Document MMnY8Ly638a0KVNxpxN6pGvj9

I IN VITRO MICROBIOLOGICAL MUTAGENICITY ASSAYS OF 3M COMPANY'S COMPOUND T-2997CoC Final Report January 1981 Prepared for: 3M COMPANY Medical Department General Offices, 3M Center St. Paul, Minnesota 55101 Attention: Mr. William C. McCormick Toxicology Services, 220-2E-02 SRI Project LSC-8958 Approved by: 0 Ta. ^ David C. L. Jonefe, Director Toxicology Laboratory u .a. xx W. A. Skinner, Executive Director Life Sciences Division 333 Ravenswood Ave. Menlo Park, California 94025 (415) 326-6200 C able: SRI INTL MPK TW X: 910-373-1246 SUMMARY SRI International examined 3M Company's Compound T-2997CoC for mutagenic activity with strains TA1535, TA1537, TA1538, TA98, and TA100 of Salmonella tvphimurium in the standard Ames Salmonella/microsome assay and with the yeast Saccharomvces cerevisiae D3 using FDA-approved GLP procedures. Each assay was performed in the presence and in the absence of a rat liver metabolic activation system. Compound T-2997CoC was not mutagenic m recombinogenic in any assay performed. 11 CONTENTS S U M M A R Y ............................................ QUALITY' ASSURANCES T A T E M E N T ......................... INTRODUCTION ........................................ MATERIALS .......................................... METHODS ............................................ RESULTS AND DISCUSSION .............................. TABLES Table 1 ........................................ Table 2 ........................................ Table 3 ........................................ Table 4 ........................................ ii iv 1 2 3 9 10 11 12 13 iii QUALITY ASSURANCE UNIT Final Report Statement SRI International assures the quality and integrity of this study, the Ames Salmonella Microsome assay and the Saccharomyces cerevisiae D3 recombinogenic assay of the 3M Company's compounds T-2997 CoC. The study was inspected on December 12 and 22, 1980 during the dilution, plating, and plate counting of the two assays. The findings of the Quality Assurance Unit Inspector were reported at the time of each inspection to the Study Director. SRI management was also informed of the inspection results on December 12 and 22, 1980, respectively. This final report accurately describes the methods and standard operating procedures and reflects the raw data of the study. Any deviations from the approved protocol and standard operating procedures were made with proper authorization and documentation. iv INTRODUCTION SRI International examined 3M Company's Compound T-2997CoC for mutagenicity by in vitro microbiological assays with strains TA1535, TA1537, TA1538, TA98, and TA100 of the bacterium Salmonella typhimurium in the standard Ames Salmonella/microsome assay and with the yeast Saccharomvces cerevisiae D3. An Aroclor 1254-stimulated, rat liver homogenate metabolic activation system was included in the assay procedures to provide metabolic steps that the bacteria either are incapable of conducting or do not carry out under the assay conditions. The assay procedure with _S. typhimurium has proven to be 80 to 90% reliable in detecting carcinogens as mutagens, and it has about the same reliability in identifying chemicals that are not carcinogenic. The assay procedure with _S. cerevisiae is about 60% reliable in detect ing carcinogens as agents that increase mitotic recombination. However, because the assay systems do not always provide 100% correlation with carcinogenicity investigations in animals, neither a positive nor a negative response conclusively proves that a chemical is carcinogenic or noncarcinogenic to man. The assays with Compound T-2997CoC were begun on 12 December 1980 and completed on 7 January 1981. Copies of the final report will be kept in our files (Building 28, Room 213) and in SRI's Records Center. The laboratory notebook will be retained in Building 28A, Room 10 for one year after it is filled, and then will be stored in SRI's Record Center. All that is left of Compound T-2997CoC will be kept for six months in our chemical storage room (Building 28, Room 217), then returned to the 3M Company. 