2,2-bis(methylthio)propane

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

No chemical analysis of the dosage forms was performed as part of this study.

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

478-900-1

EC Name:

-

Cas Number:

6156-18-9

Molecular formula:

C5 H12 S2

IUPAC Name:

2,2-bis(methylthio)propane

Details on test material:

- Name of test material (as cited in study report): BISMETHYLTHIOPROPANE
- Synonym: BMTP
- Chemical name: 2,2-bis-methylthiopropane
- Batch number: 2KS149
- Description: colorless liquid
- Storage conditions: at room temperature and protected from light
- Purity: 97.76%
- Date of analysis: 8 November 2006
- Expiry date: November 2007.

Method

Target gene:

Histidine operon

Species / strain

Species / strain / cell type:

S. typhimurium, other: 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Metabolic activation system:

liver post mitochondrial fraction (S9 fraction) of rats induced with Aroclor 1254

Test concentrations with justification for top dose:

21, 62, 185, 556, 1667 and 5000 µg/plate, for all tester strains with and without S9 mix

Vehicle / solvent:

dimethyl sulfoxide

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: see below

Details on test system and experimental conditions:

DURATION
- Preincubation period: 60 min
- Exposure duration: 48 to 72 hours

NUMBER OF REPLICATIONS: 2

DETERMINATION OF CYTOTOXICITY
- Method: The evaluation of the toxicity was performed on the basis of the observation of the decrease in the number of revertant colonies and/or a thinning of the bacterial lawn.

Evaluation criteria:

A reproducible 2-fold increase (for the TA 98, TA 100 and TA 102 strains) or 3-fold increase (for the TA 1535 and TA 1537 strains) in the number of revertants compared with the vehicle controls, in any strain at any dose-level and/or evidence of a dose-relationship was considered as a positive result. Reference to historical data, or other considerations of biological relevance may also be taken into account in the evaluation of the data obtained.

Statistics:

Not applicable

Results and discussion

Test results

Species / strain:

S. typhimurium, other: 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

PRELIMINARY TOXICITY TEST
The test item was freely soluble in the vehicle (DMSO) at 100 mg/mL.
Consequently, with a treatment volume of 50 µL/plate, the dose-levels were 10, 100, 500, 1000, 2500 and 5000 µg/plate.
No precipitate was observed in the Petri plates when scoring the revertants at any dose-level.
A moderate to strong toxicity (mainly thinning of the bacterial lawn) was noted towards the three strains used, either with or without S9 mix at dose-levels = 1000 µg/plate.

MUTAGENICITY EXPERIMENTS
No precipitate was observed in the Petri plates when scoring the revertants at any dose-level.
Without S9 mix, a moderate to strong toxicity was noted at dose-levels = 556 µg/plate.
With S9 mix, a moderate to strong toxicity was noted at 5000 µg/plate in the direct plate incorporation method and at dose-levels = 185 µg/plate in the preincubation method.
The test item did not induce any noteworthy increase in the number of revertants, either with or without S9 mix, in any of the five strains in the first experiment.

Applicant's summary and conclusion

Conclusions:

2,2-BIS(METHYLTHIO)PROPANE did not show any mutagenic activity in the bacterial reverse mutation test with Salmonella typhimurium.

Executive summary:

The potential of 2,2-BIS(METHYLTHIO)PROPANE (BMTP) to induce reverse mutation was evaluated in Salmonella typhimurium. The study was performed according to the OECD guideline 471 and in compliance with the Principles of Good Laboratory Practice Regulations. A preliminary toxicity test was performed to define the dose-levels of BMTP to be used for the mutagenicity study. BMTP was then tested in two independent experiments, with and without a metabolic activation system, the S9 mix, prepared from a liver post-mitochondrial fraction (S9 fraction) of rats induced with Aroclor 1254. Both experiments were performed according to the direct plate incorporation method except for the second test with S9 mix, which was performed according to the preincubation method (60 minutes,). Five strains of bacteria Salmonella typhimurium: TA 1535, TA 1537, TA 98, TA 100 and TA 102 were used. Each strain was exposed to at least five dose-levels of the test item (three plates/dose-level). After 48 to 72 hours of incubation at, the revertant colonies were scored. The evaluation of the toxicity was performed on the basis of the observation of the decrease in the number of revertant colonies and/or a thinning of the bacterial lawn. BMTP was dissolved in dimethylsulfoxide (DMSO). Since BMTP was freely soluble and not severely toxic in the preliminary test, the highest dose-level for the main test was 5000 µg/plate, according to the criteria specified in the international guidelines. The selected treatment-levels ranged from 21 to 5000 µg/plate, for all tester strains with and without S9 mix. No precipitate was observed in the Petri plates when scoring the revertants at any dose-level. Without S9 mix, a moderate to strong toxicity was noted at dose-levels = 556 µg/plate. With S9 mix, a moderate to strong toxicity was noted at 5000 µg/plate in the direct plate incorporation method and at dose-levels = 185 µg/plate in the preincubation method. BMTP did not induce any noteworthy increase in the number of revertants, either with or without S9 mix, in any of the five strains in the first experiment. The number of revertants for the vehicle and positive controls was as specified in the acceptance criteria. The study was therefore considered valid. 2,2-BIS(METHYLTHIO)PROPANE did not show any mutagenic activity in the bacterial reverse mutation test with Salmonella typhimurium.