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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:
30-04-1994 To 14-11-1994
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
the range of strains does not comply with the current guideline

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1994
Report Date:
1994

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
yes
Remarks:
Did not include strain to detect cross-linking mutagens.
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Method

Target gene:
His operon
Species / strain
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Additional strain / cell type characteristics:
other: rfa, uvrB and pKM101 (TA98 & TA100)
Metabolic activation:
with and without
Metabolic activation system:
cofactor supplemented post-mitochondrial fraction (S9 mix), prepared from the livers of rats treated with Aroclor 1254.
Test concentrations with justification for top dose:
8-5000 µg/plate - Plate incorporation method.
31.25-1200 µg/plate - Pre-incubation method.
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Ethylene glycol dimethylether (EGDE, dryed with a molcular sieve, 0.4 nm)
Controlsopen allclose all
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: nitrofurantoin
Remarks:
-S9: TA 100: 0.2 µg per plate.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
-S9: TA 1535: 10 µg per plate.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: phenylene diamine
Remarks:
-S9: TA1537 and TA98 : 10 and 0.5 µg per plate, respectively.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene
Remarks:
+ S9: All strains: 3 µg per plate.
Details on test system and experimental conditions:
METHOD OF APPLICATION:in agar (plate incorporation) and preincubation;

DURATION
- Preincubation period: 30 minutes
- Exposure duration: 48 hours


NUMBER OF REPLICATIONS: 4

DETERMINATION OF CYTOTOXICITY
- Method: Gross appraisal of background growth on the plate, marked or dose-dependent reduction in the mutant count per plate and the titer was determined.


Metabolic activation system: It was made from the livers of at least six adult male Sprague-Dawley rats, of approximately 200 to 300 g in weight. For enzyme induction, the animals received a single intraperitoneal injection of Aroclor 1254, dissolved in corn oil, at a dose of 500 mg/kg bw, five days prior to sacrifice. The S9 mix also contained seventy mL of cofactor solution containing the following:

-MgCl2 x 6H2O (162.6 mg)
-KCl (246.0 mg)
-Glucose-6-phophate, disodium salt (179.1 mg)
NADP, disodium salt (315.0 mg)
-Phosphate buffer (100.0 mg)

Evaluation criteria:
A reproducible and dose-related increase in mutant counts of at least one strain is considered to be a positive result. For TA1535, TA 100 and TA 98 this increase should be about twice that of negative controls, whereas TA 1537, at least a threefold increase should be reached. However, these guidelines may be overruled by good scientific judgement.

Results and discussion

Test results
Species / strain:
S. typhimurium, other: TA 1535, TA 1537, TA 98, TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
>62.5 µg/plate
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
ADDITIONAL INFORMATION ON CYTOTOXICITY: The salmonella/ microsome plate incorporation test, employing doses of up to 5000 µg per plate, showed diphenyldichlorosilane to produce bacterial toxic effects at 40 µg per plate and above. Therefore, 5000 µg per plate could not be used for assessment. The salmonella/ microsome test, using preincubation for 30 minutes at 37 °C and employing doses of up to 1200 µg per tube, showed diphenyldichlorosilane to produce bacterial toxic effects at 100 µg per tube and above.

Any other information on results incl. tables

Table 1. Summary of mean values without S9 mix.

Groups

Strain

TA 1535

TA 100

TA 1537

TA 98

Plate incorporation method (µg/plate)

 

 

 

 

0

25

120

12

23

8

26

116

9

24

40

27

117

11

24

20

31

104

9

23

1000

30

105

8

29

5000

-

-

-

-

Na-azide

926

 

 

 

NF

 

378

 

 

4-NPDA

 

 

101

118

Pre-incubation method- µg/plate

 

 

 

 

0

22

143

13

31

31.25

29

146

13

31

62.5

36

157

14

31

125

30

166

15

28

250

43

134

8

27

500

38

144

6

22

1000

32

117

6

17

Na-azide

897

 

 

 

NF

 

531

 

 

4-NPDA

 

 

83

60

Table 2. Summary of mean values with S9 mix.

Groups

Strain

TA 1535

TA 100

TA 1537

TA 98

Plate incorporation method (µg/plate)

 

 

 

 

0

21

150

16

42

8

19

146

12

44

40

18

142

14

42

20

17

119

12

39

1000

16

119

12

34

5000

-

-

-

-

2-AA

211

1476

117

891

Pre-incubation method (µg/plate)

 

 

 

 

0

17

141

10

40

31.25

17

151

12

38

62.5

17

148

13

46

125

22

166

11

45

250

19

154

11

48

500

21

168

11

41

1000

19

119

7

36

2-AA

213

1268

126

1107

Plate incorporation method:

There was no indication of a bacterial toxic effect of diphenylchlorosilane at 8 µg per plate. The total bacterial counts consistently produced results comparable to the negative controls, or differed only insignificantly. No inhibition of growth was noted as well. None of the four strains concerned showed a dose- related and biologically relevant increase in mutant counts over those of the negative controls. This applied both to the tests with and without S9-mix.

 Pre-incubation method:

There was no indication of a bacterial toxic effect of diphenylchlorosilane at doses of up to and including 62.5 µg per tube. The total bacteria counts consistently produced results comparable to the negative controls, or differed only insignificantly. No inhibition of growth was noted as well. One of the four strains concerned revealed an increase in mutant counts to double those of negative controls. Strains TA 1535 were affected. This increase did, however, not correlate with dose and could not be confirmed. Therefore, it was considered to be of no relevance.

The positive controls sodium azide, nitrofurantonin, 4-nitro-1,2-phenyl diamine and 2-aminoanthracene increased mutant counts well over those of the negative controls, and thus demonstrated the system’s sensitivity and the activity of the S9 mix

Applicant's summary and conclusion

Conclusions:
Interpretation of results: negative with and without metabolic activation

In a bacterial mutagenicity assay according to OECD 471 and GLP, no indications of mutagenic effects of diphenyldichlorosilane was found at assessable doses of up to 1200 µg per plate in any of the Salmonella typhimurium strains used in the plate incorporation assay and in the preincubation assay.