Genotoxicity Assessment of HM10620 Containing Recombinant Human Interferon-α

HM10620 is a recombinant human interferon-α (rhIFN-α) linked to immunoglobulin via N-terminal–specific non-peptidyl polyethylene glycol linker to improve the in vivo stability of interferon. Potential genotoxic effects of HM10620 in three short-term mutagenicity assays were investigated, which included the Ames assay, in vitro chromosomal aberration assay, and the in vivo micronucleus assay. HM10620 did not cause any mutation in the Ames assay tested using five tester strains at six concentrations of 6.25, 12.5, 25, 50, 100, and 200 μg/plate. To assess clastogenic effect, the in vitro chromosomal aberration assay and the in vivo micronucleus assay were performed using Chinese hamster lung cells and male ICR mice, respectively. Chromosomal aberration was not induced at the concentrations of 10, 20, and 40 μg/mL. Also, there was no difference in the incidence of micronucleated polychromatic erythrocytes at doses of 10, 20, and 40 mg/kg in male mice compared with the vehicle control group. Therefore, based on the results obtained from the three studies, it is concluded that HM10620 is not a mutagenic agent in bacterial cells and causes no chromosomal damage in mammalian cells both in vitro and in vivo.     

Mutagenicity and clastogenicity evaluation of tacrine by Ames and micronucleus assays

Tacrine was evaluated for its mutagenic and clastogenic activities using the Ames bacterial reverse-mutation assay and the rodent bone marrow micronucleus assay. Tacrine was tested for mutagenic potential at six different concentrations, with 1,250 µg/plate as the highest concentration, followed by five lower concentrations with 2-fold spacing. In clastogenic evaluation, tacrine was administered orally to Wistar rats for 2 days at 5, 10, and 20?mg/kg body weights to assess micronucleus induction in bone marrow erythrocytes. In the Ames assay, tacrine showed nonmutagenicity in four tester strains of Salmonella typhimurium viz. TA98, TA100, TA102, and TA1535, but it was found to be mutagenic in the TA1537 tester strain, both in the presence and absence of a metabolic activation system. Tacrine was found to be nonclastogenic on bone marrow cells of rats at all doses tested and was found to be mutagenic in only the TA1537 strain of Salmonella.     

毛蚶提取物的遗传毒性试验研究

目的 评价毛蚶提取物的遗传毒性,为评价其安全性提供毒理学依据。方法 选用体外细菌回复突变(Ames)试验、中国仓鼠肺细胞(CHL)体外染色体畸变试验、小鼠骨髓嗜多染红细胞微核试验,进行毛蚶提取物的遗传毒性研究。Ames试验设5000.0、2500.0、1250.0、625.0、312.5 μg/皿5个剂量;体外CHL细胞染色体畸变试验,设立5.00、2.50、1.25 mg/mL 3个剂量,毛蚶提取物与CHL细胞分别接触6、24 h;小鼠骨髓微核试验,设立5000、2500、1250 mg/kg 3个剂量,给药1次。结果 Ames试验,毛蚶提取物在加与不加S9时各剂量组回变菌落数均未超过自发回变菌落数的2倍,亦无剂量相关性,结果为阴性;CHL染色体畸变试验,毛蚶提取物代谢活化组和非代谢活化组的染色体畸变率均低于5%,染色体畸变试验结果为阴性。小鼠骨髓微核试验,各剂量组的微核率与阴性对照组比较,差异不显著,结果为阴性。结论 在本试验条件下,毛蚶提取物未见潜在的遗传毒性。     

Evaluation of the genotoxic potential of single-wall carbon nanotubes by using a battery of in vitro and in vivo genotoxicity assays

The genotoxic potential of a high purity sample of single-wall carbon nanotubes (SWCNTs) was evaluated using a battery of in vitro and in vivo genotoxicity assays. These comprised a bacterial reverse mutation test (Ames test), an in vitro chromosomal aberration test, and an in vivo mouse bone marrow micronucleus test. The SWCNTs exerted no genotoxicity in Salmonella typhimurium TA97, TA98, TA100, and TA1535, or in Escherichia coli WP2 uvrA/pKM101, whether in the absence or presence of metabolic activation and at concentrations of 12.5–500 μg/plate. In the chromosomal aberration test, at 300–1000 μg/mL, the SWCNTs did not increase the number of structural or numerical chromosomal aberrations, whether the test was conducted with or without metabolic activation. In the in vivo bone marrow micronucleus test, doses of 60 mg/kg and 200 mg/kg SWCNTs did not affect the proportions of immature and total erythrocytes, nor did it increase the number of micronuclei in the immature erythrocytes of mice. The results of these studies show that the high purity and well-dispersed sample of SWCNTs are not genotoxic under the conditions of the in vitro bacterial reverse mutation assay, chromosomal aberration assay, or in vivo bone marrow micronucleus test, and thus appear not to pose a genotoxic risk to human health in vivo.     

