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Takamura-Enya T, Ishii R, Oda Y. Evaluation of photo-genotoxicity using the umu test in strains with a high sensitivity to oxidative DNA damage. Mutagenesis 2011; 26:499-505. [DOI: 10.1093/mutage/ger008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Oda Y, Totsuka Y, Wakabayashi K, Guengerich FP, Shimada T. Activation of aminophenylnorharman, aminomethylphenylnorharman and aminophenylharman to genotoxic metabolites by human N-acetyltransferases and cytochrome P450 enzymes expressed in Salmonella typhimurium umu tester strains. Mutagenesis 2006; 21:411-6. [PMID: 17067997 DOI: 10.1093/mutage/gel047] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Norharman (9H-pyrido[3,4-b]indole) and harman (1-methyl-9H-pyrido[3,4-b]indole) contained in cigarette smoke and cooked foodstuffs, are non-mutagenic to Salmonella strains, but show co-mutagenicity with S9 mixture in the presence of aniline or o-toluidine. The resulting 9-(4'-aminophenyl)-9H-pyrido[3,4-b]indole (aminophenylnorharman, APNH), 9-(4'-amino-3'-methylphenyl)-9H-pyrido[3,4-b]indole (aminomethylphenylnorharman, AMPNH) and 9-(4'-aminophenyl)-1-methyl-9H-pyrido[3,4-b]indole (aminophenylharman, APH) are produced by coupling of norharman and aniline, norharman and o-toluidine, and harman and aniline in the presence of S9 mixture, respectively. To clarify the role of human cytochrome P450 (P450) and N-acetyltransferase (NAT) enzymes in the metabolic activation of APNH, AMPNH and APH, we determined the genotoxicity of these coupling chemicals using a variety of umu tester strains established in our laboratories. APNH, AMPNH and APH induced umuC gene expression more strongly in a bacterial O-acetyltransferase-overproducing strain than the parent strain. These chemicals were also found to induce umuC gene expression in NAT2-overexpressing strain at much higher rate than the NAT1-overexpressing strain. Among seven OY strains expressing human P450s and NADPH-P450 reductase used, the genotoxicity of APNH, AMPNH and APH was detected in OY1002/1A2 strain, OY1002/1A1 and OY1002/1A2 strains, and in OY1002/1A2 strain, respectively. From these results, it is concluded that APNH, AMPNH and APH are mainly bioactivated by P450 1A2 and NAT2, followed by NAT1 enzymes. P450 1A1 was also found to activate AMPNH at relatively slower rates.
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Affiliation(s)
- Yoshimitsu Oda
- Osaka Prefectural Institute of Public Health, 3-69 Nanakichi 1-chome, Higashinari-ku, Osaka 537-0025, Japan.
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Wu ZL, Sohl CD, Shimada T, Guengerich FP. Recombinant Enzymes Overexpressed in Bacteria Show Broad Catalytic Specificity of Human Cytochrome P450 2W1 and Limited Activity of Human Cytochrome P450 2S1. Mol Pharmacol 2006; 69:2007-14. [PMID: 16551781 DOI: 10.1124/mol.106.023648] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human cytochromes P450 2S1 and 2W1 have received only limited attention with regard to characterization of function. Both cytochromes P450 have been reported to be overexpressed in human tumors, and cytochrome P450 2S1 is induced by carcinogenic polycyclic hydrocarbons. We report methods for high-level expression and purification of both cytochromes P450 from Escherichia coli, with the goal of establishing function. The level of expression of human cytochrome P450 2W1 achieved using codon optimization for E. coli was 1800 nmol of cytochrome P450 per liter of culture, the highest level achieved in this laboratory to date. Assays with a number of the typical cytochrome P450 substrates showed no detectable activity, including some for which qualitative reports have appeared in the literature. Cytochrome P450 2W1 catalyzed benzphetamine N-demethylation (k(cat), 3.8/min) and arachidonic acid oxidation, albeit at a very low rate (approximately 0.05/min). In a umu genotoxicity screen, cytochrome P450 2W1 catalyzed the activation of several procarcinogens, particularly polycyclic hydrocarbon diols, but cytochrome P450 2S1 did not. The bioactivation of procarcinogens by cytochrome P450 2W1 may be of significance in the context of reports of preferential expression of the enzyme in tumors, in that activation of procarcinogens could lead to the accumulation of mutations and enhance the carcinogenic process.
