN, the high dose of 7.8 micrograms/ml showed 0.5% aberrant cells, with the mitotic index at 41% relative to vehicle control and cell growth inhibition in the range of 25-50%. Thus the genotoxicity findings with AHTN were limited to this one positive response; all other genotoxicity tests with AHTN were considered as negative. In particular, the negative finding in the in vivo assay supports AHTN as not likely to be mutagenic in mammalian systems. These considerations, along with other negative published data, lead to the conclusion that both AHTN and HHCB do not have significant potential to act as genotoxic carcinogens.     

Clastogenic and mutagenic effects of bisphenol A: an endocrine disruptor

Bisphenol A (BPA) is a well-known endocrine disruptor (ED) which represents a major toxicological and public health concern due to its widespread exposure to humans. BPA has been reported to induce DNA adduct and aneuploidy in rodents. Recent studies in humans depicted its association with recurrent miscarriages and male infertility due to sperm DNA damage indicating that BPA might have genotoxic activity. Hence, the present study was designed to determine genotoxic and mutagenic effects of BPA using in-vivo and in-vitro assays. The adult male and female rats were orally administered with various doses of BPA (2.4 μg, 10 μg, 5mg and 50mg/kgbw) once a day for six consecutive days. Animals were sacrificed, bone marrow and blood samples were collected and subjected to series of genotoxicity assay such as micronucleus, chromosome aberration and single cell gel electrophoresis (SCGE) assay respectively. Mutagenicity was determined using tester strains of Salmonella typhimurium (TA 98, TA 100 and TA 102) in the presence and absence of metabolically active microsomal fractions (S9). Further, we estimated the levels of 8-hydroxydeoxyguanosine, lipid per-oxidation and glutathione activity to decipher the potential genotoxic mechanism of BPA. We observed that BPA exposure caused a significant increase in the frequency of micronucleus (MN) in polychromatic erythrocytes (PCEs), structural chromosome aberrations in bone marrow cells and DNA damage in blood lymphocytes. These effects were observed at various doses tested except 2.4 μg compared to vehicle control. We did not observe the mutagenic response in any of the tester strains tested at different concentrations of BPA. We found an increase in the level of 8-hydroxydeoxyguanosine in the plasma and increase in lipid per-oxidation and decrease in glutathione activity in liver of rats respectively which were exposed to BPA. In conclusion, the data obtained clearly documents that BPA is not mutagenic but exhibit genotoxic activity and oxidative stress could be one of the mechanisms leading to genetic toxicity.     

The Salmonella mutagenicity of industrial, surface and ground water samples of Aligarh region of India

The genotoxicity of three water bodies, viz. industrial waste water of Aligarh city, ground water pumped out from the industrial area of Aligarh, and river water of Yamuna, downstream of Agra, was carried out by means of Ames plate incorporation test and the Ames fluctuation test. All the test samples were significantly mutagenic in both the testing systems. The ground water and river water samples were subjected to XAD concentration prior to the mutagenicity/genotoxicity testing, while the industrial waste water was used directly. Whereas TA98, TA102 and TA104 strains have been found to be maximally sensitive in the Ames plate incorporation assay conducted for various water samples, TA98 and TA100 strains were the most responsive strains in the Ames fluctuation test. The apparent disparity in the sensitivity patterns of various Ames strains by plate incorporation and fluctuation assays could be attributed to a large extent to the different conventional ways of interpretation of the data in these systems.     

The mutagenic hazards of aquatic sediments: a review

Sediments are the sink for particle-sorbed contaminants in aquatic systems and can serve as a reservoir of toxic contaminants that continually threaten the health and viability of aquatic biota. This work is a comprehensive review of published studies that investigated the genotoxicity of sediments in rivers, lakes and marine habitats. The Salmonella mutagenicity test is the most frequently used assay and accounts for 41.1% of the available data. The Salmonella data revealed mutagenic potency values for sediment extracts (in revertants per gram dry weight) that spans over seven orders of magnitude from not detectable to highly potent (10(5) rev/g). Analyses of the Salmonella data (n=510) showed significant differences between rural, urban/industrial, and heavily contaminated (e.g., dump) sites assessed using TA98 and TA100 with S9 activation. Additional analyses showed a significant positive correlation between Salmonella mutagenic potency (TA98 and TA100 with S9) and PAH contamination (r2=0.19-0.68). The second and third most commonly used assays for the analysis of sediments and sediment extracts are the SOS Chromotest (9.2%) and the Mutatox assays (7.8%), respectively. These assays are frequently used for rapid initial screening of collected samples. A variety of other in vitro endpoints employing cultured fish and mammalian cells have been used to investigate sediment genotoxic activity. Endpoints investigated include sister chromatid exchange frequency, micronucleus frequency, chromosome aberration frequency, gene mutation at tk and hprt loci, unscheduled DNA synthesis, DNA adduct frequency, and DNA strand break frequency. More complex in vivo assays have documented a wide range of effects including neoplasms and preneoplastic lesions in fish and invertebrate exposed ex situ. Although costly and time consuming, these assays have provided definitive evidence linking sediment contamination and a variety of genotoxic and carcinogenic effects observed in situ.     

