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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
7 March 2001 to 9 April 2001
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Method

Target gene:
S. typhimurium: histidine
E. coli: tryptophan
Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Additional strain / cell type characteristics:
other: a deletion through the excision repair gene (uvrB- Salmonella strains) which renders the organism incapable of DNA excision repair and deep rough mutation (rfa) which increases the permeability of the cell wall
Species / strain / cell type:
E. coli WP2 uvr A
Additional strain / cell type characteristics:
other: a deletion in an excision repair gene (uvrA-)
Metabolic activation:
with and without
Metabolic activation system:
Phenobarbital/beta-naphthoflavone-induced rat liver S9-mix
Test concentrations with justification for top dose:
Concentration range in the main test (with and without metabolic activation): 50, 150, 500, 1500 and 5000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: NDA
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
Remarks:
DMSO
True negative controls:
yes
Remarks:
2-Aminoanthracene (2AA) and Benzo(a)pyrene (BP), which are non-mutagenic in the absence of metabolising enzymes, were used: 2AA at 1 µg/plate for TA100. 2AA at 2 µg/plate for TA1535 and TA1537. BP at 5 µg/plate for TA98. 2AA at 10 µg/plate for WP2uvrA-
Positive controls:
yes
Positive control substance:
other: N-ethyl-N'-nitro-N-nitrosoguanidine(ENNG): 3 µg/plate for TA100; 5 mg/plate for TA1535 and 2 4g/plate for WP2uvrA. 9-Aminoacridine (9AA): 80 µg/plate for TA1537. 4-Nitroquinoline-l-oxide (4NQO): 0.2 µg/plate for TA98.
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)
Measured aliquots (0.1 ml) of one of the bacterial cultures were dispensed into sets of test tubes followed by 2.0 ml of molten, trace histidine or tryptophan supplemented, top agar, 0.1 ml of the test material formulation, vehicle or positive control and either 0.5 ml of S9-mix or phosphate buffer. The contents of each test tube were mixed and equally distributed onto the surface of Vogel-Bonner Minimal agar plates (one tube per plate). This procedure was repeated, in triplicate, for each bacterial strain and for each concentration of test material both with and without S9-mix.

All of the plates were incubated at 37°C for approximately 48 hours and the frequency of revertant colonies assessed using a Domino colony counter.

NUMBER OF REPLICATIONS: Triplicate, for each bacterial strain and for each concentration of test material both with and without S9-mix

NUMBER OF CELLS EVALUATED: NDA

DETERMINATION OF CYTOTOXICITY
The cytotoxicity of the test material was determined in a dose range finding study:
The dose range for the test material used was 0, 0.15, 0.5, 1.5, 5, 15, 50, 150, 500, 1500 and 5000 µg/plate. The test was performed by mixing 0.1 ml of bacterial culture (TA100 or WP2uvrA-), 2 ml of molten, trace histidine or tryptophan supplemented, top agar, 0.1 ml of test material formulation and 0.5 ml of S9-mix or phosphate buffer and overlaying onto sterile plates of Vogel-Bonner Minimal agar (30 ml/plate). Ten concentrations of the test material formulation and a vehicle control (dimethyl sulphoxide) were tested. In addition, 0.1 ml of the maximum concentration of the test material and 2 ml of molten. trace histidine supplemented. top agar was overlaid onto a sterile Nutrient agar plate in order to assess the sterility of the test material. After approximately 48 hours incubation at 37°C the plates were assessed for numbers of revertant colonies using a Domino colony counter and examined for effects on the growth of the bacterial background lawn.
The test material was non-toxic to the strains of bacteria used (TA100 and WP2uvrA-). The test material formulation and S9-mix used in this experiment were both shown to be sterile.

No cytotoxicity was observed in the dose range finding study so the highest dose of test article used in the mutagenicity assay was the same as that tested in the range finding study.

OTHER EXAMINATIONS: None
Evaluation criteria:
The reverse mutation assay may be considered valid if the following criteria are met:
All tester strain cultures exhibit a characteristic number of spontaneous revertants per plate in the vehicle and untreated controls.
The appropriate characteristics for each tester strain have been confirmed, eg rfa cell-wall mutation and pkM 101 plasmid R-factor etc.
All tester strain cultures should be in the approximate range of 1 to 9.9 x 10^9 bacteria per ml.
Each mean positive control value should be at least two times the respective vehicle control value for each strain, thus demonstrating both the intrinsic sensitivity of the tester strains to mutagenic exposure and the integrity of the S9-mix.
There should be a minimum of four non-toxic test material dose levels.
There should be no evidence of excessive contamination.

The test material may be considered positive in this test system if the following criteria are met:
The test material should have induced a reproducible, dose-related and statistically (Dunnett's method of linear regression) significant increase in the revertant count in at least one strain of bacteria.
Statistics:
Dunnett's method of linear regression

Results and discussion

Test resultsopen allclose all
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Preliminary Toxicity Study:

The test material was non-toxic to the strains of bacteria used (TA100 and WP2uvrA-). The test material formulation and S9-mix used in this experiment were both shown to be sterile.

Main Study:

Prior to use, the master strains were checked for characteristics, viability and spontaneous reversion rate (all were found to be satisfactory). These data are not given in the study report. The S9-mix used in both experiments was shown to be sterile.

Results for the negative controls (spontaneous mutation rates) were considered to be acceptable. These data are for concurrent untreated control plates performed on the same day as the Mutation Study.

The test material caused no visible reduction in the growth of the bacterial background lawn at any dose level. The test material was, therefore, tested up to the maximum recommended dose level of 5000 µg/plate. No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation.

All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies thus confirming the activity of the S9-mix and the sensitivity of the bacterial strains.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'. Remarks: main test

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative with metabolic activation
negative without metabolic activation

The test material was considered to be non-mutagenic under the conditions of this test.
Executive summary:

In a reverse gene mutation assay in bacteria, strains S. typhimurium TA 1535, TA 1537, TA 98 and TA 100 and E. coli were exposed to Experimental 11214-70 in dimethyl sulphoxide at concentrations of 50, 150, 500, 1500 and 5000 μg/plate in the presence and absence of mammalian metabolic activation.

Experimental 11214-70 was tested up to a limit concentration of 5000 μg/plate, based on a lack of cytotoxic responses exhibited in a preliminary study. The positive controls induced the appropriate responses in the corresponding strains. There was no evidence of induced mutant colonies over background.

The results of this study were negative and the substance was found to be non-mutagenic.