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Affiliation(s)
- Zhong-Liu Wu
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, 638 Robinson Research Building, 23rd and Pierce Avenues, Nashville, TN 37232-0146, USA
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Wise SS, Schuler JHC, Holmes AL, Katsifis SP, Ketterer ME, Hartsock WJ, Zheng T, Wise JP. Comparison of two particulate hexavalent chromium compounds: Barium chromate is more genotoxic than lead chromate in human lung cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2004; 44:156-162. [PMID: 15278919 DOI: 10.1002/em.20044] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Particulate hexavalent chromium [Cr(VI)] compounds are well-established human lung carcinogens. However, their carcinogenic mechanisms are poorly understood as most investigators have used soluble Cr(VI) compounds. Recent work from our laboratory has found that barium chromate (BC) is also cytotoxic and clastogenic. To understand how BC relates to existing data on other particulate Cr(VI) compounds, we compared its cytotoxicity and clastogenicity with lead chromate (LC), which has been used as a prototypical particulate Cr(VI) compound, in WTHBF-6 cells, a near-normal human lung cell line. We found that BC is a more potent cytotoxicant, inducing 67%, 12%, 3%, and 0% relative survival at concentrations of 0.1, 0.5, 1, and 5 microg/cm2, respectively, while LC induced 90%, 71%, 43%, and 15% survival at these same concentrations. We found that BC was also more clastogenic, damaging 22% and 49% of metaphase cells at 0.1 and 0.5 microg/cm2, and causing complete cell cycle arrest at 1 and 5 microg/cm2. By contrast, 0.1, 0.5, and 1.0 microg/cm2 LC damaged 10%, 27%, and 37% of metaphase cells, respectively, and complete cell cycle arrest was not observed until a concentration of 5 microg/cm2 was reached. We found that BC and LC both partially dissolved in complete medium in the presence of cells, producing similar extracellular concentrations. Both compounds were also comparable with respect to particle uptake and the amount of intracellular Cr ions. Considering previous reports showing that lead ions were inactive and that sodium chromate and LC have similar clastogenic potencies, these data suggest that BC genotoxicity may not be solely mediated by Cr ions, but also involve some clastogenic activity of barium ions.
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Affiliation(s)
- Sandra S Wise
- Wise Laboratory of Environmental and Genetic Toxicology, Center for Integrated and Applied Environmental Toxicology, University of Southern Maine, Portland 04104, USA
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Wise SS, Schuler JHC, Katsifis SP, Wise JP. Barium chromate is cytotoxic and genotoxic to human lung cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2003; 42:274-278. [PMID: 14673872 DOI: 10.1002/em.10203] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Hexavalent chromium (Cr(VI)) compounds are widely accepted as human lung carcinogens. However, there have been few investigations of the genotoxicity of Cr(VI) in human lung cells. Moreover, our knowledge of the effects of Cr(VI) in human lung cells is further limited because the available data generally focus on the effects of only lead chromate (PbCrO(4)) and sodium chromate (Na(2)CrO(4)). To fully understand these carcinogenic compounds, the genotoxic effects to its target cells need to be evaluated for additional Cr(VI) salts. Accordingly, we investigated the cytotoxicity and clastogenicity of barium chromate (BC) in a human lung cell culture model (WTHBF-6 cells). We found that BC induced concentration-dependent cytotoxicity in WTHBF-6 cells, with relative survival of 88%, 74%, 67%, 12%, 3%, and 0.1% after exposure to 0.01, 0.05, 0.1, 0.5, 1, and 5 microg/cm(2) BC, respectively. Similarly, the amount of chromosomal damage also increased with concentration after a 24-h exposure. Specifically, 0.01, 0.05, 0.1, and 0.5 microg/cm(2) BaCrO(4) damaged 5%, 9%, 22%, and 49% of metaphase cells, with the total damage reaching 5, 10, 28, and 65 aberrations per 100 metaphases, respectively. Concentrations of 1 and 5 microg/cm(2) BC induced a profound cell cycle delay, and no metaphases were observed. The spectrum of damage included chromatid and chromosome-type lesions consistent with mechanistic events associated with the activation of oncogenes and inactivation of tumor suppressor genes. Overall the data indicate that BC is cytotoxic and genotoxic to human lung cells.
