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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:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
15th March to 3rd April 2002.
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study conducted under GLP. Used as read-across to dibutyltin maleate to dibutyltin methyl maleate.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
yes
Qualifier:
according to
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Deviations:
yes
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Method

Target gene:
Histidine requirement in the Salmonella typhimurium strains and histidine requirement in the Escherichia coli strain.
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):
- Type and identity of media: Nutrient broth supplemented with 7.4% dimethyl sulfoxide (DMSO) at <60°C
- Properly maintained: yes
- Periodically checked for karyotype stability: yes
- Periodically "cleansed" against high spontaneous background: yes
Additional strain / cell type characteristics:
not specified
Species / strain / cell type:
E. coli WP2 uvr A
Details on mammalian cell type (if applicable):
- Type and identity of media:
- Properly maintained: yes/no
- Periodically checked for Mycoplasma contamination: yes/no
- Periodically checked for karyotype stability: yes/no
- Periodically "cleansed" against high spontaneous background: yes/no
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
S-9 activation system
Test concentrations with justification for top dose:
0.3, 0.8, 2.3, 7, 21 and 62 µg/plate.
The actual concentrations of the test substance in the test solutions were not determined. Therefore, the concentrations quoted are nominal concentrations.
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Methanol
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
other: Various for each Strain, see table 1
Details on test system and experimental conditions:
METHOD OF APPLICATION: In agar (plate incorporation)

DURATION
- Preincubation period: For each test, fresh cultures were prepared by inoculating nutrient broth with a thawed aliquot of the stock culture in question and incubating the broth for approximately 10-16 h at c. 37 °C while shaking.
- Exposure duration: The plates were incubated at ca. 37 °C for 48-72 hours.

DETERMINATION OF CYTOTOXICITY
- Method: Cytotoxicity is defined as a reduction in the number of revertant colonies and/or a clearing of the background lawn of bacterial growth.
Evaluation criteria:
The mutagenicity study is considered valid if the mean colony counts of the control values of the strains are within acceptable ranges, if the results of the positive controls meet the criteria for a positive response, and if no more than 5 % of the plates are lost through contamination or other unforeseen events.

A test substance is considered to be positive in the bacterial gene mutation test if the mean number of revertant colonies on the test plates is concentration-related increased or if a reproducible two-fold or more increase is observed compared to that on the negative control plates.

A test substance is considered to be negative in the bacterial gene mutation test if it produces neither a dose-related increase in the mean number of revertant colonies nor a reproducible positive response at any of the test points.

In case of an inconclusive first assay, a second independent assay was conducted. The first mutagenicity assay is regarded inconclusive if a positive or equivocal response at only one concentration is observed or if a positive or equivocal responses at several concentrations without a concentration-related increase are observed.

Omission of the second assay under these conditions is acceptable as a single assay does not or hardly results in false negative conclusions (TNO historical data and Kirkland and Dean, 1994).

Positive results from the bacterial reverse mutation test indicate that a substance induces point mutations by base substitutions or frameshifts in the genome of either Salmonella typhimurium and/or Escheria coli. Negative results indicate that under the test conditions, the test substance is not mutagenic in the tested strains.
Statistics:
No statistical analysis was performed.
Both numerical significance and biological relevance are considered together in the evaluation.
Historical data on the bacterial reverse mutation tests, including data on positive and negative controls, are given.

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:
cytotoxicity
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:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
RANGE-FINDING/SCREENING STUDIES:
A dose range finding test was performed with TA98 in both the absence and the presence of S9-mix with ten different concentrations of the test substance, ranging from 0.3 - 5000 µg/plate. 2,2-Dibutyl-1,3,2-dioxastannepin-4,7-dione (dibutyltin maleate) was toxic at 21 - 5000 µg/plate in the absence of S9 mix and at 62 - 5000 µg/plate in the presence of S9-mix, as was evidenced by a decrease in the mean number of revertant colonies.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Any other information on results incl. tables

2,2-Dibutyl-1,3,2-dioxastannepin-4,7-dione (dibutyltin maleate) was toxic to all strains at the highest concentration both in the absence and presence of S9-mix, as was evidenced by a decrease in the mean number of revertant colonies. The test substance was also toxic to all Salmonella typhimurium strains at 21 µg/plate (except for TA1537 and TA98 in the absence of S9-mix). In addition, the test substance was toxic to TA1535 in the absence S9-mix and to TA1537 in the presence of S9-mix at 7 µg/plate. However, at least three concentrations were left to evaluate the mutagenicity of the test substance.

In both the absence and the presence of S9-mix and in all strains, 2,2-dibutyl-1,3,2-dioxastannepin-4,7-dione (dibutyltin maleate) did not cause a more than two-fold or a dose-related increase in the mean number of revertant colonies appearing in the test plates compared to the background spontaneous reversion rate observed with the negative control.

The mean number of his + and trp+ revertant colonies of the negative controls were within the acceptable range, and the positive controls gave the expected increase in the mean number of revertant colonies.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative

It is concluded that the results obtained with the test substance in Salmonella typhimurium strains TA 1535, TA 1537, TA 98 and TA 100, and in the Escherichia coli strain WP2 uvrA, in both the absence and the presence of the S9-mix, indicate that 2,2-dibutyl-1,3,2-dioxastannepin-4,7-dione (dibutyltin maleate) was not mutagenic under the conditions employed in this study.
Executive summary:

In a Bacterial reverse mutation test, the results the results obtained with the test substance in Salmonella typhimurium strains TA 1535, TA 1537, TA 98 and TA 100, and in the Escherichia coli strain WP2 uvrA, in both the absence and the presence of the S9-mix, indicate that 2,2-dibutyl-1,3,2-dioxastannepin-4,7-dione (dibutyltin maleate) was not mutagenic under the conditions employed in this study.

2,2-Dibutyl-1,3,2-dioxastannepin-4,7-dione (dibutyltin maleate) was toxic to all strains at the highest concentration both in the absence and presence of S9-mix, as was evidenced by a decrease in the mean number of revertant colonies.

The study was conducted to the OECD Guideline no. 471.