Genotoxicity studies on HM10760A,recombinant human erythropoietin conjugated to globin fragment

HM10760A is a recombinant human erythropoietin chemically conjugated to the N-terminus of human immunoglobulin Fc fragment through a polyethylene glycol linker. HM10760A was shown to have a relatively long half-life, compared with unconjugated recombinant erythropoietin. In this study, the genotoxicity of HM10760A was investigated by using a test battery of three different methods. In the Ames assay, five strains (TA100, TA1535, TA98, TA1537, and Escherichia coli WP2 uvrA) were tested at six concentrations of 3.13, 6.25, 12.5, 25, 50, and 100?μg/plate. HM10760A did not increase the number of revertant colonies in any tester strains with and without metabolic activation by rat-liver S9 mix. Subsequently, in vitro chromosomal aberration test, using Chinese hamster lung cells, were conducted at the concentrations of 25, 50, and 100?μg/mL. HM10760A did not induce chromosomal aberrations either in the short-period (6 hours) test with or without rat-liver S9 mix or in the continuous-treatment (24 hours) test. In the in vivo bone marrow micronucleus assay using the male ICR (imprinting control region) mouse, HM10760A was subcutaneously administered twice at 24-hour intervals at doses of 0, 150, 300, and 600?μg/kg. HM10760A produced a slight, but statistically significant, increase in the frequency of micronucleated polychromatic erythrocytes at 600?μg/kg. However, no biological significance was assumed, because this value was within the historical control range. From these findings obtained from the genotoxicity assays performed in this study, it appears unlikely that HM10760A acts as a genotoxic agent in vitro and in vivo.     

赤苷脉通注射液的致突变研究

目的探讨中药制剂赤苷脉通注射液的致突变性。方法采用鼠伤寒沙门氏组氨酸营养缺陷型菌株回复突变实验(Ames实验)、中国仓鼠肺成纤维细胞(CHL)染色体畸变实验和小鼠骨髓微核实验来检测赤苷脉通注射液的致突变作用。结果 Ames实验中,赤苷脉通注射液在312.5～5 000μg.皿-1剂量范围内,无论加或不加S9,鼠伤寒沙门氏菌组氨酸缺陷型TA97,TA98,TA100,TA102和TA1535 5株菌的回复突变菌落数均未出现剂量依赖性的增加;染色体畸变实验中,非活化条件或代谢活化条件下,药物质量浓度为1 200,600和300μg.mL-1时,细胞的染色体畸变率均未出现剂量依赖性增加;微核实验中,在1 150,575和287.5mg.kg-1剂量组中均未见骨髓中含微核的嗜多染红细胞数增加。结论在该实验室条件下,Ames实验、CHL细胞染色体畸变实验和小鼠骨髓微核实验结果均为阴性,即中药制剂赤苷脉通注射液无潜在的遗传毒性。     

Evaluation of genotoxicity of nitrile fragrance ingredients using in vitro and in vivo assays

Genotoxicity studies were conducted on a group of 8 fragrance ingredients that belong to the nitrile family. These nitriles are widely used in consumer products however there is very limited data in the literature regarding the genotoxicity of these nitriles. The 8 nitriles were assessed for genotoxicity using an Ames test, in vitro chromosome aberration test or in vitro micronucleus test. The positive results observed in the in vitro tests were further investigated using an in vivo micronucleus test. The results from these different tests were compared and these 8 nitriles are not considered to be genotoxic. Dodecanitrile and 2,2,3-trimethylcyclopent-3-enylacetonitrile were negative in the in vitro chromosome aberration test and in vitro micronucleus test, respectively. While citronellyl nitrile, 3-methyl-5-phenylpentanenitrile, cinnamyl nitrile, and 3-methyl-5-phenylpent-2-enenitrile revealed positive results in the in vitro tests, but confirmatory in vivo tests determined these nitriles to be negative in the in vivo micronucleus assay. The remaining two nitriles (benzonitrile and α-cyclohexylidene benzeneacetonitrile) were negative in the in vivo micronucleus test. This study aims to evaluate the genotoxicity potential of these nitriles as well as enrich the literature with genotoxicity data on fragrance ingredients.     

