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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:
From March 10, 2004 to March 26, 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report Date:
2004

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
liquid: viscous
Details on test material:
PARAD substance 139
Specific details on test material used for the study:
- Name: PARAD Substance 139.
- Batch: 31104251.
- Molecular formula: C6H10O3.xH3O4P.
- Molecular weight: ~250.
- CAS number: 52628-03-2.
- Description: Slightly yellowish viscous liquid.
- Purity: Not available (mixture).
- Storage: At room temperature in the dark.
- Stability under storage conditions: Stable.
- Expiry date: December 31, 2004.

Method

Target gene:
TA1537: hisC3076
TA98: hisD3052
TA1535: hisG46
TA100: hisG46
Species / strain
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Details on mammalian cell type (if applicable):
The Salmonella typhimurium strains were regularly checked to confirm their histidine requirement, crystal violet sensitivity, ampicillin resistance (TA98 and TA100), UV-sensitivity and the number of spontaneous revertants.

The Escherichia coli WP2uvrA strain detects base-pair substitutions. The strain lacks an excision repair system and is sensitive to agents such as UV. The sensitivity of the strain to a wide variety of mutagens has been enhanced by permeabilization of the strain using Tris-EDTA treatment (ref.1). The strain was regularly checked to confirm the tryptophan-requirement, UV sensitivity and the number of spontaneous revertants. Stock cultures of the five strains were stored in liquid nitrogen (-196°C).
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
Rat liver homogenate S9 fraction
Test concentrations with justification for top dose:
Dose range finding test: 3, 10, 33, 100, 333, 1,000, 3,330 and 5,000 μg/plate
Mutation test:
Experiment I: 3, 10, 33, 100, 333, 1,000, 3,330 and 5,000 μg/plate
Experiment II: 100, 333, 1,000, 3,330 and 5,000 μg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Dimethyl sulfoxide
- Stability in vehicle: Stable
Controlsopen allclose all
Untreated negative controls:
yes
Remarks:
DMSO
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Remarks:
TA98, TA100, TA1535, TA1537, WP2uvrA
Positive control substance:
other: 2-aminoanthracene
Remarks:
With metabolic activation (+S9 mix)
Untreated negative controls:
yes
Remarks:
DMSO
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Remarks:
TA1535
Positive control substance:
sodium azide
Remarks:
Without metabolic activation (-S9 mix)
Untreated negative controls:
yes
Remarks:
DMSO
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Remarks:
TA1537
Positive control substance:
9-aminoacridine
Remarks:
Without metabolic activation (-S9 mix)
Untreated negative controls:
yes
Remarks:
DMSO
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Remarks:
TA98
Positive control substance:
other: daunomycin
Remarks:
Without metabolic activation (-S9 mix)
Untreated negative controls:
yes
Remarks:
DMSO
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Remarks:
TA100
Positive control substance:
methylmethanesulfonate
Remarks:
Without metabolic activation (-S9 mix)
Untreated negative controls:
yes
Remarks:
DMSO
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Remarks:
WP2uvrA
Positive control substance:
4-nitroquinoline-N-oxide
Remarks:
Without metabolic activation (-S9 mix)
Details on test system and experimental conditions:
Cell culture:
Preparation of bacterial cultures:
Samples of frozen stock cultures of bacteria were transferred into enriched nutrient broth and incubated in a shaking incubator (37°C, 150 spm), until the cultures reached an optical density of 1.0±0.1 at 700 nm (10^9 cells/mL). Freshly grown cultures of each strain were used for a test.

Agar plates:
Agar plates (9 cm) contained 25 mL glucose agar medium. Glucose agar medium contained per liter: 18 g purified agar in Vogel-Bonner Medium E, 20 g glucose. The agar plates for the test with the Salmonella typhimurium strains also contained 12.5 μg/plate biotin and 15 μg/plate histidine and the agar plates for the test with the Escherichia coli strain contained 15 μg/plate tryptophan.

Top agar:
Milli-Q water containing 0.6% (w/v) bacteriological agar and 0.5% (w/v) sodium chloride was heated to dissolve the agar. Samples of 3 mL top agar were transferred into 10 mL glass tubes with metal caps. Top agar tubes were autoclaved for 20 min at 121±3°C.

Environmental conditions:
All incubations were carried out in the dark at 37±1°C. The temperature was monitored during the experiment.

Dose range finding test:
Selection of an adequate range of doses was based on a dose range finding test with strain TA100 and the WP2uvrA strain, both with and without S9-mix. Eight concentrations, 3, 10, 33, 100, 333, 1,000, 3,330 and 5,000 μg/plate were tested in triplicate. This dose range finding test was reported as a part of the first experiment of the mutation assay. The highest concentration of test substance used in the subsequent mutation assay was 5 mg/plate.