Evaluation of the genotoxic potential of the natural neurotoxin Tetrodotoxin (TTX) in a battery of in vitro and in vivo genotoxicity assays

The genotoxic potential of the natural neurotoxin Tetrodotoxin (TTX) was evaluated in a battery of in vitro and in vivo genotoxicity assays. These comprised a bacterial reverse-mutation assay (Ames test), an in vitro human lymphocyte chromosome-aberration assay, an in vivo mouse bone-marrow micronucleus assay and an in vivo rat-liver UDS assay. Maximum test concentrations in in vitro assays were determined by the TTX limit of solubility in the formulation vehicle (0.02% acetic acid solution). In the Ames test, TTX was tested at concentrations of up to 200 microg/plate. In the chromosome-aberration assay human lymphocytes were exposed to TTX at concentrations of up to 50 microg/ml for 3 and 20 h in the absence of S9, and for 3h in the presence of S9. For the in vivo assays, maximum tested dose levels were determined by the acute lethal toxicity of TTX after subcutaneous administration. In the mouse micronucleus assay TTX dose levels of 2, 4 and 8 microg/kg were administered to male and female animals, and bone-marrow samples taken 24 and 48 h (high-dose animals only) after administration. In the UDS assay, male rats were given TTX on two occasions with a 14-h interval at dose levels of 2.4 and 8 microg/kg, the last dose being administered 2h before liver perfusion and hepatocyte culturing. Relevant vehicle and positive control cultures and animals were included in all assays. TTX was clearly shown to lack in vitro or in vivo genotoxic activity in the assays conducted in this study. The results suggest that administration of TTX as a therapeutic analgesic agent would not pose a genotoxic risk to patients.     

In vitro short-term test evaluation of catecholestrogens genotoxicity

Estrogens are indicated as being the most important etiological factors for the development and progression of breast cancer. The implication of estrogen in breast cancer has been associated mostly with the estrogen receptors that mediate cell proliferation. Evidence also exists to support the hypothesis of a direct role of estrogens as tumor initiators. However, the role of estrogen genotoxicity in breast cancer is still questionable.

In this study the genotoxic activity of catecholestrogens and 16-hydroxy estrone has been investigated by performing Salmonella strain TA98 and TA100 Ames tests, sister chromatide exchange assays (SCE) and micronucleus assays on human peripheral lymphocytes (CBMN and ARA/CBMN). We found a lack of positive results with micronucleus assays, except for 2-hydroxy estradiol (2-OHE₂), which shows a peculiar “bell shaped” trend of micronucleus number versus concentrations. SCE assay suggests weak genotoxic activity of all tested catechol metabolites, except 4-hydroxy estrone (4-OHE₁), which also showed negative results by ARA/CBMN.

In this open debate, our results support the hypothesis of a weak genotoxicity, not correlated with the carcinogenetic potential of estrogens.     

Absence of genotoxic activity of penbutolol in bacterial and mammalian cell screening systems

The genotoxic potential of the beta-adrenergic blocker penbutolol was assessed using the Ames and HGPRT tests, unscheduled DNA synthesis (UDS) and alkaline elution assays. In the Ames test, penbutolol was tested for cytotoxicity and genotoxic activity in concentration ranges of 0.8-500 micrograms/plate and 0.1-125 micrograms/ml in the HGPRT, UDS and alkaline elution assays. In the Ames test penbutolol showed significant toxicity above 500 micrograms/plate. In the mammalian cells (V79) used for the HGPRT test and A459 cells used for alkaline elution and UDS assays, penbutolol was cytotoxic at concentrations above 30 micrograms/ml. In another series of experiments, male Wistar rats were treated i.p. with penbutolol (1, 10 and 100 mg/kg) and after 2 h liver nuclei were isolated and formation of single DNA-strand breaks was measured. The results of the present study demonstrate the absence of genotoxic activity of penbutolol in the 5 strains of Salmonella typhimurium (TA98, TA100, TA1535, TA1537 and TA1538) and in the strain of Escherichia coli WP2 uvrA in the presence or absence of metabolic activation. In V79 cells, penbutolol showed no mutagenic effects at the HGPRT locus in the presence or absence of metabolic activation. Additionally, no significant incorporation of [3H]thymidine into the DNA in the UDS test or formation of DNA-strand breaks in the alkaline elution assay was detected in the non-toxic concentration range of penbutolol with or without metabolic activation. Furthermore, penbutolol did not cause DNA damage in liver nuclei isolated from penbutolol-treated rats.     

