Disodium metasilicate

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in mammalian cells

Remarks:

Type of genotoxicity: gene mutation

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: according to OECD 476

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Test guideline 2

Guideline:

EU Method B.17 (Mutagenicity - In Vitro Mammalian Cell Gene Mutation Test)

Test guideline 3

Guideline:

EPA OPPTS 870.5300 - In vitro Mammalian Cell Gene Mutation Test

Test guideline 4

Guideline:

other: Japanese Guidelines: Kanpoan No. 287, Environment Protection Agency; Eisei No. 127, Ministry of Health and Welfare; Heisei 09/10/31 Kikyoku No. 2, Ministry of International Trade and Industry

Principles of method if other than guideline:

first experiment 4 hours treatment with and without metabolic activation
second experiment 24 hours treatment without metabolic activation and 4 hours treatment with metabolic activation

GLP compliance:

yes (incl. QA statement)

Remarks:

Harlan Cytotest Cell Research GmbH

Type of assay:

mammalian cell gene mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

C-SAT 080094

IUPAC Name:

C-SAT 080094

Constituent 2

Reference substance name:

Silicic acid, sodium salt

EC Number:

215-687-4

EC Name:

Silicic acid, sodium salt

Cas Number:

1344-09-8

Molecular formula:

Na2O x (SiO2)n with Molar Ratio (MR) (SiO2/Na2O): 1.5 – 4

IUPAC Name:

Silicic acid, sodium salt

Details on test material:

Identity: C-SAT 080094; Sodium silicate solution (weight ratio 3.35)
Tradename: Natronwasserglas 37/40PE (Sodium Silicate 37/40PE, aqueous Sodium
Silicate Solution WR 3.35)
Batch No.: 248908210
Molecular Weight: 263 g/mol
Purity: 36% active ingredient, 64% water
Stability in Solvent: Not indicated by the sponsor
Storage: At room temperature
Expiration Date: September 10, 2009

On the day of the experiment (immediately before treatment), the test item was dissolved in deionised water.
The final concentration of deionised water in the culture medium was 10 % v/v.
In the pre-experiment the pH at the three highest concentrations was adjusted with 2N hydrochloric acid.

Method

Target gene:

HPRT

Species / strain

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Details on mammalian cell type (if applicable):

- Type and identity of media: MEM
- Periodically checked for Mycoplasma contamination: yes
- Periodically checked for karyotype stability: yes
- Periodically "cleansed" against high spontaneous background: yes

Metabolic activation:

with and without

Metabolic activation system:

Rat liver S9

Test concentrations with justification for top dose:

Experiment I:
without S9 mix: 28.1; 56.3; 112.5; 225.0; 337.5; 450 µg/mL
with S9 mix: 56.3; 112.5; 225.0; 450.0; 675.0; 900.0 µg/mL
Experiment II:
without S9 mix: 28.1; 56.3; 112.5; 225.0; 450.0; 675.0 µg/mL
with S9 mix: 112.5; 225.0; 450.0; 900.0; 1350.0; 1800 µg/mL

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: water
- Justification for choice of solvent/vehicle: solubility properties

Controls

Negative solvent / vehicle controls:

yes

Remarks:

water

True negative controls:

no

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

Migrated to IUCLID6: 7,12-dimethylbenz(a)anthracene

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium


DURATION
- Exposure duration: 4 hours with and without metabolic activation in experiment 1, 24 hours without metaoblic activation in experiment 2
- Expression time (cells in growth medium): 72 hours
- Selection time (if incubation with a selection agent): 10 days

SELECTION AGENT (mutation assays): Thioguanine

NUMBER OF REPLICATIONS: 2

NUMBER OF CELLS EVALUATED: >1,5x10exp.6

DETERMINATION OF CYTOTOXICITY
- Method: cloning efficiency

Evaluation criteria:

A test item is classified as positive if it induces either a concentration-related increase of the mutant frequency or a reproducible and positive response at one of the test points.
A test item producing neither a concentration- related increase of the mutant frequency nor a reproducible positive response at any of the test points is considered non-mutagenic in this system.
A positive response is described as follows:
A test item is classified as mutagenic if it reproducibly induces a mutation frequency that is three times above the spontaneous mutation fre¬quency at least at one of the concentrations in the experiment.
The test item is classified as mutagenic if there is a reproducible concentration-related increase of the mutation frequency. Such evaluation may be considered also in the case that a threefold increase of the mutant frequency is not observed.

However, in a case by case evaluation this decision depends on the level of the corre-sponding negative control data. If there is by chance a low spontaneous mutation rate in the range normally found (0.5 – 31.8 mutants per 10exp.6 cells) a concentration-related in-crease of the mutations within this range has to be discussed. The variability of the mutation rates of negative and solvent controls within all experiments of this study was also taken into consideration.

Statistics:

Linear regression analysis (least squares) .