1 MATERIALS Test Compounds - Name: T-2997CoC. - Date Received: 8 December 1980. - Description: Waxy amber solid. - Stability: Stability assured by client. - Storage Condition: Stored at room temperature. - Special Testing Conditions: None. Indicator Organisms - Species: Salmonella typhimurium LT2 and Saccharomyces cerevisiae. - Strains: TA1535, TA1537, TA1538, TA98, and TA100 of _S. typhimurium; D3 of _S. cerevisiae. Metabolic Activation Aroclor 125L-induced rat liver S--9; SRI Batch D7, D 8 , and NIEHS RLI003, v 30 mg/ml protein. Solvent Lsed Dimethylsulfoxide (DMSO). 2 METHODS Salmonella tvphimurium Strains TA1535, TA1537, TA1538, TA98. and TA100 The Salmonella typhimurium strains used at SRI are all histidine auxotrophs by virtue of mutations in the histidine operon. When these histidine-dependent cells are grown on minimal medium agar plates con taining a trace of histidine, only those cells that revert to histidine independence (his'1') are able to form colonies. The small amount of histidine allows all the plated bacteria to undergo a few divisions; in many cases, this growth is essential for mutagenesis to occur. The his+ revertants are easily visible as colonies against the slight background growth. The spontaneous mutation frequency of each strain is relatively constant, but when a mutagen is added to the agar, the mutation frequency is increased, usually in a dose-related manner. We obtained our S^. typhimurium strains from Dr. Bruce Ames of the University of California at Berkeley. In addition to having mutations in the histidine operon, all the indicator strains have a mutation (rfa) that leads to a defective lipopolysaccharide coat; they also have a deletion that covers genes involved in the synthesis of the vitamin biotin (bio) and in the repair of ultraviolet (uv)-induced DNA damage (uvrB) . The rfa mutation makes the strains more permeable to many large molecules, thereby increasing the mutagenic effect of these molecules. The uvrB mutation causes decreased repair of some types of chemically or physically damaged DNA and thereby enhances the strains' sensitivity to some mutagenic agents. Strain TA1535 is reverted to his_+ by many mutagens that cause base-pair substitutions. TA100 is derived from TA1535 by i h e introduction of the resistance transfer faccor, plasmid pKMIOl. This plasmid is believed to cause an increase in error-prone DNA repair that leads to many more mutations for a given dose of most mutagens. In addition, plasmid pKMIOl confers resistance to the anti biotic ampicillin, which is a convenient marker to detect the presence 3 of the plasmid in the cell. The presence of this plasmid also makes strain TA100 sensitive to some frameshift mutagens [e.g., ICR-191, benzo(a)pyrene, aflatoxin B x, and 7,12-dimethylbenz(a)anthracene]. Strains TA1537 and TA1538 are reverted by many frameshift mutagens. Strain TA98 is derived from TA1538 by the addition of the plasmid pKMIOl, which makes it more sensitive to some mutagenic agents. All indicator strains are kept at 4C on minimal agar plates supple mented with an excess of biotin and histidine. The plates with the plasmid-carrying strains also contain ampicillin (25 yg/ml) to ensure stable maintenance of the plasmid pKMIOl. New stock culture plates are made every A to 6 week* from sing1*" colony ^so1etes that have beer checked for their genotypic characteristics (his, rfa, uvrB, bio) and for the presence of the plasmid. For each experiment, an inoculum from the stock culture plates is grown overnight at 37C in nutrient broth (OXOID, CM67). Aroclor 125A-Stimulated Metabolic Activation System Some carcinogenic chemicals (e.g., of the aromatic amino type or the