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Affiliation(s)
- Sandra S Wise
- Center for Integrated and Applied Environmental Toxicology, Wise Laboratory of Environmental and Genetic Toxicology, Bioscience Research Institute, University of Southern Maine, Portland, Maine 04104-9300, USA
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Modesti D, Tanzarella C, Degrassi F. Genotoxic activity of nitrilotriacetic acid in Chinese hamster cells. Mutat Res 1995; 343:1-6. [PMID: 7753103 DOI: 10.1016/0165-1218(95)90057-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Nitrilotriacetic acid (NTA), a chelating agent, was tested for its ability to induce chromosomal damage in Chinese hamster cells. The chemical was shown to exert a weak genotoxic activity increasing the frequency of micronuclei after prolonged treatments. The analysis of kinetochore containing-micronuclei showed that NTA prevailingly induces chromosomal aberrations as compared to chromosome loss in hamster cells. Furthermore, immunostaining with an alpha-tubulin antibody showed clear alterations in the interphase microtubule network of cells treated for 24 h with 3 mM NTA. The microtubule effects of the chemical may be partly responsible for its cytotoxic effects.
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Affiliation(s)
- D Modesti
- Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, Rome, Italy
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Toyokuni S, Sagripanti JL, Hitchins VM. Cytotoxic and mutagenic effects of ferric nitrilotriacetate on L5178Y mouse lymphoma cells. Cancer Lett 1995; 88:157-62. [PMID: 7874688 DOI: 10.1016/0304-3835(94)03641-u] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
An iron chelate, ferric nitrilotriacetate (Fe-NTA), induces renal proximal tubular necrosis that leads to a high incidence of renal adenocarcinoma in rodents. Others have shown that Fe-NTA induces modified DNA base products both in vitro and in vivo. However, Fe-NTA is negative in the Ames Salmonella test with or without S9 activation. The goal of this project was to determine if Fe-NTA is cytotoxic and mutagenic using the L5178Y (TK +/-) mouse lymphoma assay. Our experiments showed a relationship between the concentration of Fe-NTA (0 to 1 mM) and the decrease in relative survival. An exposure-dependent increase in the number of mutations was observed with increasing concentrations of Fe-NTA. At 14% relative survival, there was about a 4-fold increase in mutations (trifluorothymidine resistance) over unexposed, control cells. Ferric nitrate or nitrilotriacetic acid alone induced a relatively low 1.5- or 1.1-fold increase in mutation, respectively. Our results establish that Fe-NTA is mutagenic in the L5178Y mouse lymphoma assay system.
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Affiliation(s)
- S Toyokuni
- U.S. Food and Drug Administration, Rockville, MD 20857
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Tucker JD, Auletta A, Cimino MC, Dearfield KL, Jacobson-Kram D, Tice RR, Carrano AV. Sister-chromatid exchange: second report of the Gene-Tox Program. Mutat Res 1993; 297:101-80. [PMID: 7687323 DOI: 10.1016/0165-1110(93)90001-4] [Citation(s) in RCA: 135] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This paper reviews the ability of a number of chemicals to induce sister-chromatid exchanges (SCEs). The SCE data for animal cells in vivo and in vitro, and human cells in vitro are presented in 6 tables according to their relative effectiveness. A seventh table summarizes what is known about the effects of specific chemicals on SCEs for humans exposed in vivo. The data support the concept that SCEs provide a useful indication of exposure, although the mechanism and biological significance of SCE formation still remain to be elucidated.
