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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:
14 July 2017 to 22 September 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Details on test material:
purity >85 % (w/w)

Method

Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Details on mammalian cell type (if applicable):
The bacteria used in this assay did not possess the mammalian enzyme system that is known to convert promutagens into mutagenic metabolites.
Additional strain / cell type characteristics:
not applicable
Species / strain / cell type:
E. coli WP2 uvr A
Details on mammalian cell type (if applicable):
The bacteria used in this assay did not possess the mammalian enzyme system that is known to convert promutagens into mutagenic metabolites.
Additional strain / cell type characteristics:
not applicable
Metabolic activation:
with and without
Metabolic activation system:
cofactor-supplemented post-mitochondrial S9 fraction
Test concentrations with justification for top dose:
The maximum concentration was 5000 ug/plate (the maximum recommended dose level). In experiment 1, eight concentrations of the test item (1.5, 5, 15, 50, 150, 500, 1500 and 5000 ug/plate) were assayed in triplicate against each tester strain, both with and without the addition of a rat liver homogenate metabolizing system (10% liver S9 in standard co-factors). The experiment was repeated on a separate day (pre-incubation method) using fresh cultures of the bacterial strains and fresh test item formulations. The dose range used for Experiment 2 was determined by the results of Experiment 1 and was 15, 50, 150, 500, 1500, 5000 μg/plate. Six test item concentrations per bacterial strain were selected in Experiment 2 in order to achieve both four non-toxic dose levels and the potential toxic limit of the test item following the change in test methodology from plate incorporation to pre-incubation.
Vehicle / solvent:
sterile distilled water
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
Remarks:
sterile distilled water
Positive controls:
yes
Positive control substance:
2-acetylaminofluorene
4-nitroquinoline-N-oxide
9-aminoacridine
N-ethyl-N-nitro-N-nitrosoguanidine
benzo(a)pyrene
Details on test system and experimental conditions:
Both the Ames plate incorporation and pre-incubation methods were used.
Rationale for test conditions:
The maximum dose level of the test item in the first experiment was selected as the maximum recommended dose level of 5000 μg/plate. There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the first mutation test (plate incorporation method). Consequently, the same maximum dose level was used as the maximum concentration in the second mutation test. Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the second mutation test (pre-incubation method)
Evaluation criteria:
There were several criteria used for determining a positive result. Any, one, or all of the following were used to determine the overall result of the study:
1. A dose-related increase in mutant frequency over the dose range tested (De Serres and Shelby, 1979).
2. A reproducible increase at one or more concentrations
3. Biological relevance against in-house historical control ranges
4. Statistical analysis of data as determined by UKEMS (Mahon et al., 1989)
5. Fold increase greater than two times the concurrent solvent control for any tester strain (especially if accompanied by an out-of-historical range response (Cariello and Piegorsch, 1996)
A test item is considered non-mutagenic (negative) in the test system if the above criteria are not met.
Statistics:
Statistical significance was confirmed by using Dunnetts Regression Analysis (* = p < 0.05) for those values that indicate statistically significant increases in the frequency of revertant colonies compared to the concurrent solvent control. Values that the program concluded as statistically significant but were within the in-house historical profile were not reported.

Results and discussion

Test resultsopen allclose all
Key result
Species / strain:
S. typhimurium TA 1535
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
Key result
Species / strain:
S. typhimurium TA 1537
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
Key result
Species / strain:
S. typhimurium 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
Key result
Species / strain:
S. typhimurium TA 98
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
Key result
Species / strain:
E. coli WP2 uvr A
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

Applicant's summary and conclusion

Conclusions:
The test item is non-mutagenic in the Ames test both in the presence and in the absence of metabolic activation.
Executive summary:

A GLP Ames test was performed in accordance with current OECD, EU, and EPA testing guidelines. The maximum dose level of the test item in the first experiment was selected as the maximum recommended dose level of 5000 μg/plate. There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the first mutation test (plate incorporation method). Consequently, the same maximum dose level was used as the maximum concentration in the second mutation test. Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the second mutation test (pre-incubation method). No test item precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix. There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic

activation (S9-mix) in Experiment 1 (plate incorporation method). Similarly, no significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 2 (pre-incubation method). The positive controls were functional.