polycyclic hydrocarbon type) are inactive unless they are metabolized to active forms. In animals and man, an enzyme system in the liver or other organs (e.g., lung or kidney) is capable of metabolizing a large number of these chemicals to carcinogens. Some of these intermediate metabolites are very potent mutagens in the S^. typhimurium test. Ames has described the liver metabolic activation system that we use. In brief, adult male rats (250 to 300 g) are given a single 500 mg/kg intraperitoneal injection of Aroclor 1254 (a mixture of polychlorinated biphenyls). This treatment enhances the synthesis of enzymes involved in the metabolic conversion of chemicals. Four days after the injection, the animals' food is removed but drinking water is provided ad libitum. On the fifth day, the rats are killed and the liver homogenate is prepared as follows. The livers are removed aseptically and placed in a preweighed sterile glass beaker. The organ weight is determined, and all sub sequent operations are conducted in an ice bath. The livers are washed A with an equal volume of cold, sterile 0.15 M KC1 (1 ml/g of wet organ), minced with sterile surgical scissors in three volumes of 0.15 M KC1, and homogenized with a Potter-Elvehjem apparatus. The homogenate is centrifuged for 10 minutes at 9000 * , and the supernatant, referred to as the S-9 fraction, is quickly frozen in dry ice and stored at -80C. The metabolic activation mixture for each experiments consists o f , for 10 ml: 1.00 ml of S-9 fraction 0.20 ml of MgCla (0.4 M) and KC1 (1.65 M) 0.05 ml of glucose-6-phosohate (1 M) 0.40 ml of NADP (0.1 M) 5.00 ml of sodium phosphate buffer (0.2 M, pH 7.4) 3.35 ml of Ha0. Assavs in Agar To a sterile 13 * 100 mm test tube placed in a 43C heating block, we add in the following order: (1) 2.00 ml of 0.6% agar (2) 0.05 ml of indicator organisms (3) 0.50 ml of metabolic activation mixture (if appropriate) (4) 0.05 ml of a solution of the test chemical. This mixture is stirred gently and then poured onto minimal agar plates. After the top agar has set, the plates are incubated at 37C for 2 days. The number of _his+ revertant colonies is counted and recorded. For negative controls, we use steps (1), (2), and (3) and 0.05 ml of the solvent used for the test chemical. Dimethylsulfoxide (DMSO) was used as the solvent for T-2476ChR. For positive controls, we test each * The 0.6% agar contains 0.05 mM histidine, 0.05 mM biotin, and 0.6% NaCl. ^Minimal agar plates consist of, per liter, 15 g of agar, 10 g of glucose, 0.2 g of MgS0fc7Ha0, 2 g of citric acid monohydrate, 10 g of K 2HP0fc, and 3.5 g of NaNHfcHP0*4Ha0. 5 culture by specific mutagens known to revert each strain, using steps (1) , (2) , (3) , and (4). Saccharomvces cerevisiae D3 The yeast J3. cerevisiae D3 is a diploid microorganism heterozygous for a mutation leading to a defective enzyme in the adenine-metabolizing pathway. When grown on medium containing adenine, cells homozygous for this mutation produce a red pigment. These homozygous mutants can be generated from the heterozygotes by mitotic recombination. The frequency of this recombinational event may be increased by incubating the organisms with various carcinogenic or recombinogenic agents. The recuaibiiiOgeuic activity of a compound or its metabolite is determined from the number of red-pigmented colonies appearing on test plates. A stock culture of j>. cerevisiae is stored at 4C. For each experiment, broth containing 0.05% MgSO*, 0.15% KHjPOi,, 0.45% (NHi.)aSOfc, 0.35% peptone, 0.5% yeast extract, and 2% dextrose is inoculated with a loopful of the stock culture and incubated overnight at 30C with shaking. The in vitro yeast mitotic recombination assay in suspension is conducted as follows. The overnight culture is centrifuged and the cells are resuspended at a concentration of 10* cells/ml in 67 mM phosphate buffer (pH 7.4). To a sterile test tube