Genotoxicity study of bojungchisup-tang, an oriental herbal decoction-in vitro chromosome aberration assay in Chinese hamster lung cells andin vivo supravital-staining micronucleus assay with mouse peripheral reticulocytes

The toxicity evaluation of oriental herbal drugs is of great concern at present. Bojungchisuptang (BCST, in Korean), a decocted medicine of oriental herbal mixture, is now well used in clinic at oriental hospitals for the treatment of edema of several diseases in practice. However, the toxicity of the oriental herbal decocted medicines such as genetic toxicity is not well defined until now. In this respect, to clarify the genetic toxicity of BCST,in vitro chromosome aberration assay with Chinese hamster lung (CHL) fibroblasts andin vivo supravital micronucleus assay with mouse peripheral reticulocytes were performed in this study. In the chromosome aberration assay, we used 5,000 μg/ml BCST as maximum concentration because no remarkable cytotoxicity in CHL cells was observed both in the presence and absence of S-9 metabolic activation system. No statistical significant differences of chromosome aberrations were observed in CHL cells treated with 5,000, 2,500 and 1,250 μg/ml BCST for 6 hour both in the presence and absence of S-9 metabolic activation. However, very weak positive result (6.5∼8.0% aberration) of BCST was obtained in the absence of S-9 metabolic activation system at 5,000 μg/ml BCST when treated for 24 hour, i.e. 1.5 normal cell cycle time. And also,in vivo clastogenicity of BCST was studied by acridine orange-supravital staining micronucleus assay using mouse peripheral reticulocytes. We used 2,000 mg/kg as the highest oral dose in this micronucleus assay because no acute oral toxicity of BCST was observed in mice. The optimum induction time of micronucleated reticulocytes (MNRETs) was determined as 36 hours after oral administration of 2,000 mg/kg BCST. No significant differences of MNRETs between control and BCST treatment groups were observedin vivo micronucleus assay. From these results, BCST revealed very weak positive result in chromosome aberration assayin vitro with CHL cells and no clastogenicity in micronucleus assayin vivo.     

Assessment of combinations of antiandrogenic compounds vinclozolin and flutamide in a yeast based reporter assay

Glycyrrhiza glabra Linn. (licorice) is widespread throughout the Mediterranean region and certain areas of Asia. Historically, the dried rhizome and root of the plant were used by the Chinese, Egyptian, Greek, Indian, and Roman civilizations as expectorant and carminative. In the modern medicinal system, licorice is used to treat liver ailments, dyspepsia, bronchitis, rheumatoid arthritis etc. Despite the extensive pharmacological applications, the genotoxic potential of G. glabra extract (GutGard™) has not been evaluated. Hence, this study was conducted to investigate the genotoxic potential of GutGard™ using battery of in vitro test systems: bacterial reverse mutation test (Ames II™), chromosome aberration (CA) and micronucleus (MN) tests. GutGard™ did not show significant increase in number of revertant colonies in Salmonella typhimurium strains (TA98 and TAMix) with/without S9 fraction. In CA and MN studies, GutGard™ did not show clastogenic effect at 4 and 18 h treatments with and without S9 fraction. Results indicated that GutGard™ is not mutagenic in a battery of genotoxicity tests.     

Mutagenicity and clastogenicity evaluation of tacrine by Ames and micronucleus assays

Tacrine was evaluated for its mutagenic and clastogenic activities using the Ames bacterial reverse-mutation assay and the rodent bone marrow micronucleus assay. Tacrine was tested for mutagenic potential at six different concentrations, with 1,250 μg/plate as the highest concentration, followed by five lower concentrations with 2-fold spacing. In clastogenic evaluation, tacrine was administered orally to Wistar rats for 2 days at 5, 10, and 20?mg/kg body weights to assess micronucleus induction in bone marrow erythrocytes. In the Ames assay, tacrine showed nonmutagenicity in four tester strains of Salmonella typhimurium viz. TA98, TA100, TA102, and TA1535, but it was found to be mutagenic in the TA1537 tester strain, both in the presence and absence of a metabolic activation system. Tacrine was found to be nonclastogenic on bone marrow cells of rats at all doses tested and was found to be mutagenic in only the TA1537 strain of Salmonella.     

