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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 21 JUL 1992 to 4 SEP 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study (OECD 471) with acceptable restrictions (not all proposed strains tested)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992
Report Date:
1992

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
yes
Remarks:
: proposed strains E.coli WP2 uvrA or S.typhimurium TA102 not tested
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Method

Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Additional strain / cell type characteristics:
not specified
Species / strain / cell type:
S. typhimurium TA 1538
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
S9 liver homogenate from Aroclor 1254 induced Sprague-Dawley rats
Test concentrations with justification for top dose:
100, 333, 667, 1000, 3330, 5000 µg/plate
Vehicle / solvent:
- Vehicle/solvent used: DMSO
Controls
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: without metabolic activation: sodium azide (TA100, TA1535); 2-nitrofluorene (TA98, TA1538); ICR-191 (TA1537); with metabolic activation: 2-aminoanthracene (TA98, TA100, TA1535, TA1537, TA1538)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

A dose rangefinding study was performed using tester strain TA100 both in the presence and absence of S9 mix. Ten doses of test article were tested at one plate per dose. The test article was checked for cytotoxicity up to a maximum concentration of 5000 µg/plate.

The tester strains were exposed to the test article via the plate incorporation methodology originally described by Ames et al (1975) and Maron and Ames (1983). All doses of the test article, the vehicle controls and the positive controls were plated in triplicate.
The S9 mix and dilutions of the test article were prepared immediately prior to their use.
When S9 mix was not required, 100 µl of tester strain and 100 µl of vehicle or test article dose was added to 2.5 ml of molten selective top agar (maintained at 45 ± 2°C). When S9 mix was required, 500 µl of S9 mix, 100 µl of tester strain and 100 ml of vehicle or test article dose was added to 2.0 ml of molten selective top agar. After the required components had been added, the mixture was vortexed and overlaid onto the surface of 25 ml of minimal bottom agar contained in a 15 x 100 mm petri dish. After the overlay had solidified, the plates were inverted and incubated for 48 ± 8 hr at 37 ± 2°C. Positive control articles were plated using a 50 µl plating aliquot.


DURATION
- Exposure duration: 48 +/- 8 h

DETERMINATION OF CYTOTOXICITY
- Method: other: decrease in the number of revertant colonies per plate and/or by a thinning or disappearance of the bacterial background lawn.
Evaluation criteria:
For a test article to be considered positive, it must produce at least a 2-fold increase in the mean revertants per plate of at least one of these tester strains over the mean revertants per plate of the appropriate vehicle control. This increase in the mean number of revertants per plate must be accompanied by a dose response to increasing concentrations of the test article.
Tester Strains TA1535, TA1537 and TA1538
For a test article to be considered positive, it must produce at least a 3-fold increase in the mean revertants per plate of at least one of these tester strains over the mean revertants per plate of the appropriate vehicle control. This increase in the mean number of revertants per plate must be accompanied by a dose response to increasing concentrations of the test article.
Statistics:
no data

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:
no cytotoxicity
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:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Additional information on results:
- Precipitation: the test item formed a suspension in DMSO in the stock solution and all dilutions tested and precipitated at the highest concentration tested (5000 µg/plate)

RANGE-FINDING/SCREENING STUDIES:
The dose rangefinding study was conducted on the test article using tester strain TA100 in both the presence and absence of S9 (one plate per dose). Ten doses of test article, from 5,000 to 6.67 µg were tested. No cytotoxicity was observed in either the presence or absence of S9 as evidenced by no observed decrease in the number of revertants per plate. The bacterial background lawn was evaluated as normal up to the 1,000 pg per plate dose in both the presence and absence of S9. The lawns on the plates above this dose could not be evaluated due to the presence of test article precipitate.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Any other information on results incl. tables

The results of the initial assay were confirmed by an independent confirmatory assay.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative with metabolic activation
negative without metabolic activation

The test item (91235) did not exert mutagenic activity in the reverse bacterial mutation assay (plate incorporation assay) with and without metabolic activation.

Executive summary:

Mutagenic activity of the test item was investigated in Salmonella typhimurium strains TA 1535, TA 1537, TA98 and TA100 with (induced rat liver S9 mix) and without metabolic activation at concentrations of 100, 333, 667, 1000, 3330 and 5000 µg/plate using the plate incorporation assay. The test item did not reveal any mutagenic activity under the conditions tested. The appropriate reference mutagenes showed distinct positive mutagenic effects.