Results and discussion

Test results

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Summary Table

			relative	relative	mutant		relative	relative	mutant
	conc. µg	S9	cloning	cloning	colonies/	induction	cloning	cloning	colonies/	induction
	per mL	mix	efficiency I	efficiency II	10^6 cells	factor	efficiency I	efficiency II	10^6 cells	factor
			%	%			%	%
column	1	2	3	4	5	6	7	8	9	10
Experiment I / 4 h treatment			culture I				culture II
Solvent control with water		-	100.0	100.0	18.4	1.0	100.0	100.0	17.1	1.0
Positive control with	150.0	-	76.2	94.8	137.7	7.5	84.7	86.2	132.3	7.7
Test item	28.1	-	98.4	114.2	15.4	0.8	92.7	104.2	13.0	0.8
Test item	56.3	-	100.0	110.3	12.0	0.7	97.1	98.0	16.8	1.0
Test item	112.5	-	102.8	101.8	16.7	0.9	88.2	96.3	15.5	0.9
Test item	225.0	-	87.2	102.0	21.5	1.2	76.9	95.5	19.9	1.2
Test item	337.5	-	0.2	98.4	14.6	0.8	8.8	89.2	20.5	1.2
Test item	450.0	-	0.0	culture was not continued^#			0.0	culture was not continued^#
Solvent control with water		+	100.0	100.0	24.6	1.0	100.0	100.0	17.9	1.0
Positive control with DMBA	1.1	+	43.9	89.0	636.4	25.9	36.6	99.5	620.9	34.7
Test item	56.3	+	94.4	culture was not continued^##			97.3	culture was not continued^##
Test item	112.5	+	89.5	94.1	16.9	0.7	95.7	105.9	22.3	1.2
Test item	225.0	+	94.1	89.8	17.6	0.7	94.2	85.8	20.6	1.2
Test item	450.0	+	84.7	90.5	16.3	0.7	94.5	81.5	20.9	1.2
Test item	675.0	+	88.5	114.3	13.2	0.5	93.6	92.6	17.9	1.0
Test item	900.0	+	85.0	85.7	27.8	1.1	92.9	96.4	15.5	0.9
Experiment II / 24 h treatment			culture I				culture II
Solvent control with water		-	100.0	100.0	13.7	1.0	100.0	100.0	14.1	1.0
Positive control with	75.0	-	92.5	97.7	132.5	9.7	102.2	93.2	105.6	7.5
Test item	28.1	-	104.7	culture was not continued^##			101.8	culture was not continued^##
Test item	56.3	-	102.5	95.7	16.9	1.2	102.2	69.3	18.8	1.3
Test item	112.5	-	88.0	94.5	17.4	1.3	102.7	97.8	9.0	0.6
Test item	225.0	-	95.1	88.7	23.2	1.7	102.0	71.3	17.4	1.2
Test item	450.0	-	94.1	84.2	23.6	1.7	101.4	65.3	17.7	1.3
Test item	675.0	-	43.3	90.9	16.2	1.2	102.9	63.5	28.4	2.0
Experiment II / 4 h treatment			culture I				culture II
Solvent control with water		+	100.0	100.0	13.7	1.0	100.0	100.0	16.1	1.0
Positive control with DMBA	1.1	+	55.9	73.5	809.9	59.1	51.2	78.8	595.5	36.9
Test item	112.5	+	114.6	78.2	20.1	1.5	95.6	90.4	22.6	1.4
Test item	225.0	+	91.3	101.5	24.6	1.8	107.2	98.0	14.5	0.9
Test item	450.0	+	95.5	109.1	22.9	1.7	99.1	83.9	20.5	1.3
Test item	900.0	+	111.7	99.4	26.1	1.9	112.6	80.5	20.8	1.3
Test item	1350.0	+	10.6	100.7	11.4	0.8	7.4	102.9	8.8	0.5
Test item	1800.0	+	0.0	culture was not continued^#			0.0	culture was not continued^#

#     culture not continued due to exceedingly strong toxic effects

##    culture was not continued since a minimum of only four analysable concentrations is required

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

In conclusion it can be stated that under the experimental conditions reported the test item did not induce gene mutations at the HPRT locus in V79 cells.
Therefore, C-SAT 080094 is considered to be non-mutagenic in this HPRT assay.

Executive summary:

The study was performed to investigate the potential of C-SAT 080094 to induce gene mutations at the HPRT locus in V79 cells of the Chinese hamster.

The assay was performed in three independent experiments, using two parallel cultures each. The first main experiment was performed with and without liver microsomal activation and a treatment period of 4 hours. The experimental part without metabolic activation was terminated prematurely due to exceedingly severe cytotoxic effects even al low concentrations. This part of the first experiment was repeated in experiment IA using a lower concentration range. The data of the repeat experiment IA are included in the first experiment.

The second experiment was performed in the absence of metabolic activation with a treatment period of 24 hours and in the presence of metabolic activation with a treatment period of 4 hours.

The highest applied concentration in the pre-test on toxicity (7300 µg/mL) was based on the purity of the test item (36 % active ingredient). The dose range of the main experiments was limited by toxicity of the test item.

No substantial and reproducible dose dependent increase of the mutation frequency was observed in both main experiments.

Appropriate reference mutagens, used as positive controls, induced a distinct increase in mutant colonies and thus, showed the sensitivity of the test item and the activity of the metabolic activation system.