Potassium methylsilanetriolate

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

Study period:

2003-10-16 to 2003-11-28

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP. The original study was reliability 1. Read-cross to the registered substance is considered scientifically justified and reliability 2.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2004

Report date:

2004

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:

Trimethoxy(methyl)silane

EC Number:

214-685-0

EC Name:

Trimethoxy(methyl)silane

Cas Number:

1185-55-3

IUPAC Name:

trimethoxy(methyl)silane

Method

Species / strain

Species / strain / cell type:

other: Chinese hamster ovary (CHO-K1) cells

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9, NADP as cofactor

Test concentrations with justification for top dose:

170.3, 340.6, 681.2 and 1362.4 µg/ml. The cells treated with 170.3 µg/ml were not evaluated for chromosome aberrations.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: based information provided by sponsor and compatibility with the 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:

ACTIVATION: 1 ml S9 mix containing 20 µl Aroclor induced rat liver S9, NADP as cofactor, added to 4 ml of medium
METHOD OF APPLICATION: in medium;
DURATION
- Preincubation period: none
- Exposure duration: 4 or 20 hours (without activation), 4 hours with activation
- Expression time (cells in growth medium): 0 or 16 hours
- Fixation time (start of exposure up to fixation or harvest of cells): 20 hours

SPINDLE INHIBITOR (cytogenetic assays): Colcemid added 2 h prior to harvest
STAIN (for cytogenetic assays): Giesma

NUMBER OF REPLICATIONS: duplicate cultures per concentration

NUMBER OF CELLS EVALUATED: mitotic index in 500 cells, aberrations in 200 cells (100 per duplicate flask)

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; other: cell count and percentage viability

OTHER EXAMINATIONS:
- Determination of polyploidy: yes
- Determination of endoreplication:yes

Evaluation criteria:

A test substance is considered positive if the percentage of cells with aberrations is increased in a dose-responsive manner with one or more concentrations being statistically significant. (p

Statistics:

Fisher's exact test; in the event of a positive result, Cochran Armitage test used to measure dose-responsiveness

Results and discussion

Test results

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

positive

Remarks:

with activation

Cytotoxicity / choice of top concentrations:

other: > 1362.4 μg/ml

Additional information on results:

RANGE-FINDING/SCREENING STUDIES: cell growth inhibition was between 7% and 17% in the highest dose tested.

COMPARISON WITH HISTORICAL CONTROL DATA: control values were within historical data.

ADDITIONAL INFORMATION ON CYTOTOXICITY:

Remarks on result:

other: other: Chinese hamster ovary (CHO-K1) cells

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

The percentage of cells with structural or numerical aberrations in the  non-activated 4 and 20 hour exposure groups was not significantly  increased above that of the solvent control at any dose level. The  percentage of cells with structural aberrations in the S9 activated 4  hour exposure group was significantly increased above that of the solvent  control at 1362.4 ug/mL. The Cochran-Armitage test was also positive for  a dose response. The percentage of cells with numerical aberrations in  the test article-treated group was not significantly increased above that  of the solvent control at any dose level. The results of the assay are  summarized in the following table:

WITHOUT S9:
Treatment time: 4 hr
Recovery time: 16 hr
Harvest time: 20 hr
Toxicity* at highest dose scored: 16%
Mitotic Index Reduction**: None
LED for Structural Aberrations (µg/mL): None
LED for Numerical Aberrations (µg/mL): None

WITHOUT S9:
Treatment time: 20 hr
Recovery time: 0 hr
Harvest time: 20 hr
Toxicity* at highest dose scored: 4%
Mitotic Index Reduction**: 9%
LED for Structural Aberrations (µg/mL): None
LED for Numerical Aberrations (µg/mL): None

WITH S9:
Treatment time: 4 hr
Recovery time: 16 hr
Harvest time: 20 hr
Toxicity* at highest dose scored: 22%
Mitotic Index Reduction**: 16%
LED for Structural Aberrations (µg/mL): 1362.4
LED for Numerical Aberrations (µg/mL): None

Where: 
* Cell growth inhibition
** Relative to solvent control at high dose evaluated for
chromosome aberrations
LED = Lowest Effective Dose

Table 1: 4 h treatment without activation (totals and percentages from 200 cells)

Treatment		Solvent Control	Positive control*	340.6 µg/ml	681.2 µg/ml	1362.4 µg/ml
Cytotoxicity		no	no	no	no	no
Chromatid aberrations	gaps	1	3	0	2	2
	breaks	1	14	1	0	0
	interchanges	0	13	1	1	.
Chromosome aberrations	breaks	0	0	0	0	0
	dicentric	0	0	1	2	3
	ring	0	0	0	0	0
Percent aberrant cells	Numerical	2.5	1.5	2	3	3
	Structural	0.5	29.0	1.5	1.5	2
Mitotic index		7.3	8.1	8.4	7.5	7.6

* 100 cells evaluated

 

Table 2: 4 h treatment with activation (totals and percentages from 200 cells)

Treatment		Solvent Control	Positive control*	340.6 µg/ml	681.2 µg/ml	1362.4 µg/ml
Cytotoxicity		no	yes	no	no	no
Chromatid aberrations	gaps	1	4	0	0	2
	breaks	1	30	0	0	7
	interchanges	0	19	0	0	13
Chromosome aberrations	breaks	0	0	0	0	0
	dicentric	0	3	2	2	2
	ring	0	0	0	0	0
Percent aberrant cells	Numerical	2	1.5	1.5	3.5	4.0
	Structural	0.5	22.5	1.0	3.0	9.5
Mitotic index		9.3	8.6	8.4	8.2	7.8

* 100 cells evaluated

 

Table 3: 20 h treatment without activation (totals and percentages from 200 cells)

Treatment		Solvent Control	Positive control*	340.6 µg/ml	681.2 µg/ml	1362.4 µg/ml
Cytotoxicity		no	no	no	no	no
Chromatid aberrations	gaps	1	6	0	1	1
	breaks	1	28	0	0	0
	interchanges	0	18	0	1	0
Chromosome aberrations	breaks	0	0	0	0	0
	dicentric	0	2	3	4	4
	ring	0	1	0	0	0
Percent aberrant cells	Numerical	2	1.5	2	1.5	1.5
	Structural	0.5	20	1.5	2.5	2.0
Mitotic index		7.9	7.4	6.8	7.0	6.3

* 100 cells evaluated

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
positive with metabolic activation
negative without metabolic activation

Trimethoxy(methyl)silane has been tested in a valid study conducted according to OECD 473 and in compliance with GLP. The test substance induced a statistically significant dose related increase in the number of structural aberrations in Chinese hamster ovary (CHO-K1) cells in the presence of activation. No test-substance related genotoxicity was observed in the absence of metabolic activation. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is positive for the induction of chromosome aberrations in the presence of activation under the conditions of the study.