Mutagenicity and clastogenicity evaluation of metaphenoxy benzyl chloride by ames and micronucleus assays

Metaphenoxy Benzyl Chloride (3-PBC; CAS # 53874-66-1) is a commonly used intermediate in organic synthesis and is a widely used chemical building block. There is likelihood of human contact with 3-PBC in the process of organic or pesticide synthesis and even through as impurity in the product. Further, this chemical has been reported to be found in water reservoirs causing a threat to aqueous flaura and fauna. Genotoxic alert has been suspected for the chemical 3-PBC based on its structure hence, the impetus of present work was to assess the mutagenic potential of 3-PBC using Ames bacterial reverse-mutation assay and in vitro micronucleus assay. 3-PBC was tested for mutagenic potential at six different concentrations, with 0.05 (without metabolic activation) and 0.50 (with metabolic activation) µL/plate as the highest concentrations, followed by five lower concentrations with 2-fold spacing. In clastogenic evaluation, 3-PBC was tested at concentrations ranged from 0.31 to 4.88?µL/mL to assess micronucleus induction in mammalian cells viz. Chinese Hamster Ovarian-K1 cells (CHO-K1 cells). In the Ames assay, 3-PBC did not show mutagenicity in all five tester strains of Salmonella typhimurium viz. TA98, TA100, TA102, TA1535 and TA1537 both in the presence and absence of a metabolic activation system and found to be nonclastogenic when evaluated in “CHO-K1 cells”.     

Mutagenic, cytotoxic, and genotoxic properties of tobacco smoke produced by cigarillos available on the Canadian market

Cigarillos (aka little cigars) have been increasing in popularity unlike cigarettes; but relatively little is known about the toxicology of the mainstream smoke (MSS) from such products. Therefore, the objective of this work was to compare the toxicological properties of the MSS (Health Canada Intensive smoking conditions) from a range of cigarillo products with the toxicological properties of MSS of cigarettes. Three in vitro assays were used to evaluate the toxicities of the MSS total particulate matter (TPM): (1) mutagenicity using Ames assay with Salmonella strains TA98 and TA100 with S9 metabolic activation (+S9); (2) cytotoxicity using the Neutral Red Uptake (NRU) assay with CHO (Chinese Hamster Ovary) cells; and (3) genotoxicity using the micronucleus assay with CHO cells and short-term exposures (3-h ± S9). The Ames assay (TA100 + S9) and the NRU assay were also applied to the gas/vapour phase of the MSS that passed through the Cambridge pad. On a per-milligram-nicotine basis, the preferred way of comparing toxicities of different types of tobacco products, the MSS from cigarillos was not less toxic, and in some cases more toxic (TPM fraction TA98 + S9, NRU), than the MSS from cigarettes. Thus, our findings support our prior work on smoke mutagenicity that showed MSS from cigarillos was not less toxic than MSS from cigarettes.     

Tinospora cordifolia, a safety evaluation

Tinospora cordifolia is one of the indispensable medicinal plants used in veterinary folk medicine/Ayurvedic system of medicine for the treatment of diverse diseases and recommended for improving the immune system by means of body resistance. In the current study, we evaluated the genotoxic risk of the aqueous extract of T. cordifolia (TC) in a battery of four different genotoxicity tests viz., Ames, in vitro chromosome aberration (CA), rodent bone marrow micronucleus (MN), and Comet assay. Experimental results confirmed that in Ames test up to 5000 μg/plate of TC did not exhibit any mutagenic effect in Salmonella typhimurium mutant strains (TA97a, TA98, TA100, TA102, and TA1535). In CA assay, TC was not clastogenic to human peripheral blood lymphocytes up to a concentration of 3000 μg/ml. In MN and Comet assays, TC was pre-treated for 7 days at three dose levels (150, 200 and 250 mg/kg body weight) orally to male Balb/c mice. The results showed that TC treatment did not display clastogenicity and DNA damaging effect in bone marrow erythrocytes and peripheral blood lymphocytes respectively.     