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Affiliation(s)
- J D Tucker
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, Livermore, CA 94551
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Connor TH, Pier SM. Reduction of the mutagenicity of lead chromate-based pigments by encapsulation with silica. Mutat Res 1990; 245:129-33. [PMID: 2170838 DOI: 10.1016/0165-7992(90)90012-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
13 lead chromate-based pigments were assayed for mutagenicity and toxicity using Salmonella typhimurium TA100. The compounds were assayed with and without S9, both in the presence and absence of the chelating agent, nitrilotriacetic acid (NTA). In general, the use of NTA to solubilize the compounds resulted in mutagenicity and/or toxicity being observed where it had not in the absence of NTA, or being observed at lower concentrations than when water alone was used. Encapsulation of pigments with amorphous silica rendered these pigments non-mutagenic and non-toxic, indicating that the active moieties were biologically unavailable to the bacteria. Varying the percentage of silica encapsulation on one pigment, medium chrome yellow, indicated that 5% encapsulation did not alter the mutagenicity while 10% encapsulation inhibited the mutagenicity without or with NTA.
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Affiliation(s)
- T H Connor
- University of Texas Health Science Center, School of Public Health, Houston 77225
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Abstract
This article reviews approximately 700 results reported in the literature with 32 chromium compounds assayed in 130 short-term tests, using different targets and/or genetic end-points. The large majority of the results obtained with Cr(VI) compounds were positive, as a function of Cr(VI) solubility and bioavailability to target cells. On the other hand, Cr(III) compounds, although even more reactive than Cr(VI) with purified nucleic acids, did not induce genotoxic effects in the majority of studies using intact cells. Coupled with the findings of metabolic studies, the large data-base generated in short-term test systems provides useful information for predicting and interpreting the peculiar patterns of Cr(VI) carcinogenicity.
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Affiliation(s)
- S De Flora
- Institute of Hygiene and Preventive Medicine, University of Genoa, Italy
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Celotti L, Furlan D, Ferraro P, Levis AG. DNA damage and repair induced in vitro by nitrilotriacetic acid (NTA) in human lymphocytes. Mutat Res 1988; 209:149-54. [PMID: 3193978 DOI: 10.1016/0165-7992(88)90033-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In cultured human lymphocytes we determined the ability of nitrilotriacetic acid (NTA) to inhibit DNA replication and to stimulate DNA repair synthesis (UDS), as well as to influence the UDS induced by UV irradiation. In phytohemagglutinin-stimulated lymphocytes a strong inhibition of DNA replication was induced by NTA concentrations above 10(-3) M, which was accompanied by a marked cell lethality, whereas at lower doses the incorporation of tritiated thymidine (3H-TdR) into DNA or treated cells was slightly increased in comparison to untreated cells. When, after NTA pretreatment, UDS was determined by scintillation spectrometry or autoradiography in unstimulated G0 lymphocytes, UV-irradiated or unirradiated, an increased incorporation of 3H-TdR was observed, positively correlated with the NTA doses. This effect was only partially due to the expansion of the intracellular TdR pool as a consequence of the stimulation of 3H-TdR uptake by NTA. Even after normalization of the scintillometric data by the radioactivities of the soluble nucleotide fraction, significant increase of DNA repair synthesis was detected after treatment with 7.5 x 10(-3)-10(-2) M NTA.