Mutation assay:
At least five different doses (increasing with approximately half-log steps) of the test substance were tested in triplicate in each strain. The test substance was tested both in the absence and presence of S9-mix in each strain, in two independent experiments. Top agar in top agar tubes was molten and heated to 45°C. The following solutions were successively added to 3 mL molten top agar: 0.1 mL of a fresh bacterial culture (10^9 cells/mL) of one of the tester strains, 0.1 mL of a dilution of the test substance in dimethyl sulfoxide and either 0.5 mL S9-mix (in case of activation assays) or 0.5 mL 0.1 M phosphate buffer (in case of non-activation assays). The ingredients were mixed on a Vortex and the content of the top agar tube was poured onto a selective agar plate. After solidification of the top agar, the plates were turned and incubated in the dark at 37±1°C for 48 h. After this period revertant colonies (histidine independent (His+) for Salmonella typhimurium bacteria and tryptophan independent (Trp+) for Escherichia coli) were counted.

Colony counting:
The revertant colonies (histidine independent c.q. tryptophan independent) were counted automatically with a Protos model 50,000 colony counter or manually, if less than 40 colonies per plate were present. Plates with sufficient test article precipitate to interfere with automated colony counting were counted manually.
Evaluation criteria:
Acceptability of the assay:
A Salmonella typhimurium reverse mutation assay and/or Escherichia coli reverse mutation assay is considered acceptable if it meets the following criteria:
a) The negative control data (number of spontaneous revertants per plate) should be within the laboratory background historical range for each tester strain.
b) The positive control chemicals should produce responses in all tester strains, which are within the laboratory historical range documented for each positive control substance. Furthermore, the mean plate count should be at least three times the concurrent vehicle control group mean.
c) The selected dose range should include a clearly toxic concentration or should exhibit limited solubility as demonstrated by the preliminary toxicity range-finding test or should extend to 5 mg/plate.

Data evaluation:
No formal hypothesis testing was done.
A test substance is considered negative (not mutagenic) in the test if:
a) The total number of revertants in any tester strain at any concentration is not greater than two times the solvent control value, with or without metabolic activation.
b) The negative response should be reproducible in at least one independently repeated experiment.

A test substance is considered positive (mutagenic) in the test if:
a) It induces at least a 2-fold, dose related increase in the number of revertants with respect to the number induced by the solvent control in any of the tester strains, either with or without metabolic activation. However, any mean plate count of less than 20 is considered to be not significant.
b) The positive response should be reproducible in at least one independently repeated experiment.
The preceding criteria were not absolute and other modifying factors might enter into the final evaluation decision.

Results and discussion

Test results
Key result
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Dose range finding test:
Precipitate:
The test substance did not precipitate in the top agar. Precipitation of test substance on the plates was not observed at the start or at the end of the incubation period in both tester strains.

Toxicity:
To determine the toxicity of test substance, the reduction of the bacterial background lawn, the increase in the size of the microcolonies and the reduction of the revertant colonies were examined. A reduction in the number of revertants equal to the minimal value of the historical control data range is not considered biologically relevant and, therefore, will not be considered cytotoxic. No reduction of the bacterial background lawn and no biologically relevant decrease in the number of revertants were observed.


Mutation assay:
Based on the results of the dose range finding test, test substance was tested up to concentrations of 5,000 μg/plate in the absence and presence of S9-mix in two mutation assays. The first mutation experiment was performed with the strains TA1535, TA1537 and TA98 and the second mutation experiment was performed with the strains TA1535, TA1537, TA98, TA100 and WP2uvrA. Test substance did not precipitate in the top agar. Precipitation of test substance on the plates was not observed at the start or at the end of the incubation period.

Toxicity:
In both mutation assays, there was no reduction in the bacterial background lawn and no biologically relevant decrease in the number of revertants at any of the concentrations tested in all tester strains in the absence and presence of S9-mix.

Number of revertants:
All bacterial strains showed negative responses over the entire dose range, i.e. no dose-related, two-fold, increase in the number of revertants in two independently repeated experiments. The negative and strain-specific positive control values were within our laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly.
Remarks on result:
other: all strains/cell types tested

Any other information on results incl. tables

The negative and strain-specific control values were within laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly.

Applicant's summary and conclusion

Conclusions:
Under the study conditions, the test substance was not found to be mutagenic either in the presence or absence of metabolic activation.
Executive summary:

A study was conducted to test the mutagenic potential of the test substance in a bacterial reverse mutation assay performed according to OECD Guideline 471 and EU Method B.13/14, in compliance with GLP. The study included a preliminary concentration range finding test, an initial mutation test and a confirmatory mutation test. Based on the results of the dose range finding study, the substance was tested in the first mutation assay at a concentration range of 100 to 5,000 μg/plate in the absence and presence of 5% (v/v) S9-mix in Salmonella typhimurium strains TA 98, TA1535 and TA1537. In the second mutation assay, the substance was tested at the same concentration range in the absence and presence of 10% (v/v) S9-mix in Salmonella typhimurium tester strains TA 98, TA100, TA1535, TA1537 and E. coli strain WP2uvrA. The bacterial background lawn was not reduced at any of the concentrations tested and no decrease in the number of revertants was observed. The test substance did not induce a dose-related, two-fold increase in the number of revertant (His+) colonies in each of the five tester strains in the absence and presence of S9-metabolic activation. These results were confirmed in an independently repeated experiment. The negative and strain-specific control values were within laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly. Based on the findings of the study, it can be concluded that the substance was not mutagenic either in the presence or absence of metabolic activation (Verspeek-Rip CM, 2004).