聚乙二醇修饰降纤酶的遗传毒性评价

目的检测聚乙二醇修饰降纤酶的遗传毒性。方法应用鼠伤寒沙门菌回复突变试验(Ames试验)、体外培养CHO细胞染色体畸变试验和小鼠骨髓微核试验检测聚乙二醇修饰降纤酶的遗传毒性。结果 Ames试验结果显示每平皿100、20、4、0.8、0.16 U各个剂量组,在加或不加S9代谢活化系统时对组氨酸缺陷型鼠伤寒沙门菌TA97、TA98、TA100、TA102及TA1535所诱发的回复突变菌落数均与溶剂对照的突变菌落数相近。体外培养CHO细胞染色体畸变试验结果显示2.5、5.0和10.0 U.mL-1各个剂量组在加S9代谢活化系统于24 h和不加S9代谢活化系统于24 h、48 h培养的CHO细胞染色体畸变率与溶剂对照组比较均无显著差异(P>0.05)。小鼠骨髓微核试验显示425、850、1700 U.kg-1各个剂量组对ICR小鼠的微核诱发率与溶剂对照组比较均无显著差异(P>0.05)。结论聚乙二醇修饰降纤酶对鼠伤寒沙门菌无致突变性,对哺乳动物培养细胞的染色体无致畸变作用,对ICR小鼠无诱发骨髓嗜多染红细胞微核的效应。表明聚乙二醇修饰降纤酶在本实验条件下无遗传毒性。     

银参胶囊遗传毒性研究

目的探讨银参胶囊的遗传毒性。方法选用SPF级健康ICR小鼠,通过Ames试验、小鼠骨髓细胞微核试验、小鼠睾丸染色体畸变试验等遗传毒性试验验证银参胶囊的安全性。结果 Ames试验中,银参胶囊在8~5 000μg/皿剂量范围内,无论是否加入哺乳动物肝脏微粒体酶(S9),鼠伤寒沙门菌TA97,TA98,TA100,TA102等4株菌的回复突变菌落数均未出现剂量依赖性增加;微核试验中,2 500,5 000,10 000 mg/kg剂量组均未见骨髓中含微核的嗜多染红细胞数增加;小鼠睾丸染色体畸变试验中,药物质量分数为2 500,5 000,10 000 mg/kg时,细胞的染色体畸变率均未出现剂量依赖性增加。结论银参胶囊未显示致突变作用,可初步判定其在遗传毒性方面是安全的。     

Genotoxicity testing of sodium formononetin-3′-sulphonate (Sul-F) by assessing bacterial reverse mutation,chromosomal aberrations and micronucleus tests

As part of a safety evaluation, we evaluated the potential genotoxicity of sodium formononetin-3′-sulphonate (Sul-F) using bacterial reverse mutation assay, chromosomal aberrations detection, and mouse micronucleus test. In bacterial reverse mutation assay using five strains of Salmonella typhimurium (TA97, TA98, TA100, TA102 and TA1535), Sul-F (250, 500, 1000, 2000, 4000 μg/plate) did not increase the number of revertant colonies in any tester strain with or without S9 mix. In a chromosomal assay using Chinese hamster lung fibroblast (CHL) cells, there were no increases in either kind of aberration at any dose of Sul-F (400, 800, and 1600 μg/mL) treatment groups with or without S9 metabolic activation. In an in vivo bone marrow micronucleus test in ICR mice, Sul-F at up to 2000 mg/kg (intravenous injection) showed no significant increases in the incidence of micronucleated polychromatic erythrocytes, and the proportion of immature erythrocytes to total erythrocytes. The results demonstrated that Sul-F does not show mutagenic or genotoxic potential under these test conditions.     

Genotoxicity of motorcycle exhaust particles in vivo and in vitro.

