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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro cytogenicity / chromosome aberration study in mammalian cells
Type of information:
experimental study
Adequacy of study:
supporting 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

Constituent 1
Chemical structure
Reference substance name:
Trimethoxysilane
EC Number:
219-637-2
EC Name:
Trimethoxysilane
Cas Number:
2487-90-3
Molecular formula:
C3H10O3Si
IUPAC Name:
trimethoxysilane

Method

Species / strain
Species / strain / cell type:
other: CHO cells
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.
Controlsopen allclose all
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
mitomycin C
Remarks:
(without activation)
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 resultsopen allclose all
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
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:
In a reliable study, conducted in accordance with OECD 473, 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 S9-activated test system at the highest dose tested.