Trichlorosilane

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:

2006-08-16 to 2006-09-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

GLP compliance:

yes

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

Trimethoxysilane

EC Number:

219-637-2

EC Name:

Trimethoxysilane

Cas Number:

2487-90-3

Molecular formula:

C3H10O3Si

IUPAC Name:

Trimethoxysilane

Test material form:

liquid

Method

Species / strain

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

152.5 to 1220 µg/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO

- Justification for choice of solvent/vehicle: solubility of the test article and compatibility with target cells.

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

mitomycin C

Remarks:

(without activation)

Controls 2

Untreated negative controls:

no

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

- Preincubation period: 16 - 24 hours

- Exposure duration: 4 - 20 hours (-MA), 4 hours (+MA)

NUMBER OF REPLICATIONS: 2 flasks per concentration

DETERMINATION OF CYTOTOXICITY

- Method: Cell growth inhibition relative to the solvent control

Evaluation criteria:

Toxicity based on cell growth inhibition relative to solvent control.

The number and types of aberrations found, % aberrant cells in the total population of cells examined, and mean aberrations per cell were calculated and reported for each treatment group.

The test article was considered to induce a positive response when the percentage of cells with aberrations is increased in a dose-responsive manner with one or more concentrations being statistically significant (p≤0.05).

Statistics:

Fisher's exact test was used to compare pairwise the percent aberrant cells of each treatment group with that of the solvent control. In the event of a positive Fisher's Exact test at any test article dose level, the Cochran-Armitage test was used to measure dose-responsiveness.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with

Genotoxicity:

other: positive structural, negative numerical

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

1220 µg/ml (4 hour group)

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

1220 µg/ml (4 hour group)

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Any other information on results incl. tables

Table 1: Preliminary toxicity test using Trimethoxysilane in CHO cells with and without S9 metabolic activation (4 hour treatment / 16 hour recovery) 

	- MA			+ MA			- MA
	4 hour treatment / 16 hour recovery						20 hour continuous treatment)
Treatment μg/ml	Cell Viability (%)	Cell Growth Index (%) *	Cell Growth Inhibition (%) **	Cell Viability (%)	Cell Growth Index (%) *	Cell Growth Inhibition (%) **	Cell Viability (%)	Cell Growth Index (%) *	Cell Growth Inhibition (%) **
DMSO	98	100	-	98	100	-	100	100	-
0.122	99	95	5	100	89	11	99	86	14
0.366	99	79	21	100	96	4	99	92	8
1.22	100	82	18	97	97	3	100	85	15
3.66	97	76	24	99	80	20	97	87	13
12.2	99	78	22	97	81	19	95	86	14
36.6	98	67	33	98	86	14	96	99	1
122	98	63	37	100	98	2	97	94	6
366	99	68	32	99	78	22	98	87	13
1220	93	41	59	95	42	58	91	67	33

* Cell Growth Index = (cells per flask treated group/cells per flask control group), expressed as a percentage

** Cell Growth Inhibition = 100 % - % cell growth index; not calculated for negative controls 

Table 2: Cytogenetic analysis of CHO cells in the absence of metabolic activation (4 hour treatment, 16 hour recovery period)

		Control*		152.5 μg/ml		305 μg/ml		610 μg/ml		Positive control
Flask		A	B	A	B	A	B	A	B	A	B
Cytotoxicity		no	no	no	no	no	no	yes	yes	no	no
Chromatid aberrations***	Breaks	0	0	0	0	0	0	1	0	10	7
	Interchanges	0	0	0	0	0	0	0	0	0	1
Chromosome aberrations***	Gaps**	0	0	1	0	0	0	0	0	1	0
	Breaks	0	0	0	0	0	0	0	0	0	0
	Dicentric	0	0	0	0	0	0	0	0	0	0
	Rings	0	0	0	0	0	0	0	0	0	0
% aberrant cells	Numerical	2	3	5	5	4	5	3	3	1	2
	Structural	0	0	0	0	0	0	1	0	28	24
Mitotic index		11.0	11.4	10.8	10.4	10.0	10.4	9.6	8.8	7.4	6.8

* Solvent control with DMSO

** Total gaps

*** Total number of aberrations

Mitotic Index = number of mitotic figures x 100/500 cells counted

% Aberrant Cells: numerical cells include polyploid and endoreduplicated cells; structural cells exclude cells with only gaps

 

Table 3: Cytogenetic analysis of CHO cells in the presence of metabolic activation (4 hour treatment, 16 hour recovery period)

 

		Control*		152.5 μg/ml		305 μg/ml		1220 μg/ml		Positive control
Flask		A	B	A	B	A	B	A	B	A	B
Cytotoxicity		no	no	no	no	no	no	yes	yes	yes	yes
Chromatid aberrations***	Breaks	0	0	0	1	0	2	1	8	2	7
	Interchanges	0	0	1	1	3	1	7	4	8	6
Chromosome aberrations***	Gaps**	1	0	1	0	2	0	2	3	0	1
	Breaks	0	0	0	0	0	0	0	0	0	0
	Dicentric	0	1	0	0	0	0	1	1	0	0
	Rings	0	0	0	0	0	0	0	0	2	1
% aberrant cells	Numerical	5	4	5	5	5	4	3	4	5	4
	Structural	0	1	1	2	3	3	8	9	16	18
Mitotic index		11.6	11.6	11.2	11.4	10.6	11.2	5.4	6.4	4.0	3.8

* Solvent control with DMSO

** Total gaps

*** Total number of aberrations

Mitotic Index = number of mitotic figures x 100/500 cells counted

% Aberrant Cells: numerical cells include polyploid and endoreduplicated cells; structural cells exclude cells with only gaps

 

Table 4: Cytogenetic analysis of CHO cells in the absence of metabolic activation (20 hour continuous treatment

		Control*		152.5 μg/ml		305 μg/ml		610 μg/ml		Positive control
Flask		A	B	A	B	A	B	A	B	A	B
Cytotoxicity		no	no	no	no	no	no	yes	yes	no	no
Chromatid aberrations***	Breaks	0	0	0	0	0	1	0	0	4	3
	Interchanges	0	0	0	0	0	0	0	0	2	3
Chromosome aberrations***	Gaps**	0	0	0	0	0	0	0	1	1	0
	Breaks	0	0	0	0	0	0	0	0	0	0
	Dicentric	0	0	0	0	0	0	0	0	0	0
	Rings	0	0	0	0	0	0	0	0	0	0
% aberrant cells	Numerical	3	4	4	4	4	3	4	4	4	3
	Structural	0	0	0	0	0	1	0	0	24	20
Mitotic index		10.4	10.0	10.2	10.4	9.4	10.0	5.2	4.8	6.6	6.0

* Solvent control with DMSO

** Total gaps

*** Total number of aberrations

Mitotic Index = number of mitotic figures x 100/500 cells counted

% Aberrant Cells: numerical cells include polyploid and endoreduplicated cells; structural cells exclude cells with only gaps

 

 

Applicant's summary and conclusion

Conclusions:

Trimethoxysilane (CAS 2487-90-3) has been tested in a reliable in vitro mammalian cytogenicity study, conducted according to OECD Test Guideline 473 and in compliance with GLP. Trimethoxysilane was concluded to be positive for the induction of structural and negative for the induction of numerical chromosome aberrations in CHO cells in the presence of metabolic activation system at the highest dose tested. No chromosomal aberrations were noted when tested in the absence of metabolic activation. Appropriate solvent and positive controls were included and gave the expected results.  It is concluded that trimethoxysilane is positive for the induction of chromosome aberrations in vitro under the conditions of the test.