We studied the genotoxic potency of motorcycle exhaust particles (MEP) by using a bacterial reversion assay and chromosome aberration and micronucleus tests. In the bacterial reversion assay (Ames test), MEP concentration-dependently increased TA98, TA100, and TA102 revertants in the presence of metabolic-activating enzymes. In the chromosome aberration test, MEP concentration-dependently increased abnormal structural chromosomes in CHO-K1 cells both with and without S9. Pretreatment with antioxidants (alpha-tocopherol, ascorbate, catalase, and NAC) showed varying degrees of inhibitory effect on the MEP-induced mutagenic effect and chromosome structural abnormalities. In the in vivo micronucleus test, MEP dose-dependently induced micronucleus formation in peripheral red blood cells after 24 and 48 h of treatment. The increase of micronucleated reticulocytes induced by MEP was inhibited by pretreatment with alpha-tocopherol and ascorbate. The fluorescence intensity of DCFH-DA-loaded CHO-K1 cells was increased upon the addition of MEP. Our data suggest that MEP can induce genotoxicity through a reactive oxygen species-(ROS-) dependent pathway, which can be augmented by metabolic activation. Alpha-tocopherol, ascorbate, catalase, and NAC can inhibit MEP-induced genotoxicity, indicating that ROS might be involved in this effect.     

Developmental toxicity and genotoxicity studies of wogonin

We studied the developmental toxicities and genotoxic potency of a widely bioactive plant medicine-wogonin in vivo and in vitro. In the in vivo developmental experiments, high dose of wogonin (40mg/kg, intravenous injection) significantly induced the maternal weight gains and affected fetus including bodyweight, resorptions, live birth index and fetal skeletal alterations. In Ames test, no concentration-dependently increased TA98, TA100, and TA102 revertants were detected in wogonin groups whether in presence of metabolic activating enzymes or not. In the chromosome aberration test, wogonin dose-dependently increased structural chromosomal aberrations in CHL cells both with and without S9, even the effect was all judged (-). In micronucleus assay, no significant changes of MNPCE/PCE and PCE/NCE were found on mouse bone marrow micronucleus in wogonin groups. We concluded that wogonin induced developmental toxicities on pregnant mice and fetus, and the genotoxicities were positive. However no significant malformation was observed and only in vitro potency of chromosome aberration was weak, which suggested us wogonin could be a relatively safe drug in clinic.     

Genotoxicity of pyrroloquinoline quinone (PQQ) disodium salt (BioPQQ™)

The genotoxic potential of pyrroloquinoline quinone (PQQ) disodium salt (BioPQQ™) was evaluated in a battery of genotoxicity tests. The results of the bacterial mutation assay (Ames test) were negative. Weak positive results were obtained in 2 separate in vitro chromosomal aberration test in Chinese hamster lung (CHL) fibroblasts. Upon testing in an in vitro chromosomal aberration test in human peripheral blood lymphocytes, no genotoxic activity of PQQ was noted. In the in vivo micronucleus assay in mice, PQQ at doses up to 2000 mg/kg body weight demonstrated that no genotoxic effects are expressed in vivo in bone marrow erythrocytes. The weak responses in the in vitro test CHL cells were considered of little relevance under conditions of likely human exposure. PQQ disodium was concluded to have no genotoxic activity in vivo.     

Genotoxic Properties of (E)-5-(2-Bromovinyl)-2'-deoxyuridine (BVDU)

(E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) is a 5-substituted2'-deoxyuridine antiviral compound that inhibits thymidylatesynthetase. The selectivity of BVDU for virus-infected cellshas been attributed to phosphorylation of BVDU by a virus-inducedthymidine kinase. Since the closely related compounds 5-bromo-2'-deoxyuridineand 5-iodo-2'-deoxyuridine are in vitro and in vivo mutagens,BVDU was tested for genotoxic activity in bacterial and mammaliancell mutation assays as well as in assays measuring DNA damage/repairand clastogenic activity. Mutation assays with BVDU at concentrationsranging from 10 to 5000 µg/plate using Salmonella typhimuriumstrains TA1535, TA1537, TA1538, TA98, and TA100 were negative,both with and without S9 activation. BVDU was also negativein the in vitro rat hepatocyte unscheduled DNA synthesis assayat concentrations of 750 and 1000 µg/ml. In contrast,BVDU was positive in the L5178Y TK^± mouse lymphoma mutationassay without S9 activation at five concentrations ranging from500 to 2000 µg/ml. A Chinese hamster ovary cell (CHO)/hypoxanthineguanine phosphoribosyl transferase gene mutation assay conductedwithout S9 over similar concentrations was negative. However,micronucleus induction by BVDU was detected with out S9 activationat concentrations between 500 and 1750 µg/ml using bothCHO and L5178Y cells. These results indicate that BVDU is apotential human clastogen.