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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2005-09-15 to 2005-10-05
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:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1997
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Method

Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
E. coli WP2 uvr A
Metabolic activation:
with and without
Metabolic activation system:
Aroclor induced rat liver S9
Test concentrations with justification for top dose:
50, 150, 500, 1500, 5000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Ethanol

- Justification for choice of solvent/vehicle: Solubility properties and relative non-toxicity to bacteria
Controlsopen allclose all
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene
Remarks:
All salmonella strains + WP2 uvrA (with activation)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
2-nitrofluorene
Remarks:
TA 98 (without activation)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
TA 100, TA 1535 (without activation)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
Remarks:
TA 1537 (without activation)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
WP2 uvrA (without activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Expression time (cells in growth medium): 48 - 72 hours

NUMBER OF REPLICATIONS: 3 plates for each test concentration

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth; observation of background lawn density.

METABOLIC ACTIVATION: Aroclor induce rat liver S9; S9 mix included glucose-6-phophate and NADP as co-factors. 0.5ml of 10% S9 was added to 2 ml of top agar, 0.1 ml of tester strain and 0.05 ml of vehicle or test article giving a final concentration of approximately 2%.

Evaluation criteria:
A result is positive if the number of revertants is significantly increased compared with the solvent control to at least 2-fold of the solvent control for TA 98, TA 100 and WP2 uvrA and 3-fold of the solvent control for TA 1535 and TA 1537. There must be a dose related increase in the mean revertants per plate of at least one tester strain over a minimum of 2 increasing concentrations of test article.

Cytotoxicity is defined as a reduction in the number of colonies by >50% compared with the solvent control and/or at least a moderate reduction in
the background lawn (background code 3, 4 or 5).

Results and discussion

Test resultsopen allclose all
Key result
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid

Any other information on results incl. tables

Table 2a:  Toxicity and mutagenicity assay - plate incorporation (mean of 2 plates)

 

TA98

TA100

TA1535

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

0*

26

22

No

161

145

No

25

25

No

1.5

23

24

No

130

134

No

26

20

No

5

17

22

No

126

152

No

22

17

No

15

15

25

No

107

125

No

16

23

No

50

14

27

No

108

128

No

17

29

No

150

17

24

No

124

153

No

24

18

No

500

23

23

No

133

148

No

21

21

No

1500

16

20

No

115

129

No

27

20

No

5000

21

20

No

135

128

No

25

18

No

Positive Control

173

488

No

557

565

No

342

78

No

*solvent control with ethanol

Table 2b:  Toxicity and mutagenicity assay - plate incorporation (mean of 2 plates)

 

TA1537

WP2 uvrA

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

0*

11

9

No

28

13

No

1.5

8

8

No

17

25

No

5

8

8

No

22

19

No

15

7

8

No

27

17

No

50

6

5

No

20

19

No

150

7

8

No

22

24

No

500

7

7

No

16

24

No

1500

9

6

No

18

17

No

5000

8

10

No

22

17

No

Positive Control

871

62

No

141

203

No

*solvent control with ethanol

Table 3: Experiment 2 - preincubation Number of revertants per plate (mean of 3 plates)

 

TA98

TA100

TA1535

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

 MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

0*

18

24

No

84

84

No

16

21

No

50

15

19

No

80

72

No

17

20

No

150

15

26

No

51

97

No

15

19

No

500

17

21

No

78

81

No

19

24

No

1500

23

25

No

67

90

No

17

24

No

5000

15

24

No

80

103

No

20

21

No

Positive control

96

124

No

283

279

No

184

64

No

*solvent control with ethanol

Table 3: Experiment 2 - preincubation Number of revertants per plate (mean of 3 plates)

 

TA1537

WP2 uvrA

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

— MA

+ MA

Cytotoxic
(yes/no)

0*

9

9

No

25

20

No

50

7

7

No

18

26

No

150

5

9

No

23

21

No

500

8

5

No

20

16

No

1500

7

3

No

21

18

No

5000

8

7

No

20

17

No

Positive control

505

29

No

124

104

No

*solvent control with ethanol

Applicant's summary and conclusion

Conclusions:
Decamethyltetrasiloxane has been testing in a reliable study conducted according to OECD 471 1998 and under GLP up to limit concentrations. No increase in the number of revertants was observed at any concentration with and without metabolic activation in Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and E. coli WP2 uvrA in either the initial plate incorporation assay or the independent repeat experiment which used the pre-incubation method. It is considered that the test substance was negative for mutagenicity to bacteria under the conditions of the test.