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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
24 November 1993 - 23 December 1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1994
Report Date:
1994

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
EPA OTS 798.5265 (The Salmonella typhimurium Bacterial Reverse Mutation Test)
Deviations:
yes
Remarks:
analysis of the test substance mixtures was not performed
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Exxon Chemical Company/ Lot Number: 2-93-15
- Expiration date of the lot/batch: 31 October 1998

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room Temperature
- Solubility and stability of the test substance in the solvent/vehicle: The test substance was soluble in DMSO.

Method

Species / strain
Species / strain / cell type:
other: S. typhimurium TA 1535, TA 1537, TA 1538, TA 98 and TA 100
Details on mammalian cell type (if applicable):
CELLS USED
- Source of cells: Dr. B. N. Ames, Department of Biochemistry, University of California, Berkeley, California.
Metabolic activation:
with and without
Metabolic activation system:
Liver homogenate from the livers of Aroclor 1254 pretreated Sprague Dawley rats
Test concentrations with justification for top dose:
625, 1250, 1500, 500, 10000 ug/ml.

In a toxicity pretest a dose range from 1 to 10,000 ug per plate where tested. An increase in the number of revertant colonies was not observed at any of the concentrations tested. A reduction in the number of revertant colonies was observed at test concentrations 50 ug/plate and 10,000 ug/plate. It is was clear if this decrease is related to toxicity or the normal variation in colony counts. The test substance appeared to bead on the plates at test concentrations of 2,000 to 10,000 ug/plate.
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
9-aminoacridine
2-nitrofluorene
other: 2-Aminoanthracene, N-Methyl-N-Nitro-N-Nitrosoguanidine
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar

DURATION
- Exposure duration: 2 days
Evaluation criteria:
An individual dose is considered positive if the mean colony count on the test plates is equal to or greater than three times the mean number of spontaneous revertants on the vehicle control plates. A positive result for the assay is defined as a reproducible dose-related increase in the number of revertant colonies over at least 3 concentrations of test material including at least one positive dose
Statistics:
The mean plate count and standard deviation for each dose point were determined.

Results and discussion

Test results
Key result
Species / strain:
other: S. typhimurium TA 1535, TA 1537, TA 1538, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid

Any other information on results incl. tables

Results tables can be found in the attachment to this RSS.

Applicant's summary and conclusion

Conclusions:
Exxate 1300 (MRD-93-689) was not considered to be mutagenic under the conditions of this assay.
Executive summary:

The microbial mutagenesis assay (Ames Assay), developed by B. N. Ames and coworkers (1975) is a test for the ability of a compound to cause reverse mutation at the histidine locus in bacteria (from nutritional histidine dependence to histidine independence). Five special tester strains of Salmonella typhimurium, which were sensitive to frameshift or base pair mutagens, were employed. Positive test results are considered to provide presumptive evidence of mutagenic potential in mammalian species.

This assay was conducted in compliance with the U.S. EPA, Federal Insecticide, Fungicide and Rodenticide Act (FIFRA); Good Laboratory Practice Standards, 40 CFR Part 160, 1989 and the U.S. EPA, Toxic Substance and Control Act (TSCA) Test Guidelines 40 CFR 798.5265, 1985, to determine if Exxate 1300 (MRD-93-689) was capable of causing reverse mutations in these special tester strains of bacteria with and without metabolic activation.

The test substance was diluted in DMSO. A toxicity pretest was performed to determine the highest concentration of test substance to be used in the initial assay. Test concentrations of 1 to 10,000 µg/plate were tested with and without metabolic activation in tester strain TA98.

The test substance did not induce an increase in the number of revertant colonies at any of the concentrations tested. A reduction in the number of revertant colonies was observed at test concentrations 50 µg/plate and 10,000 µg/plate without metabolic activation. It is not clear if this decrease is related to toxicity or the normal variation of colony counts.

Based on these results, test concentrations of 625 to 10,000 µg/plate were tested in the initial assay. A repeat assay was performed using test concentrations of 156 to 2,500 µg/plate.

Neither a positive dose nor a dose related increase was observed for any of the tester strains with or without metabolic activation. Thus, Exxate 1300 (MRD-93-689) was not considered to be mutagenic under the various conditions of testing.

Toxicity, as seen by either a reduction in the number of reverent colonies or reduction in the background lawn, was not observed.

Both the negative and positive controls responded in an appropriate manner.