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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This study was selected as the key study because the information provided for the hazard endpoint is sufficient for the purpose of classification and labeling and/or risk assessment. The assay was conducted prior of the 1997 adaptation of the OECD 471, and was conducted with up to a 25-fold higher top dose concentration than recommended by OECD. It was also conducted with a battery of tester strains that included only TA 1535 and TA 1537 of the currently recommended five tester strains. However, strains TA 98 and TA 1538, and TA 100 and TA 1535 are isogenic. Considering this, and the high dose levels used, it is highly unlikely that the use of strains TA 98 and TA 100 would have changed the outcome of the assay. Furthermore, the assay did not include an E.coli WP2 or S. typhimurium TA 102 tester strain. These strains are known to specifically detect certain oxidizing mutagens, cross-linking agents and hydrazines other Salmonella tester strains may not be sensitive to. Based on the physico-chemical characteristics of the test substance, the inclusion of any of these strains would not have changed the outcome of the Ames assay.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1978
Report Date:
1978

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
yes
Remarks:
3 strains of bacterial used
GLP compliance:
not specified
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Purity: not reported

Method

Target gene:
histidine
Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535
Species / strain / cell type:
S. typhimurium TA 1537
Species / strain / cell type:
S. typhimurium TA 1538
Metabolic activation:
with and without
Metabolic activation system:
S-9
Test concentrations with justification for top dose:
0, 15.6, 31.25, 62.5 and 125 mg/plate.
Vehicle / solvent:
dissolved in phosphate buffered saline
Controls
Untreated negative controls:
not specified
Negative solvent / vehicle controls:
not specified
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
3-methylcholanthrene
Details on test system and experimental conditions:
NUMBER OF REPLICATIONS: 4
Statistics:
The statistical analysis according to KAPLAN has previously been described.

Results and discussion

Test resultsopen allclose all
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
not specified
Untreated negative controls validity:
not specified
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
not specified
Untreated negative controls validity:
not specified
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1538
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
not specified
Untreated negative controls validity:
not specified
Positive controls validity:
valid

Any other information on results incl. tables

Only in the first experiment, with the highest dose of the compound added to the bacteria and only after metabolic activation a significant (p< 0.01), about twofold increase of the revertants above background could be observed with Salmonella typhimurium TA 1538. As usually in the AMES test only three times more revertant colonies as compared to the background are considered to be a positive result and as this observation could not be reproduced, we do not think this finding to be of great relevance. Moreover, even in an experiment with 10 plates per dosage group. The result could not be reproduced, while with the positive control 3-MCA a 15-fold increase of the revertant colonies above background could be observed.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative

This study and the conclusions which are drawn from it fulfill the quality criteria (validity, reliability, repeatability).
Ames test is negative.
Executive summary:

The Ames test with Salmonella typhimurium TA 1535, TA 1537 and TA 1538 was carried out to assess the potential mutagenic activity of the test substance. Only in the first experiment, with the highest dose of the compound added to the bacteria and only after metabolic activation a significant (p< 0.01), about twofold increase of the revertants above background could be observed with Salmonella typhimurium TA 1538. Although this increase is statistically significant, it is very likely to be an artefact due to the biological variation of the system, as the effect could not be reproduced in further experiments and as usually only a threefold increase of revertant colonies above background or more is considered to be positive.

Neither the test substance nor one of its metabolites formed by a rat liver microsomal fraction was able to induce gene mutations.