Trichloro(hexadecyl)silane

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:

02 Sep 2004 to 03 Dec 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Version / remarks:

(adopted 1997)

Deviations:

no

GLP compliance:

yes

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

Hexadecyltrimethoxysilane

EC Number:

240-464-3

EC Name:

Hexadecyltrimethoxysilane

Cas Number:

16415-12-6

Molecular formula:

C19H42O3Si

IUPAC Name:

Hexadecyl(trimethoxy)silane

Test material form:

other: liquid

Details on test material:

- Name of test material (as cited in study report): Dynasylan 9116
- Physical state: colourless liquid
- Expiration date of the lot/batch: 06 Aug 2005
- Storage condition of test material: ambient temperature

Method

Target gene:

Not applicable

Species / strain

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Metabolic activation system:

phenobarbital and beta-naphthoflavone induced rat liver S9

Test concentrations with justification for top dose:

Experiment I:
- 10.2, 20.3, 40.6, 81.3, 163, 325, 650 and 1300 µg/ml (with and without metabolic activation)
Experiment II:
- 10.2, 20.3, 40.6, 81.3, 163, 325, 650 and 1300 µg/ml (with and without metabolic activation)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: ethanol
- Justification for choice of solvent/vehicle: Solubility properties and relative non-toxicity to cells

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: -S9-mix: mitomycin C: 0.3 µg/ml (3 h treatment), 0.1 µg/ml (20 h treatment); +S9-mix: cyclophosphamide: 15 µg/ml (3 h treatment)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Preincubation period:
- Exposure duration: 3 h and 20 h
- Fixation time (start of exposure up to fixation or harvest of cells): 20 h

SPINDLE INHIBITOR (cytogenetic assays): colcemid (0.2 µg/ml; added 3 hours before harvest)

STAIN (for cytogenetic assays): Giemsa (3%)

NUMBER OF REPLICATIONS: 2 independent experiment

NUMBER OF CELLS EVALUATED: 100 cells from each culture were evaluated for chromosome abberations.

DETERMINATION OF CYTOTOXICITY
- Method: relative cell count

Evaluation criteria:

The test item is considered to have clastogenic properties if there is a statistically significant increase in the incidence of cells bearing aberrations at any dose level over the concurrent control. The increase must exceed historical control values. The increases must be reproduced in both cultures.

Statistics:

Where necessary, the frequency of cells with aberrations excluding gaps, and the frequency of polyploid cells was compared with the concurrent vehicle control using Fischer's Exact test.

Results and discussion

Test results

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Experiment 1: cytotoxicity at 650 µg/mL (+S9) and 1300 µg/mL (±S9); Experiment 2: cytotoxicity at 10.2, 20.3 and 40.6 µg/mL (-S9). Precipitation was observed in the culture medium at 650 and 1300 µg/mL at the start and end of treatment.

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

Full study data tables are attached and summarized data is provided in the field "Any other information on results incl. tables".

CYTOTOXICITY:
- In Experiment 1 in the absence of S9, slight toxicity was observed at 1300 µg/mL, with the cell count reduced to 74% of the control value. No relevant toxicity was observed for the remaining dose levels.
- In Experiment 1 in the presence of S9, slight toxicity was seen at 650 and 1300 µg/mL, with the cell counts reduced to 75% and 70% of the controls respectively.
- In Experiment 2 in the absence of S9, severe toxicity was seen at 81.3 to 1300 µg/mL, with few or no cells observed. Moderate toxicity was observed at 20.3 and 40.6 µg/mL, with cells counts reduced to 51 and 34% of the controls respectively. Mild toxicity was observed at the lowest dose level of 10.2 µg/mL, with the cell count reduced to 65% of the control.

GENOTOXICITY
- For both Experiment 1 and Experiment 2 there were no statistically significant increases in the incidence of cells bearing aberrations (including and excluding gaps).
- In Experiment 1, no relevant increase in the incidence of cells bearing aberrations (including or excluding gaps) over the control value was observed.
- In Experiment 2, a slight increase in the incidence of cells bearing aberrations (including or excluding gaps) over the control value was observed at the intermediate dose level (20.3 µg/mL). This however was not considered as biologically meaningful since the incidence was within the range of the historical controls and corresponded to the concurrent value for the untreated controls.

POSITIVE CONTROLS
- Statistically significant increases in the frequency of cells bearing aberrations (including and excluding gaps) were seen for the positive control substances, indicating the correct functioning of the assay system.

COMPARISON WITH HISTORICAL CONTROL DATA: Results were within range of historical control data (see attached data tables).

Any other information on results incl. tables

Table 2: Results of chromosome analysis Experiment 1, 3h treatment without activation (total count from 2 cultures)

		Untreated ***	Solvent* Control***	Positive Control**	Low dose***	Mid dose***	High dose***
		Mean
Chromatid aberrations	gaps	0	0	3	0	0	1
	deletions	0	0	25	0	0	0
	interchanges	0	0	49	0	0	0
Chromosome aberrations	gaps	NR	NR	NR	NR	NR	NR
	deletions	0	0	3	0	0	0
	interchanges	0	0	0	0	0	0
Mitotic index		NR	NR	NR	NR	NR	NR
Polyploidy		0	0	0	0	0	0
Endo reduplication		0	0	0	0	0	0

 *Solvent control with ethanol

** Per 150 cells

*** Per 200 cells

NR not reported

 

Table 3: Results of chromosome analysis Experiment 1, 3h treatment with activation (total count from 2 cultures)

		Untreated ***	Solvent* Control***	Positive Control**	Low dose***	Mid dose***	High dose***
		Mean
Chromatid aberrations	gaps	0	0	3	0	0	1
	deletions	0	0	25	1	0	22
	interchanges	0	0	49	0	0	40
Chromosome aberrations	gaps	NR	NR	NR	NR	NR	NR
	deletions	0	0	3	0	0	5
	interchanges	0	0	0	0	0	0
Mitotic index		NR	NR	NR	NR	NR	NR
Polyploidy		0	0	0	0	0	0
Endo reduplication		2	0	0	0	0	0

 *Solvent control with ethanol

** Per 150 cells

*** Per 200 cells

NR not reported

 

Table 4: Results of chromosome analysis Experiment 2, 20h treatment without activation (total count from 2 cultures)

		Untreated ***	Solvent* Control***	Positive Control**	Low dose***	Mid dose***	High dose***
		Mean
Chromatid aberrations	gaps	0	0	0	0	0	1
	deletions	1	1	7	1	1	0
	interchanges	4	0	52	0	1	0
Chromosome aberrations	gaps	NR	NR	NR	NR	NR	NR
	deletions	0	0	9	2	3	0
	interchanges	0	0	0	0	0	0
Mitotic index		NR	NR	NR	NR	NR	NR
Polyploidy		0	0	0	0	0	0
Endo reduplication		0	0	0	0	0	0

 *Solvent control with ethanol

** Per 150 cells

*** Per 200 cells

NR not reported

 

Applicant's summary and conclusion

Conclusions:

Interpretation of results:
negative

The substance was tested to OECD 473 (1997) under GLP. The test material did not induce any statistically significant, dose-related increases in the frequency of cells with chromosomal aberrations either in the presence or absence of metabolic activation or after various exposure times. The test material was therefore considered to be non-clastogenic to CHO cells in vitro under the conditions of the test.