Disodium disilicate

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-guideline study For justification for read across see endpoint summary.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

GLP compliance:

yes

Remarks:

RCC-Cytotest Cell Research GmbH

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid, sodium salt

EC Number:

215-687-4

EC Name:

Silicic acid, sodium salt

Cas Number:

1344-09-8

IUPAC Name:

sodium hydroxy(oxo)silanolate

Details on test material:

CAS 1344-09-8
Sodium silicate solution (weight ratio 3.3)
Tradename: Natronwasserglas 37/40 PE
36% active ingredient, 64% water

Method

Species / strain

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Details on mammalian cell type (if applicable):

CELL CULTURE DETAILS:
- Type and identity of media: Minimal Essential Medium supplemented with  10% fetal calf serum.
- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically checked for karyotype stability: yes

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital / ß-Naphthoflavone induced  rat liver S9-mix

Test concentrations with justification for top dose:

19.5, 39.1, 78.1 & 156.3 µg active ingredient/ml

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

medium

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 300-400 µg/ml  Ethylmethane sulfonate (-S9), 1.4-2.0 µg/ml Cyclophosphamide (+S9)

Details on test system and experimental conditions:

- Spindle inhibitor: 0.2 µg/ml Colcemid
- Stain: Giemsa
- No. of metaphases analyzed: 100
- Dosing: Cytotoxic concentrations were determined in a range-finder study with and without metabolic activation. 312.5 µg/ml was chosen as  top concentration in the actual experiments.
- Number of replicates: 2

Evaluation criteria:

Breaks, fragments, deletions, exchanges,  and chromosome disintegrations were recorded as structural chromosome  aberrations. Gaps were recorded as well, but not included in the  calculation of aberration rates. Only metaphases with characteristic  chromosome numbers (22+-1) were included in the analysis. The mitotic  index (% cells in mitosis) and the percentage of polyploid cells in 500  metaphase plates/culture were determined.

Results and discussion

Test results

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: 156.3 - 312.5 µg active ingredient/mL

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

PRECIPITATION CONCENTRATION:

156.3 µg active ingredient/ml (except experiment II after 18h preparation interval without S9 mix where precipitation occurred at 78.1 µg/ml and above)

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

Sodium silicate showed no chromosome aberratins in V79 cells in vitro.

Executive summary:

In a mammalian cell cytogenetics assay (Chromosome aberration assay) V79 cell cultures were exposed to sodium silicate (36% active ingredient, 64% water) at concentrations of 19.5, 39.1, 78.1 & 156.3 µg active ingredient/ml with and without metabolic activation (Phenobarbital / ß-Naphthoflavone induced rat liver S9-mix).

Sodium silicate was tested up to cytotoxic or precipitating concentrations. Positive controls induced the appropriate response. There was no evidence of chromosome aberration induced over background.

This study is classified as acceptable. This study satisfies the requirement for Test Guideline (In vitro mammalian cytogenetics, OECD 473) for in vitro cytogenetic mutagenicity data.