are added; 1.00 ml of the resuspended culture 0.50 ml of either the metabolic activation mixture or buffer 0.20 ml of the test chemical 0.30 ml of buffer. Several doses of the test chemical are tested in each experiment, and appropriate controls are included. The suspension mixture is incubated at 30C for A hours on a roller drum. The sample is then diluted serially in sterile physiologic saline, and 0.2 ml of the 10-5 and 10~s dilutions is spread on plates containing the same ingredients as the broth plus 2.0% agar; five plates 6 are spread with the 10" 3 dilution and three plates are spread with the 10-s dilution. The plates are incubated for 2 days at 30C, followed by 2 days at 4C to enhance the development of the red pigment indicative of adenine-deficient homozygosity. Plates containing the 10" 3 dilution are scanned with a dissecting microscope at 10* magnification, and the number of mitotic recombinants (red colonies or red sectors) is recorded. The surviving fraction of organisms is determined from the total number of colonies appearing on the plates of the 10-s dilution. The number of mitotic recombinants is calculated per 10s survivors. A positive response in this assay is indicated by a dose-related increase of more than 3-fold in the absolute number of mitotic recombinant milliliter as well as in the relative number of mitotic recombinants per 10s survivors. Statistical Method No statistical method was needed. Results are a tabulation of the number of colonies appearing on the plates after incubation. References Ames, B. N., E. G. Gurney, J. A. Miller, and H. Bartsch. Carcinogens as frameshift mutagens: Metabolites and derivatives of 2-acetylaminofluorene and other aromatic amine carcinogens. Prcc. Nat. Acad. Sci. USA 69, 3128-3132 (1972). Ames, B. N . , W. E. Durston, E. Yamasaki, and F. D. Lee. Carcinogens are mutagens: A simple test system combining liver homogenates for activa tion and bacteria for detection. Proc. Nat. Acad. Sci. USA 70, 2281 2285 (1973). Ames, B. N . , F. D. Lee, and W. E. Durston. An improved bacterial test system for the detection and classification of mutagens and carcinogens. Proc. Nat Acad. Sci. USA 70, 782-786 (1973). Ames, B. N., J. McCann, and E. Yamasaki. Methods for detecting carcinogens and mutagens with the Salmone11a/mammalian-microsome mutagenicity test. Mutation Res. 31, 347-364 (1975). Brusick, D. J., and V. W. Mayer. screening techniques with yeast. (1973). New developments in mutagenicity Environ. Health Perspectives b, 83-86 7 Kier, L. D., E. Yamasaki, and B. N. Ames. Detection of mutagenic activity in cigarette smoke condensates. Proc. Nat. Acad. Sci. USA 71, 4159-4163 (1974). McCann, J., E. Choi, E. Yamasaki, and B. N . Ames. Detection of carcino gens as mutagens in the Salmonella/microsome test: Assay of 300 chemicals. Proc. Nat. Acad. Sci. USA ]2_, 5135-5139 (1975). McCann, J., N. E. Spingarn, J. Kobori, and B. N. Ames. Detection of carcinogens as mutagens: Bacterial tester strains with R Factor plasmids. Proc. Nat. Acad. Sci. USA _72, 979-983 (1975). Mortelmans, K. E . , and B.A.D. Stocker. Segregation of the mutator property of plasmid R46 from its ultraviolet-protecting property. Mol. Gen. Genet. 167, 317-327 (1979). Zinlinermann, F. K. , an- R. Sc'nwaier. Tndu--Liun or mitotic gene conversion with nitrous acid, l-methyl-3-nitro-l-nitrosoguanidine and other alky lating agents in Saccharomvces cerevisiae. Mol. Gen. Genet. 100, 63-69 (1967). 