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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:
1995-02-06 - 1995-02-16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1995
Report date:
1995

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
OECD not actually specified but mentioned in 'Statement of Compliance'.
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

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 pKM 101
Species / strain / cell type:
E. coli, other: WP2 pKM101
Metabolic activation:
with and without
Metabolic activation system:
Aroclor induced rat liver S9
Test concentrations with justification for top dose:
100, 333, 1000, 3333 and 5000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Acetone
- Justification for choice of solvent/vehicle: Sponsor's request and compatibility with the target cells.
NOTE: the solvent is described as acetone in the method section but in most of the tables of results it is reported to be DMSO. It is thought by the reviewer that this is a typographical error: if DMSO was used rather than acetone the study would still be valid.
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 1.0 µg/plate
Remarks:
TA98, TA100, TA1535, TA1537 with metabolic activation
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene 10 µg/plate
Remarks:
WP2 uvrA (pKM101) with metabolic activation
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: sterigmatocystin 100 µg/plate
Remarks:
WP2 (pKM101) with metabolic activation
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
2-nitrofluorene
Remarks:
TA98 without metabolic activation 1.0 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
TA100, TA1535 without metabolic activation 1.0 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
Remarks:
TA1537 without metabolic activation 75 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
WP2 uvrA (pKM101), WP2 (pKM101) without metabolic activation 1,000 µg/plate
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

ACTIVATION: S9 mix contained glucose-6-phosphate and NADP as co-factors. Concentration of S9 in the mix was 10%. 0.5mlk of S9 mix were added to a total volume of 2.65ml, giving a final concentration of approximately 2% S9.

DURATION
- Preincubation period: 60 minutes +/- 2 minutes at 37ºC
- Exposure duration: 48 - 72 hours at 37ºC


SELECTION AGENT (mutation assays): histidine deficient agar

NUMBER OF REPLICATIONS: triplicate plates

DETERMINATION OF CYTOTOXICITY
- Method: other: condition of background lawn



Evaluation criteria:
For the test to be evaluated positive, it must cause a dose-related increase in the mean revertants per plate of at least one tester strain with a minimum of two increasing concentrations of test article. TA1535 and TA1537 were judged positive if the increase in mean revertants is equal to or greater than three times the mean vehicle control value. TA98, TA100, WP2 uvrA (pKM101) and WP2 (pKM101) were judged positive in the increase in mean revertants is equal to or greater than two times the mean vehicle control value.
Statistics:
None stated in report

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 pKM 101
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, other: WP2 (pKM101)
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
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS

- Precipitation: Precipitation was observed at 333 µg/plate and above

ADDITIONAL INFORMATION ON CYTOTOXICITY: Cytotoxicity was not evident at any concentration
Remarks on result:
other: No mutagenic potential

Any other information on results incl. tables

Summary of results – Experiment B1 revertants per plate (mean of 3 plates)

Dose µg/plate

+/-

metabolic activation

Average revertants per plate

TA98

TA100

TA1535

TA1537

WP2 uvrA (pKM101)

WP2 (pKM101)

Solvent control

-

21

143

11

7

210

44

100

-

19

158

11

6

212

52

333

-

24

141

11

7

199

50

1000

-

20

136

15

6

232

48

3333

-

20

142

14

4

163

53

5000

-

22

153

14

6

169

46

Positive control

-

804

675

467

156

1963

205

Solvent control

+

28

157

15

9

276

58

100

+

27

159

15

9

294

61

333

+

29

188

10

8

242

50

1000

+

30

182

12

8

254

52

3333

+

30

157

14

7

287

55

5000

+

28

180

12

7

270

58

Positive control

+

1363

1241

94

179

1395

2018

NOTE: the solvent is described as acetone in the method section but in most of the tables of results it is reported to be DMSO. It is thought by the reviewer that this is a typographical error, however if DMSO was used rather than acetone the study would still be valid.

Applicant's summary and conclusion

Conclusions:
Silsesquioxanes, phenyl has been tested for mutagenicity to bacteria, in a study which was conducted according to a protocol that was similar to OECD 471, and in compliance with GLP. No evidence of a test substance related increase in the number of revertants was observed with or without activation in the experiment. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.