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Lanfranchi G, Paglialunga S, Levis AG. Mammalian cell transformation induced by chromium(VI) compounds in the presence of nitrilotriacetic acid. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1988; 24:251-60. [PMID: 3385800 DOI: 10.1080/15287398809531158] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We used a soft agar assay on cultured Syrian hamster fibroblasts to determine the ability of nitrilotriacetic acid (NTA) and Cr(VI) compounds to induce malignant cell transformation. Induction of extended anchorage-independent growth was detected in BHK 21/c13 cells by scoring colonies of transformed cells visible to the naked eye 20-25 d after plating in growth medium containing agar. Survival was determined by plating cells in liquid medium without agar and by counting the number of macroscopic colonies after 7-10 d. Mitomycin C and 4-nitroquinoline 1-oxide were used as reference direct transforming agents, with clearly positive results. In our hands no increase of the spontaneous transformation rate of BHK cells was induced by NTA concentrations ranging from 2 X 10(-3) to 10(-2) M, although the survival index was significantly reduced above 4 X 10(-3) M NTA. Two Cr(VI) compounds, K2Cr2O7, which is highly soluble in water, and CaCrO4, which is partially soluble, were tested in the soft agar assay either in the absence or in the presence of NTA. When used alone, both compounds behaved as positive transforming agents. NTA increased 4 or 10 times the cytotoxicity and the transforming activity of CaCrO4 and K2Cr2O7, respectively. As the amounts of soluble Cr(VI) detectable in the K2Cr2O7 and CaCrO4 solutions were not increased in the presence of NTA, a synergistic interaction between NTA and soluble Cr(VI) is inferred.
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Affiliation(s)
- G Lanfranchi
- Department of Biology, University of Padua, Italy
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Costa R, Strolego G, Levis AG. Mutagenicity of lead chromate in Drosophila melanogaster in the presence of nitrilotriacetic acid (NTA). Mutat Res 1988; 204:257-61. [PMID: 3125428 DOI: 10.1016/0165-1218(88)90097-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
By using the sex-linked recessive lethal mutation test in Drosophila melanogaster (standard Basc scheme) we analysed the mutagenic effects of treatments by feeding with nitrilotriacetic acid (NTA: 5 X 10(-2) M), with the insoluble Cr(VI) compound lead chromate, PbCrO4 (supernatant of 4.6 X 10(-4)-M suspension in which the actual concentration was 0.06 gamma/ml as Cr(VI)) and with both compounds preincubated at 3 relative ratios (NTA: 5 X 10(-2) M; PbCrO4: 4.6 X 10(-4), 4.6 X 10(-5) and 9.2 X 10(-6) M, respectively). The estimation of mutation frequencies was done at different developmental stages of the germ cells, namely spermatozoa, spermatids and spermatocytes. Ethyl methanesulphonate (EMS: 5 X 10(-3) M) was used as the reference positive control, with clearly mutagenic results. Treatments with NTA or with PbCrO4 alone did not induce any significant increase of the mutation frequency. PbCrO4 at the 3 concentrations tested was completely soluble in the 5 X 10(-2)-M NTA solution, and the mixture of NTA and PbCrO4 induced significant increases of the frequency of sex-linked lethal mutations, with a significant dose-effect relationship with respect to PbCrO4, apparently as a result of the interaction of the compounds and subsequent release of the genotoxic heavy-metal Cr(VI) ions. This result indicates an important synergistic action of NTA with PbCrO4 under the conditions described.
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Affiliation(s)
- R Costa
- Department of Biology, University of Padua, Italy
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Hunter M, da Motta Marques DM, Lester JN, Perry R. A review of the behaviour and utilization of polycarboxylic acids as detergent builders. ACTA ACUST UNITED AC 1988. [DOI: 10.1080/09593338809384534] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Montaldi A, Zentilin L, Paglialunga S, Levis AG. Solubilization by nitrilotriacetic acid (NTA) of genetically active Cr(VI) and Pb(II) from insoluble metal compounds. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1987; 21:387-94. [PMID: 3586067 DOI: 10.1080/15287398709531027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The frequencies of sister chromatid exchanges (SCE) were significantly increased in cultured Chinese hamster cells by insoluble salts of Cr(VI) (PbCrO4) and Pb(II) (PbSO4). A further significant increase of this effect was produced when diluted suspensions of PbCrO4 (1-4 mg/l) and PbSO4 (10-40 mg/l) were preincubated with nitrilotriacetic acid (NTA) concentrations (0.25-1 mg/l) such as those that are possibly found in highly contaminated environmental situations. NTA enhanced the induction of SCE by PbCrO4 and PbSO4 even in the presence, in the preincubation solution and in the medium used to treat the cells, of Na+ and K+ concentrations largely exceeding (e.g., 10(2)-10(6) times) those of the genotoxic metals.
