4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998-08-03 to 1998-08-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Deviations:

no

GLP compliance:

yes

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane

EC Number:

260-350-7

EC Name:

4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane

Cas Number:

56706-10-6

Molecular formula:

C18H42O6S2Si2

IUPAC Name:

4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane

Constituent 2

Reference substance name:

S2

IUPAC Name:

S2

Method

Species / strain

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

Exp 1:7.5-120 µg/ml -S9, 10-500 µg/ml +S9; exp 2: 5-80 µg/ml -S9

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification: recommended by Sponsor

Controls

Controls 1

Untreated negative controls:

yes

Remarks:

test medium

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

without activation

Controls 2

Untreated negative controls:

yes

Remarks:

test medium

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

with activation

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION

- Exposure duration: 4 hours (with metabolic activation); 4, 18 and 28 hours (without metabolic activation)
- Expression time (cells in growth medium): 18 and 28 hours
- Fixation time (start of exposure up to fixation or harvest of cells): 18 and 28 hours

SPINDLE INHIBITOR (cytogenetic assays): Colcemid

STAIN (for cytogenetic assays): Giesma

NUMBER OF REPLICATIONS: Duplicate cultures; independent repeat experiment

NUMBER OF CELLS EVALUATED: 200 metaphases per experimental group per experiment were examined for structural chromosomal abnormalities. 1000 cells were scored to determine the mitotic index.

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index

OTHER EXAMINATIONS
- Determination of polyploidy: yes
- Determination of endoreplication: no data

METABOLIC ACTIVATION:
- Aroclor induced rat liver S9 prepared from Wistar rats with 43.7 mg/ml protein.
- S9 mix included 10% S9 and cofactor solution including MgCl2, KCl, Glucose-6-phosphate and NADP. Final concentration of S9 in cultures was approximately 1%.

Evaluation criteria:

A substance was considered negative when there was no statistically significant, biologically relevant and reproducible positive response at any test point, and no concentration related statistically significant and biologically relevant increase in structural chromosomal aberrations compared with the solvent control group.

Statistics:

Frequencies of metaphases with structural aberrations of test substance and positive control groups were compared with those of the solvent control group. A Chi squared test was applied.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

>50 % reduction in mitotic index at 40 μg/ml

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

>50 % reduction in mitotic index at 40 μg/ml (without metabolic activation); 100 μg/ml (with metabolic activation)

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: no significant effect
- Effects of osmolality: no significant effect
- Evaporation from medium: no data
- Water solubility: no data
- Precipitation: non-interfering precipitate noted at 100 μg/ml and above.
- Other confounding effects: none

RANGE-FINDING/SCREENING STUDIES: preliminary range finding test was carried out and cytotoxicity determined: 40 μg/ml (without metabolic activation) and 100 μg/ml (with metabolic activation

COMPARISON WITH HISTORICAL CONTROL DATA: control results were within the range of historical controls

Any other information on results incl. tables

Table 1 Chromosome aberrations Experiment 1

Without metabolic activation 4 h treatment, 18 h sampling
Treatment (μg/ml)	Number of cells analysed	Mitotic Index (mean of two cultures %)	Number of cells with Aberrations		% of cells with aberrations
			inc Gaps	excl Gaps	inc Gaps	excl Gaps
0^1	100+++	31.0	7	7	7.0	7.0
0^2	200	51.0	15	11	7.5	5.5
15	200	29.0	16	10	8.0	5.0
30	200	37.0	11	8	5.5	4.0
60	192++	6.5	11	9	5.7	4.7
Positive control	200	22.5	114**	110**	57.0	55.0
With metabolic activation 4 h treatment, 18 h sampling
Treatment (μg/ml)	Number of cells analysed	Mitotic Index (mean of two cultures %)	Number of cells with Aberrations		% of cells with aberrations
			inc Gaps	excl Gaps	inc Gaps	excl Gaps
0^1	200	78.5	16	12	8.0	6.0
0^2	200	106.5	13	9	6.5	4.5
31.6	200	70.5	12	8	6.0	4.0
100^P	200	106.0	22	16	11.0	8.0
60^P	200	28.5	21	18	10.5	9.0
Positive control	200	56.0	49**	47**	24.5	23.5
With metabolic activation 4 h treatment, 28 h sampling
Treatment (μg/ml)	Number of cells analysed	Mitotic Index (mean of two cultures %)	Number of cells with Aberrations		% of cells with aberrations
			inc Gaps	excl Gaps	inc Gaps	excl Gaps
0^1	100+++	77.0	5	7	5.0	4.0
0^2	200	90.5	18	15	9.0	7.5
31.6	200	75.0	8	7	4.0	3.5
100^P	200	99.0	11	8	5.5	4.0
60^P	200	52.5	22	19	11.0	9.5
Positive control	200	109.0	27	21	13.5	10.5

 

¹Negative control with culture medium

²Negative control with solvent (DMSO)

++ maximum number of evaluable metaphases on the slides examined

+++ determined from one culture only

* p<0.05

* p <0.01

^PPrecipitation Table 2 Chromosome aberrations Experiment 2

Without metabolic activation 18 h treatment, 18 h sampling
Treatment (μg/ml)	Number of cells analysed	Mitotic Index (mean of two cultures %)	Number of cells with Aberrations		% of cells with aberrations
			inc Gaps	excl Gaps	inc Gaps	excl Gaps
0^1	89+++	46.0	5	3	5.6	3.3
0^2	190++	32.5	11	7	5.8	3.7
10	142++	15.0	11	7	7.7	4.9
20	153++	16.0	10	7	6.5	4.6
40	200	8.0	11	7	5.5	3.5
Positive control	108++	12.5	12.5	26**	24.0	19.4
Without metabolic activation 28 h treatment, 28 h sampling
Treatment (μg/ml)	Number of cells analysed	Mitotic Index (mean of two cultures %)	Number of cells with Aberrations		% of cells with aberrations
			inc Gaps	excl Gaps	inc Gaps	excl Gaps
0^1	37+++	2.0	4	4	10.8	10.8
0^2	200	42.0	15	13	7.5	6.5
10	200	37.0	25	17	12.5	8.5
20	151++	43.5	6	4	4.0	2.6
40	88++	6.0	5	4	5.7	4.5
Positive control	158++	27.5	5.**	47**	31.6	29.7

¹Negative control with culture medium

²Negative control with solvent (DMSO)

++ maximum number of evaluable metaphases on the slides examined

+++ determined from one culture only

* p<0.05

* p <0.01

Applicant's summary and conclusion

Conclusions:

S2 has been tested according to OECD 473 and in compliance with GLP. No test substance-induced structural or numerical chromosomal aberrations were observed in Chinese hamster V79 fibroblasts when tested up to cytotoxic concentrations, with and without metabolic activation. The experiment was repeated and the results confirmed. Appropriate solvent and positive controls were included and gave expected results. It is considered that the substance is negative for cytogenicity under the conditions of the test.