Comparative chemical analysis,mutagenicity, and genotoxicity of Petroleum refinery wastewater and its contaminated river using prokaryotic and eukaryotic assays

Concern on the toxicity of final wastewater generated by the petroleum refining industry has increased in recent years due to the potential health threats associated with their release into the waterways. This study determined the mutagenic and genotoxic potential of petroleum refinery wastewater and a receiving river using the Ames fluctuation test on Salmonella typhimurium strains TA100 and TA98, SOS chromotest on Escherichia coli PQ37, and piscine peripheral micronucleus (MN) assay. Analyses of the physicochemical parameters, heavy metal, and organic contents of the samples were also performed. Ames test result showed that the two tested samples were mutagenic with TA100 strain as the more responsive strain for both the refinery wastewater and the river sample in terms of the calculated mutagenic index. A similar result was obtained in the SOS chromotest; however, the E. coli PQ37 system recorded a slightly higher sensitivity for detecting genotoxins than the Salmonella assay in the two samples. MN data showed induction of a concentration-dependent significant (p < 0.05) increase in the frequency of MN by both samples when compared with the negative control. Generally, the refinery wastewater induced the highest mutagenicity and genotoxicity compared to the river sample in the three assays used. Haemoglobin, platelets, red blood cells, mean corpuscular volume, total white blood cells, heterophils, haematocrit, and eosinophils reduced significantly with increased lymphocytes, basophils, mean corpuscular haemoglobin, and mean corpuscular haemoglobin concentration in fishes exposed to both samples. Total petroleum hydrocarbon, benzene, toluene, phenol index, polycyclic aromatic hydrocarbons, cadmium, mercury, nickel, lead, and vanadium contents analysed in the samples were believed to be responsible for the observed genotoxicity and mutagenicity. The findings of this study revealed that petroleum refinery wastewater is a potential mutagenic and genotoxic risk to the environment.

     

Evaluation of the genotoxic potential of the natural neurotoxin Tetrodotoxin (TTX) in a battery of in vitro and in vivo genotoxicity assays

The genotoxic potential of the natural neurotoxin Tetrodotoxin (TTX) was evaluated in a battery of in vitro and in vivo genotoxicity assays. These comprised a bacterial reverse-mutation assay (Ames test), an in vitro human lymphocyte chromosome-aberration assay, an in vivo mouse bone-marrow micronucleus assay and an in vivo rat-liver UDS assay.Maximum test concentrations in in vitro assays were determined by the TTX limit of solubility in the formulation vehicle (0.02% acetic acid solution). In the Ames test, TTX was tested at concentrations of up to 200 μg/plate. In the chromosome-aberration assay human lymphocytes were exposed to TTX at concentrations of up to 50 μg/ml for 3 and 20 h in the absence of S9, and for 3 h in the presence of S9. For the in vivo assays, maximum tested dose levels were determined by the acute lethal toxicity of TTX after subcutaneous administration. In the mouse micronucleus assay TTX dose levels of 2, 4 and 8 μg/kg were administered to male and female animals, and bone-marrow samples taken 24 and 48 h (high-dose animals only) after administration. In the UDS assay, male rats were given TTX on two occasions with a 14-h interval at dose levels of 2.4 and 8 μg/kg, the last dose being administered 2 h before liver perfusion and hepatocyte culturing. Relevant vehicle and positive control cultures and animals were included in all assays.TTX was clearly shown to lack in vitro or in vivo genotoxic activity in the assays conducted in this study. The results suggest that administration of TTX as a therapeutic analgesic agent would not pose a genotoxic risk to patients.     

