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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:
from 2001-04-27 till 2001-05-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report date:
2001

Materials and methods

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

Test material

Constituent 1
Reference substance name:
Ammonium thiosulphate
EC Number:
231-982-0
EC Name:
Ammonium thiosulphate
Cas Number:
7783-18-8
IUPAC Name:
diammonium thiosulfate
Constituent 2
Reference substance name:
ammonium thiosulfate
IUPAC Name:
ammonium thiosulfate
Details on test material:
- Name of test material (as cited in study report): Ammonium Thiosulfate
- Substance type: pure active substance
- Physical state: liquid, clear colourless
- Storage condition of test material: at room temperature, protected from light

Method

Target gene:
not applicable
Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
E. coli WP2 uvr A
Metabolic activation:
with and without
Metabolic activation system:
S9-mix
Test concentrations with justification for top dose:
75, 200, 600, 1800 and 5000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: sterile distilled water
- Justification for choice of solvent/vehicle: A solubility test was conducted to select the vehicle.
Controlsopen allclose all
Untreated negative controls:
yes
Remarks:
Sterility control: the highest dose level was plated on selective agar. The plates were incubated under the same conditions as the test plates.
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene; 1.0 and 10 µg/plate
Remarks:
with metabolic activation; all S. typhimurium strains and E.coli
Untreated negative controls:
yes
Remarks:
Sterility control: the highest dose level was plated on selective agar. The plates were incubated under the same conditions as the test plates.
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
2-nitrofluorene
Remarks:
without metabolic activation; strain TA 98

Migrated to IUCLID6: 1.0 µg/plate
Untreated negative controls:
yes
Remarks:
Sterility control: the highest dose level was plated on selective agar. The plates were incubated under the same conditions as the test plates.
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
without metabolic activation; strains TA 100 and TA 1535

Migrated to IUCLID6: 1.0 µg/plate
Untreated negative controls:
yes
Remarks:
Sterility control: the highest dose level was plated on selective agar. The plates were incubated under the same conditions as the test plates.
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
Remarks:
without metabolic activation; strain TA 1537

Migrated to IUCLID6: 75 µg/plate
Untreated negative controls:
yes
Remarks:
Sterility control: the highest dose level was plated on selective agar. The plates were incubated under the same conditions as the test plates.
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
without metabolic activation; E.coli WP2 uvrA

Migrated to IUCLID6: 1000 µg/plate
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: 48 hours at 37°C

NUMBER OF REPLICATIONS: tested in triplicate

EVALUATION: Revertant colonies for a given tester strain and activation condition, except for positive controls, were counted either entirely by automated colony counter er entirely by hand unless the plate exhibited toxicity.

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth (bacterial background lawn):
The initial toxicity-mutation assay was used to establish the dose range over which the test article would be assayed and to provide a preliminary mutagenicity evaluation. Vehicle controls, positive controls and 8 dose levels (2.5, 7.5, 25, 75, 200, 600, 1800 and 5000 µg/plate) of the test item were plated, two plates per dose, with overnight cultures of TA 98, TA 100, TA 1535, TA 1537 and WP2 uvrA on selective minimal agar in the presence and absence of metabolic activation system.
Evaluation criteria:
For the test item to be evaluated positive, it must cause a dose-related increase in the mean revertants per plate of at least one tester strain over a minimum of two increasing concentrations of test article. Data sets for tester strains TA 1535 and TA 1537 were judged positive if the increase in the mean revertants at the peak of the dose response is equal to or greater than three times the mean vehicle control value. Data sets for tester strains TA 98, TA 100 and WP2 uvrA were judged positive if the increase in the mean revertants at the peak of the dose response is equal to or greater than two times the mean vehicle control value.
Statistics:
For each replicate plating, the mean and standard deviation of the number of revertants per plate were calculated and reported.

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
Remarks:
No positive responses were observed with any of the tester strains at any tested dose level.
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Remarks:
Neither precipitation nor appreciable toxicity was observed.
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
Remarks:
No positive responses were observed at any tested dose level.
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Remarks:
Neither precipitation nor appreciable toxicity was observed.
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
- Water solubility: Water was selected as the solvent of choice based on compatibility with the target cells and solubility of the test article. The test article was soluble and clear in water at approximately 50 mg/mL, the maximum concentration tested.
- Precipitation: Precipitate was evaluated by visual examination without magnification. Toxicity and degree of precipitation were scored relative to the vehicle control plate. Plates with sufficient test item precipitate to interfere with automated colony counting were counted manually.
- Other confounding effects:

RANGE-FINDING/SCREENING STUDIES: In the initial toxicity-mutation assay, the maximum dose tested was 5000 µg/plate. Neither precipitation nor appreciable toxocity was observed. Based on the findings of the toxicity assay, the maximum dose plated in the mutagenicity assay was 5000 µg/plate.

COMPARISON WITH HISTORICAL CONTROL DATA: Historical negative and positive control values (1998-2000) are available.

ADDITIONAL INFORMATION ON CYTOTOXICITY: No further details.
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

Under the conditions of this study, the test item Ammonium thiosulfate was concluded to be negative in the Bacterial Reverse Mutation Assay.
Executive summary:

The test item, Ammonium thiosulfate, was tested in the Bacterial Reverse Mutation Assay using S. Typhimurium tester strains TA 98, TA 100, TA 1535 and TA 1537 and Escherichia coli strain WP2 uvrA in the presence and absence of metabolic activation system. The assay was performed in two phases, using the plate incorporation method. The first phase, the initila toxicity-mutation assay was used to establish the dose-range for the mutagenicity assay and to provide a preliminary mutagenicity evaluation. The second phase, the mutagenicity assay, was used to evaluate and confirm the mutagenic potential of the test article.

In the initial toxicity-mutation assay, the maximum dose tested was 5000 µg/plate. Dose levels tested were 2.5, 7.5, 25, 75, 200, 600, 1800 and 5000 µg/plate. In the initial toxicity-mutation assay, no positive response was observed. Neither precipitate nor appreciable toxicity was observed. Based on the findings of the toxicity-mutation assay, the maximum dose plated in the mutagenicity assay was 5000 µg/plate. In the confirmatory mutagenicity assay, no positive response was observed.