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Celotti L, Furlan D, Seccati L, Levis AG. Interactions of nitrilotriacetic acid (NTA) with Cr(VI) compounds in the induction of gene mutations in cultured mammalian cells. Mutat Res 1987; 190:35-9. [PMID: 3796669 DOI: 10.1016/0165-7992(87)90079-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We used the V79 Chinese hamster cell line to detect the induction by NTA of 6-thioguanine resistance, due to mutation at the HGPRT locus, with direct and indirect mutagens as positive controls. NTA was tested within the 10(-4)-1.5 X 10(-2) M concentration range: although it was cytotoxic above the 10(-2) M dose, it did not increase the frequency of mutations at any of the tested concentrations, independently of metabolic activation (rat-liver S9 fraction). NTA is known to dissolve heavy metals and therefore to increase their genotoxicity. We found that an insoluble Cr(VI) compound, lead chromate (PbCrO4), was not cytotoxic nor mutagenic on V79 cells, probably because it is taken up by the cells very slowly, whereas the presence of NTA (2.5 X 10(-3) M in water) elicited a direct cytotoxicity and mutagenicity, which was dose-dependent from 5 X 10(-5) M to 10(-4) M PbCrO4. This effect was due to solubilization of the chromate anion by NTA, as determined by comparing spectrophotometric determinations of Cr(VI) in PbCrO4 treatment solutions with a mutagenicity titration curve obtained with a completely soluble Cr(VI) salt (potassium dichromate, K2Cr2O7).
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Hunter M, Stephenson T, Kirk PW, Perry R, Lester JN. Effect of salinity gradients and heterotrophic microbial activity on biodegradation of nitrilotriacetic acid in laboratory simulations of the estuarine environment. Appl Environ Microbiol 1986; 51:919-25. [PMID: 3089148 PMCID: PMC238988 DOI: 10.1128/aem.51.5.919-925.1986] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The biodegradation of nitrilotriacetic acid (NTA), a synthetic replacement detergent builder, in the estuarine environment was examined by using a laboratory estuarine simulation. Two interdependent microcosms were used; each of five vessels was equilibrated with a saline gradient between 1.30 and 17.17%, with the final vessel subsequently being increased to a maximum salinity of 31.6%. Each microcosm was seeded simultaneously with heterotrophic bacteria from both fresh and saline sources. Viable counts demonstrated the ability of each microcosm to sustain a mixed heterotrophic bacterial community throughout the range of salinities for 183 days after a stabilization period. Isolation studies demonstrated that both systems contained four bacterial species, representatives of the genera Vibrio and Flavobacterium and members of the coryneform group and the family Enterobacteriaceae. Total bacterial numbers and species diversity decreased with increased salinity. NTA was administered at low and high concentrations, one concentration to each microcosm, initially with the least amount of saline. Removal of both concentrations of NTA occurred and was attributed to biodegradation after a period of bacterial acclimatization. Subsequent dosing of NTA to vessels of higher salinity demonstrated that biodegradation was incomplete at observed mean salinities of greater than 9.18% at low influent NTA concentrations and greater than 5.08% at high influent NTA concentrations. Therefore, acclimatization was dose dependent. It was concluded that NTA acclimatization at the higher salinities ceased because of salinity stress-induced failure of NTA catabolism and not the disappearance of a particular bacterial species.
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