Ethylene thiourea (ETU). A review of the genetic toxicity studies

Ethylene thiourea (ETU) is a common contaminant, metabolite and degradation product of the fungicide class of ethylene bisdithiocarbamates (EBDCs); as such, they present possible exposure and toxicological concerns to exposed individuals. ETU has been assayed in many different tests to assess genotoxicity activity. While a great number of negative results are found in the data base, there is evidence that demonstrates ETU is capable of inducing genotoxic endpoints. These include responses for gene mutations (e.g. Salmonella), structural chromosomal alterations (e.g. aberrations in cultured mammalian cells as well as a dominant lethal assay) and other genotoxic effects (e.g. bacterial rec assay and several yeast assays).It is important to consider the magnitude of the positive responses as well as the concentrations/doses used when assessing the genotoxicity of ETU. While ETU induces a variety of genotoxic endpoints, it does not appear to be a potent genotoxic agent. For example, it is a weak bacterial mutagen in the Salmonella assay without activation in strain TA1535 at concentrations generally above 1000 μg/plate. Weak genotoxic activity of this sort is usually observed in most of the assays with positive results. Since ETU does not appear very potent and is not extremely toxic to test cells and organisms, it is not surprising to find that ETU does not produce consistent effects in many of the assays reviewed. Consequently, in many instances, mixed results for the same assay type are reported by different investigators, but as reviewed herein, these results may be dependent upon the test conditions in each individual laboratory. A primary shortcoming with many of the reported negative results is that the concentrations or doses used are not high enough for an adequate test for ETU activity. There are also problems with many of the negative assays generally in protocol or reporting, particularly with the in vivo studies (e.g. inappropriate sample number and/or sampling times; inadequate top dose employed).Overall, while ETU does not appear to be a potent genotoxic agent, it is capable of producing genotoxic effects (e.g. gene mutations, structural chromosomal aberrations). This provides a basis for weak genotoxic activity by ETU. Furthermore, based on a suggestive dominant lethal positive result, there may be a concern for heritable effects. Due to the many problems with the conduct and assessment of the in vivo assays, it is worth repeating in vivo     

Mutagenic and genotoxic effects of Anilofos with micronucleus,chromosome aberrations,sister chromatid exchanges and Ames test

We aimed to evaluate the mutagenic effect of Anilofos, organophosphate pesticide, by using Ames/Salmonella/microsome test. Its cytotoxic and genotoxic effects were also determined by chromosome aberration (CA), sister chromatid exchange (SCE) and micronucleus (MN) test in human peripheral blood lymphocytes. In the Ames test, five different concentrations of Anilofos were examined on TA97, TA98, TA100 and TA102 strains in the absence and presence of S9 fraction. According to the results all concentrations of this pesticide have not shown any mutagenic activity on TA97, TA100 and TA102 strains in the absence and presence of S9 fraction. But, 10, 100 and 1000 µg/plate concentrations of Anilofos were determined to be mutagenic on TA98 strain without S9 fraction. Lymphocytes were treated with various concentrations (25, 50, 100 and 200 µg/ml) of Anilofos for 24 and 48 h. The results of the assays showed that Anilofos did not induce SCE frequency, replication index and MN formation at all concentrations for both treatment periods. Anilofos significantly increased CA frequency at 100 and 200 µg/ml concentrations at 24 h treatment periods and at 50, 100 and 200 µg/ml concentrations in 48 h treatment periods. Additionally, it was determined that this pesticide decreased mitotic index and nuclear division index significantly. It was concluded that Anilofos has genotoxic and cytotoxic effects in human peripheral lymphocytes.     

Bacterial reversion assay and micronucleus test carried out on hydrogenated glucose syrups 'Malti-Towa' (powder) and maltitol crystal

Two preparations of maltitol (4-O-alpha-D-glucopyranosyl-D-sorbitol), hydrogenated glucose syrups and maltitol crystal, were examined for genotoxic potential by a battery of short-term tests. In the bacterial reversion assay, maltitol induced no detectable revertants in any of the tester strains, Salmonella typhimurium TA98, TA100, TA1535, TA1537, TA1538, or Escherichia coli WP2/pKM101 at doses of 0.5-50 mg per plate with and without rat liver S9 mix. In the micronucleus test, no significant increase in the frequency of micronucleated erythrocytes was observed in bone marrow of mice after administration of the two preparations at 3.75-30 g per kg by gastric intubation.     

Mutagenicity study of fried sausages in Salmonella, Drosophila and mammalian cells in vitro and in vivo

The basic extract of pan-fried sausages was studied for mutagenic potential in seven test systems. Mutagenic activity was high in the standard Ames assay in the Salmonella typhimurium strains TA1538 and TA98 in presence of S9 mix. In vivo, in the intrasanguine host-mediated assay with strain TA98 on Aroclor-pretreated mice, the mutagenic activity of the extract was low. A borderline activity was seen in the SCE assay in vitro with V79 Chinese hamster cells in presence of S9 mix. No significant mutagenic action was found in the gene-mutation assay for thioguanine resistance with V79 cells, the Drosophila sex-linked recessive lethal test, the micronucleus test and the mammalian spot test.     

