SDBR

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

4 October - 18 October 1999

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Version / remarks:

29 December 1992

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

424-970-3

EC Name:

-

Cas Number:

166255-23-8

Molecular formula:

C16-H14-O3.C6-H16-O3-Si

IUPAC Name:

Triethoxysilylpropyl Dibenzoyl Resorcinol

Test material form:

solid

Details on test material:

Appearance: light yellow solid lumps (2-3 cm)

Specific details on test material used for the study:

Storage conditions: room temperature

Method

Target gene:

Histindine and tryptophan

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced rat liver S9-homogenate

Test concentrations with justification for top dose:

First assay: 0, 62, 185, 556, 1667 and 5000 µg/ plate.
Second assay: 0, 156, 313, 625, 1250 and 2500 µg/ plate.

Vehicle / solvent:

Solvent: DMSO

Controls

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

sodium azide

benzo(a)pyrene

other: 2-aminoanthracene

Details on test system and experimental conditions:

The Salmonella typhimurium strains were provided by Dr. B.N. Ames (University of California Berkeley, USA).
Two mutagenicity assays were performed. The plate-incorporation method with the histidine-requiring S. typhimurium mutants TA 1535, TA 1537, TA 98 and TZ 100 and the tryptophan-requiring Escherichia coli mutant WP2 uvrA as indicator strain was applied.

To 2 mL molten top agar containing 0.6% agar, 0.5% NaCl and 0.05 mM L-histidine,HCl/0.05 mM biotin, maintained at 46ºC were added subsequently: 0.1 mL of a fully grown culture of the appropriate strain, 0.1 mL of the appropriate test substance solution or of the negative or positive control substance, and 0.5 mL S9-mix for metabolic activation or 0.5 mL sodium phosphate 100 mM (pH 7.4) for without metabolic activation. The ingredients were thoroughly mixed and the mix was immediately poured onto minimal glucose agar plates (1.5% agar in Vogel and Bonner medium E with 2% glucose). All determinations were made in triplicate. The plates were incubated at ca. 37ºC for three days. Subsequently, the his+ revertants were observed. Cytotoxicity was defined as a reduction in the number of revertant colonies and/or a clearing of the background lawn of bacterial growth.

Rationale for test conditions:

A preliminary test to assess the toxicity of the test substance to the bacteria was not performed, as no cytotoxicity was expected. Instead, the toxicity test was incorporated into the first mutagenicity assay.

Evaluation criteria:

A response is considered to be positive if the mean number of revertant colonies on the test plate was increased two-fold or more compared to that on the vehicle control.
A test substance is considered to be mutagenic if a concentration-related increase or if a positive response reproducible in two independent assays is observed.
A test substance is considered to be not mutagenic in the bacterial gene mutation test if it produces neither a dose-related increase in the mean number if revertant colonies nor a reproducible positive response at any of the test points.

Historical data on the bacterial reverse mutation test (including positive and negative controls) are included in the report.

Statistics:

Not performed.

Results and discussion

Test results

Test results 1

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 2

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 3

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 4

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Detailed results are attached below.
After addition of the test substance to the plates a white precipitation was observed, especially at the highest concentrations.
SDBR was slightly toxic to the TA 1535 and TA 98 strains in the absence of S9 at the highest concentration tested (5000 µg/plate) as evidenced by a decrease in the mean number of revertant colonies.

Applicant's summary and conclusion

Conclusions:

The results of an Ames study performed according to EC guidelines (with and without metabolic activation) did not indicate mutagenic properties of SDBR.