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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:
11 April 1990 - 19 July 1990
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
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. Percentage of DMTC is only 72%. 28% is MMTC.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report Date:
1990

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline
Details on test material:
- Name of test material (as cited in study report): Dimethyltin Dichloride [CAS No. 753-73-1]:Methyltin Trichloride [CAS No. 993-16-8] (72:28% mixture)

Method

Target gene:
Histidine
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: histidine auxotrophs
Species / strain / cell type:
S. typhimurium TA 1538
Additional strain / cell type characteristics:
other: histidine auxotrophs
Metabolic activation:
with and without
Metabolic activation system:
Aroclor 1254-induced rat liver S-9
Test concentrations with justification for top dose:
Range finding assay: 10, 50, 100, 500, 1000, and 5000 µg/plate
First mutagenicity assay: 10, 50, 100, 500, 1000, and 5000 µg/plate
Second mutagenicity assay: 5, 10, 50, 100, 500, and 1000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Deionized water for the test material; DMSO for the positive control substances.
Controlsopen allclose all
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
Remarks:
Migrated to IUCLID6: hydrochloride. 50 µg/plate for frameshift mutant TA1537
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
Migrated to IUCLID6: 5 µg/plate for the base-pair substitution mutants TA1535 and TA100
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
2-nitrofluorene
Remarks:
Migrated to IUCLID6: 50 µg/plate for the frameshift mutants TA1538 and TA98
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-Anthramine: 2 ug/plate for strains TA1538, TA98, and TA100 and at 4 ug/plate for strains TA1535 and TA1537 in the presence of metabolic activation are used to ensure the efficacy of the activation system.
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Preincubation period: The cultures are allowed to sit unshaken for 2 to 4 hours, then gently shaken (100 rpm) for 11 to 14 hours at 37 °C.
- Exposure duration: After the top agar has set, the plates are incubated at 37°C for about 48 hours.
- Expression time (cells in growth medium): set, the plates are incubated at 37°C for about 48 hours. The histidine-independent revertant colonies are counted following the incubation period; however, if the plates cannot be immediately evaluated, they are refrigerated at 4°C until they can be counted.

NUMBER OF REPLICATIONS: with three plates per dose level, both with and without a mammalian liver metabolic activation.

NUMBER OF CELLS EVALUATED: 10^8

DETERMINATION OF CYTOTOXICITY
Toxicity is evidenced by several phenomena: a substantial decrease in the number of revertant colonies on the test plates compared with the controls, the clearing or absence of the background lawn growth, or the formation of pinpoint nonrevertant colonies.
Evaluation criteria:
The histidine-independent revertant colonies are counted using an automated colony counter. When accurate counts cannot be obtained (e.g., because of precipitation on the plates), the colonies are counted manually using an electric probe colony counter. The actual numbers of revertant colonies observed and the condition of the background lawn growth are presented in the attached tables. No designation or "-7" indicates a normal background lawn. Toxicity is designated by "-5" for background lawn thinning, "-4" for pinpoint colonies, and "-3" for absence of bacterial growth.

CRITERIA FOR INTERPRETATION
Positive - A test material is considered a mutagen when it induces a reproducible, dose-related increase in the number of revertants in one or more strains. This increase should occur for at least three consecutive dose levels.

Negative - A test material is considered a nonmutagen when no dose-related increase in the number of revertants is observed in at least two independent experiments.

Inconclusive - When a test material cannot be identified clearly as a mutagen or nonmutagen, the results are classified as inconclusive.
Statistics:
The results are a tabulation of the number of colonies appearing on the plates. Mean and standard deviation values were, determined for the number of revertants at each dose level.

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
Remarks:
≥ 1000 µg/plate
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1538
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
1000 µg/plate
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Additional information on results:
The Ames Salmonella/microsome assay was used to evaluate the ability of mixes of methyltin compounds to induce genetic damage in S. typhimurium strains TA1535, TA1537, TA1538, TA98, and TA100. The assays were performed using the standard plate incorporation procedure, in both the presence and absence of a rat liver metabolic activation system. The presence of the appropriate genetic characteristics was verified for the strains used in this study. The results of the controls were acceptable for all assays.

We conducted the preliminary assay with tester strain TA100 in the presence and absence of metabolic activation containing 4% S-9. The doses used were 10, 50, 100, 500, 1000, and 5000 µg/plate. Toxicity was indicated with revertant counts below the spontaneous background level at the 1000 µg dose and thinning of the background lawn at 5000 µg, both in the presence and absence of metabolic activation. Based on these results, the first assay was conducted at the same dose levels, with all five tester strains, in the presence and absence of 4% S-9. There was no evidence of a dose-related increase in the number of histidine revertants with any tester strain. Toxicity was noted with all tester strains at 5000 µg as background lawn thinning or complete absence of bacterial growth. Some toxicity was also noted at 1000 µg. The second assay was conducted at dose levels of 5, 10, 50, 100, 500, and 1000 µg/plate, and the .percent of S-9 in the metabolic activation mixture was increased to 10% due to the lack of response in the first assay. Again, there was no dose-related increase in the number of histidine revertants with any tester strain. Toxicity was observed at the 1000 µg dose with some strains, indicated by a decrease in the number of revertant colonies below background levels.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative

Mixes of methyltin compounds were not mutagenic when tested according to the procedures used in this assay.
Executive summary:

Mixes of Methyltin Compounds were examined for mutagenic activity in the Salmonella/microsome assay using the standard plate incorporation procedure with Salmonella typhimurium strains TA1535, TA1537, TA1538, TA98 and TA100, in both the presence and absence of an Aroclor 1254-induced rat-liver metabolic activation system. No reproducible, dose-related increase in the number of histidine revertant colonies was observed with any tester strain. Therefore, mixes of methyltin compounds were not mutagenic when tested according to the procedures used in this assay.