8 RESULTS AND DISCUSSION Compound T-2997CoC was tested for mutagenicity with the Ames Salmonella/microsome assay and with the yeast Saccharomyces cerevisiae D3 assay in the presence and in the absence of a metabolic activation system. The compound was tested twice on separate days in both assays. Dimethylsulfoxide (DMSO) was used as the solvent in all assays. In the Ames Salmonella/microsome assay, Compound T-2997CoC was tested over a wide range of concentrations, from 10 to 5,000 yg/plate (Table 1). Because no toxicity occurred at 5,000 yg/plate, the second test was run using a higher dose range, from 50 to 10,000 yg/plate (Table 2). Still no toxicity or dose-related increase in the number of revertants per plate was observed in either assay. In the microbiological assays with S_. cerevisiae D 3 , T-2997CoC was tested over a wide range of concentrations, from 0.05 to 5.0% w/v (Tables 3 and 4). No toxicity or dose-related increase in the number of mitotic recombinants was observed in either assay. We conclude that Compound T-2997CoC is not mutagenic with _S. tvphimurium or recombinogenic in S_. cerevisiae. 9 Table 1 IN VITRO ASSAYS WITH SALMONELLA TYPItlMURIUM COMPOUND T-2997CoC Experiment Date: 12 December 1980 Compound Metaboli c Act ivat Ion Compound Added (pg/plate) Negative Control DMSO Positive Controls Sodium Azide 9-Aminoacrid ine 2-Nitrofluorene 2-Anthramine Compound T-2997CoC + - - + + _ _ _ - + + + + + + 1.0 50.0 5.0 1.0 1.0 2.5 2.5 10.0 50.0 100.0 500.0 1,000.0 5,000.0 10.0 50.0 100.0 500.0 1,000.0 5,000 0 TA 1535 15 16 16 13 336 324 9 20 252 275 24 27 19 17 19 16 28 15 30 15 20 19 76 15 9 3 14 9 13 16 8 9 16 Histidine Rever tants per Plat u TA 153 7 TAJ 538 TA98 TA100 57 73 12 7 18 9 20 16 38 31 115 130 104 110 508 527 77 77 101 35 34 56 55 68 73 12 12 85 77 59 9 16 13 8 726 738 17 7 271 294 57 2 13 12 8 59 58 87 13 12 18 14 12 7 16 19 21 26 7 16 467 442 372 381 38 37 158 147 126 140 519 518 26 29 24 31 21 32 18 28 25 24 18 30 36 43 38 28 26 49 37 40 34 33 31 24 99 149 124 116 115 112 99 129 111 113 101 97 122 135 125 125 108 112 126 134 129 127 105 92 Table 2 IN VITRO ASSAYS WITH SAI.MONKUJ\ TYPH1MURIUM COMPOUND T-2997CoC Experiment Date: 15 December 1980 Compound Metabol ic Act 1vat Ion Compound Addl'd (pg/plate) Negative Control DMSO Positive Controls Sodium Azide 9-Aminoacridine 2-Nitrofluorene 2-Anthramine Compound T-2997CoC - + - - + - + - + + + + + + 1 .0 50.0 5.0 1.0 1.0 2.5 2.5 50.0 100.0 500.0 1,000.0 5,000.0 10,000.0 50.0 100.0 500.0 1,000.0 5,000.0 10,000.0 TAL535 24 15 68 224 276 13 14 257 209 16 9 17 8 15 9 16 17 13 12 9 15 69 77 6 12 5 15 45 67 Histidine Reve rtants per Plate 'TA15 17 TA1538 TA98 14 8 78 8 13 25 8 25 24 18 27 721 604 16 8 64 51 5 13 8 15 73 22 68 16 59 88 76 65 44 56 691 863 9 15 154 149 13 12 9 12 94 88 46 47 5 19 14 14 17 9 15 13 15 9 12 14 337 420 15 18 153 161 12 25 17 19 20 16 17 16 7 12 14 20 24 37 18 32 19 19 16 22 20 21 17 16 TA100 100 110 99 108 317 347 93 72 383 357 108 125 79 108 88 112 80 113 72 97 54 57 91 114 86 123 108 103 93 105 98 104 88 97 Compound Negative Control DMSO Positive Control 1,2,3,4-Diepoxybutane Compound T-2997CoC Table 3 IN VITRO ASSAYS WITH SACCHAROMYCES CEREVISIAE D3 COMPOUND T-2997CoC Experiment Date: 17 December 1980 Metabol1c Activation Percent Survivors Concentration Cells per ml (w/v or v/v) (x 10 7) Percent Mitotic Recombinants Per ml Per 10s (x 10 3) Survivors 7.4 100 2.0 2.8 + 6.5 100 2.0 3.0 - 0.025 + 0.025 - .05 - .1 - .5 - 1.0 - 5.0 + .05 + .1 + .5 + 1.0 + 5.0 6.6 89 1100.0 5.2 80 530.0 6.5 88 7.0 95 6.2 84 6.4 86 6.5 88 7.0 103 5.9 91 6.4 98 6.2 95 6.5 100 1.0 1.0 1.0 1.0 3.0 1.0 1.0 1.0 1.0 2.0 1700.0 1000.0 1.5 1.4 1.6 1.6 4.6 1.4 1.7 1.6 1.6 3.1 Compound Negative Control DMSO Positive Control 1,2,3,4-Diepoxybutane Compound T-2997CoC t Table 4 IN VITRO ASSAYS WITH SACCHAROMYCES CEREVISIAE D3 COMPOUND T-2997CoC Experiment Date : 7 January 1981 Metabolic Activation Percent Survivors Concentration Cells per ml (w/v or v/v) (x 10_7) Percent Mitotic Recombinants Per ml Per 104 (x 10 3) Survivors - 6.8 100 5.0 7.5 + 6.5 100 3.5 5.4 - 0.025 5.1 75 900.0 1800.0 + 0.025 5.6 86 1000.0 1800.0 - .05 - .1 - .5 - 1.0 - 5.0 + .05 + .1 + .5 + 1.0 + 5.0 6.4 9o 6.4 9`t 6.9 101 6.7 99 5.0 74 6.1 94 6.7 103 6.5 100 5.4 83 6.3 97 2.0 4.0 3.0 1.0 6.0 2.0 8.0 5.0 3.0 7.0 3.1 6.3 4.3 1.5 12.0 3.3 12.0 7.7 5.6 11.0