Dichloro(diphenyl)silane

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 Apr - 14 Nov 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:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

July 1997

Deviations:

yes

Remarks:

Did not include strain to detect cross-linking mutagens.

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Dichloro(diphenyl)silane

EC Number:

201-251-0

EC Name:

Dichloro(diphenyl)silane

Cas Number:

80-10-4

Molecular formula:

C12H10Cl2Si

IUPAC Name:

dichlorodiphenylsilane

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/solvent used: Ethylene glycol dimethylether (EGDE, dryed with a molcular sieve, 0.4 nm)

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

other: nitrofurantoin (NF), 4-nitro-1,2-phenyl diamine (4-NPDA), 2-aminoanthracene (2-AA)

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: in 2 independent experiments
- Number of cultures per concentration: quadruplicates
- Number of independent experiments: 2 for strain TA 98, TA 100 and TA 1537; 5 for strain TA 1535

DETERMINATION OF CYTOTOXICITY
- Method: Gross appraisal of background growth on the plate, marked or dose-dependent reduction in the mutant count per plate compared to the negative controls 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 TA 1535, 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.

Acceptance criteria
a) The negative controls had to be within the expected range, as defined by published data and/or the laboratories own historical control data.
b) The positive controls had to show sufficient effects, as defined by the laboratories' experience.
c) Titer determinations had to demonstrate sufficient bacterial density in the suspension.
Onlyl trials which complied with all three of the above criteria were accepted for assessment. Even if the criteria for points b) and c) were not met, a trial was accepted, if it showed mutagenic activity of the test substance.

Results and discussion

Test results

Test results 1

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Test results 2

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Test results 3

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Test results 4

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

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 the test substance 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 the test substance 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
200	31	104	9	23
1000	30	105	8	29
5000	B	B	B	B
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	8B	27
500	38B	144	6B	22B
1000	32B	117B	6B	17B
Na-azide	897	-		-
NF	-	531	-	-
4-NPDA	-	-	83	60

NF: nitrofurantonin;

4-NPDA: 4-nitro-1,2-phenyl diamine

B: Background lawn reduced

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*
200	17*	119*	12	39*
1000	16*	119B*	12*	34*
5000	B*	B*	B*	B*
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	19B*	119B*	7B*	36B*
2-AA	213	1268	126	1107

2-AA: 2-aminoanthracene

B: Background lawn reduced

*: Bacteriotoxic effect (based on titer determination; studied on two plates for each concentration with S9 mix)

Table 3. Summary of mean values for TA 1535 without S9 mix.

Pre-incubation method µg/plate	Strain
	TA 1535	TA 1535	TA 1535
0	27	29
31.25	30	22
62.5	32	29
125	31	31
250	51	35
500	33B*	52B*
1000	40B*	55B*
Na-azide	883	848
0	12	15	12
100	15*	19	12
200	19*	18*	13*
400	20*	15*	11*
600	17B*	17B*	10B*
800	15B*	8B*	7B*
1000	11B*	9B*	10B*
1200	8B*	10B*	7B*
Na-azide	855	639	648
0	11	11	18
100	11	14	16
200	11	12	17
400	13	12	15
600	10	13	11
800	9	12	10
1000	10	11	9
1200	10*	12*	10*
Na-azide	714	700	678

B: Background lawn reduced

*: Bacteriotoxic effect (based on titer determination; studied on two plates for each concentration without S9 mix)

Plate incorporation method:

There was no indication of a bacterial toxic effect of the test substance at 8 µg per plate. The total bacterial counts consistently produced results comparable to the negative controls, or differed only insignificantly (Table 1 and 2). 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 the test substance 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 (Table 1 and 2). 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 without metabolic activation (Table 1). This increase did, however, not correlate with dose and could not be confirmed (Table 3). 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 dichloro(diphenyl)silane 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.