Genotoxicity of drinking water from three Korean cities

Organic content of drinking tap water from Seoul, Taejon, and Suwon was extracted with an XAD-2 resin column and organic solvents. Four doses of the extract equivalent to 4, 2, 1, and 0.5 l water were tested for mutagenicity in Salmonella typhimurium strains TA98 and TA100 in the presence and absence of S9 mix. The organic extracts of the water from all three cities were mutagenic in TA 98 without S9 mix and in TA 100 with and without S9 mix. The highest number of revertants per plate was found in the absence of S9 mix. Three doses of the extract (equivalent to 22, 11, and 3.7 l water) were also tested in the bone marrow micronucleus test using BDF1 mice. At the highest dose, a significant increase of the micronucleus frequency was observed. The time required to be on the effect, however, varied with the source of the water. Our results indicate that the drinking tap waters from the three cities were genotoxic clearly in the bacterial test and also in the in vivo assay with mice. As we found no genotoxicity of the source water as seen in a previous study, it is likely that the chlorination process leads to the genotoxicity of the tap water.     

Assessment of the mutagenic potential of arecoline in gpt delta transgenic mice

Until recently, knowledge about the genotoxicity of roxarsone in vitro or in vivo was limited. This study assessed the genotoxicity of roxarsone in an in vitro system. Roxarsone was tested for potential genotoxicity on V79 cells by a Comet assay and a micronucleus (MN) test, exposing the cells to roxarsone (1-500 μM) and to sodium arsenite (NaAsO?, 20 μM) solutions for 3-48 h. Roxarsone was found to be cytotoxic when assessed with a commercial cell counting kit (CCK-8) used to evaluate cell viability, and moderately genotoxic in the Comet assay and micronucleus test used to assess DNA damage. The Comet metrics (percentages TDNA, TL, TM) increased significantly in a time- and concentration-dependent manner in roxarsone-treated samples compared with PBS controls (P<0.05), while the data from samples treated with 20 μM NaAsO? were comparable to those from 500 μM roxarsone-treated samples. The MN frequency of V79 cells treated with roxarsone was higher than that in the negative control but lower than the frequency in cells treated with 20 μM NaAsO?. A dose- and time-dependent response in MN induction was observed at 10, 50, 100 and 500 μM doses of roxarsone after 12-48 h exposure time. The DNA damage in V79 cells treated with 500 μM roxarsone was similar to cells exposed to 20 μM NaAsO?. The uptake of cells was correlated with the DNA damage caused by roxarsone. This investigation depicts the genotoxic potentials of roxarsone to V79 cells, which could lead to further advanced studies on the genotoxicity of roxarsone.     

An assessment of the genotoxicity of 2-hydroxy-1,4-naphthoquinone,the natural dye ingredient of Henna

2-Hydroxy-1,4-naphthoquinone (HNQ; Lawsone; CAS 83-72-7) is the principal natural dye ingredient contained in the leaves of Henna (Lawsonia inermis). Published genotoxicity studies on HNQ suggested it was a weak bacterial mutagen for Salmonella typhimurium strain TA98 or was more clearly mutagenic for strain TA 2637, both in the presence of metabolic activation. HNQ was unable to induce sex-linked recessive lethal mutations in Drosophila melanogaster. However, a small increase in micronucleus frequency was reported in the bone marrow of mice at a single mid-range dose level, 24h after intraperitoneal injection. In view of the wide use of Henna hair dyes it was deemed necessary to conduct a thorough investigation, under Good Laboratory Practice conditions, of the genotoxicity of HNQ. HNQ was non-mutagenic in bacterial (Ames test) or mammalian (V79 hprt) assays. It was borderline positive in a mouse lymphoma tk mutation assay and a chromosome aberration test (CHO cells), results that may reflect a similar clastogenic mechanism. Negative in vivo genotoxicity results were noted in the rat hepatocyte in vivo/in vitro UDS test, in peripheral lymphocytes (chromosome aberrations) of rats receiving repeated oral doses of HNQ at the MTD for 28 days, and in mouse and hamster bone marrow chromosome aberration tests. However small, but statistically significant increases in the incidence of bone marrow micronuclei were observed in two out of five tests at 72 h after dosing, but not at 24 or 48 h. There was evidence of haematotoxicity at 72 h, which may have been enhanced by the vehicle (DMSO) used in the positive tests. As erythropoiesis and administration of haematotoxic agents are known to induce small increases in the frequency of bone marrow micronuclei, typically at delayed sampling times, the data suggest that the positive 72 h response produced by HNQ is consistent with stimulation of haematopoiesis subsequent to haematological toxicity of HNQ, and not due to a DNA-reactive mechanism. Overall, the weight of evidence suggests that Henna and HNQ pose no genotoxic risk to the consumer.