Trimethylsilane

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:

2001-02-01 to 2001-05-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

only duplicate plates were used, and 2-aminoacridine was the only positive control with metabolic activation

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Trimethylsilane

EC Number:

213-603-0

EC Name:

Trimethylsilane

Cas Number:

993-07-7

Molecular formula:

C3H10Si

IUPAC Name:

trimethylsilane

Test material form:

not specified

Method

Target gene:

histidine operon (S. typhimurium); tryptophan operon (E. coli)

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Additional strain / cell type characteristics:

other: E. coli is strain WP2 uvrA / pKM101

Metabolic activation:

with and without

Metabolic activation system:

phenobarbital and 5,6-benzoflavone induced rat liver S9

Test concentrations with justification for top dose:

0.5, 1, 2, 5, 10, 20, 50%

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: HEPA filtered air
- Justification for choice of solvent/vehicle: none given in study report

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

air

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

TA 1535 without metabolic activation; 0.5 μg/plate

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

air

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide

Remarks:

TA 100 (0.01μg/plate), TA 98 (0.1 μg/plate) and E. coli (0.005 μg/plate), without metabolic activation

Controls 3

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

air

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

TA 1537, 80 μg/plate, without metabolic activation

Controls 4

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

air

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

all strains with metabolic activation (0.5 μg/plate TA 98; 1 μg/plate TA 100, 2 μg/plate other strains)

Details on test system and experimental conditions:

METHOD OF APPLICATION: other: the substance was prepared by mixing a volume of the gas with a fixed volume of air in a 10 l gas sampling bag (20-1 TEDLER bag).

DURATION

- Exposure duration: 24 hours with lids off; then removed, test substance allowed to evaporate for 20-30 minutes, covered and inverted and returned to the appropriate gas sampling bag and incubated for a further 24 hours.
- Expression time (cells in growth medium): 48 hours

SELECTION AGENT (mutation assays): histidine or tryptophan deficient agar.

NUMBER OF REPLICATIONS: duplicate plates; initial dose determination test was repeated in an independent main test.

DETERMINATION OF CYTOTOXICITY
- Method: other: condition of background lawn; number and size of revertant colonies

METABOLIC ACTIVATION: phenobarbital and 5,6-benzoflavone induced rat liver S9 was purchased from Kikkoman Co., containing 26.02 mg/ml protein. S9 mix contained 10% S9, and glucose-6-phosphae, NADP and NADPH as co-factors. 0.1 ml culture and 0.5 ml S9 were added to 2.0 ml of top agar, giving a final concentration of approximately 2% S9.

Evaluation criteria:

The test substance is considered to be mutagenic when a reproducible dose-related increase in the number of revertant colonies is observed and the number of revertant colonies per plate is more than twice that of the solvent control.

Statistics:

None

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

E. coli WP2

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS

- Precipitation: no precipitate was observed


COMPARISON WITH HISTORICAL CONTROL DATA: results were within the range of the historical controls

Any other information on results incl. tables

Table 1 Pre-incubation. Revertants per plate (mean of 2 plates)

Concentration (%)	TA 100		TA 1535		WP2 uvrA		TA 98		TA 1537
	- MA	+ MA	- MA	+ MA	- MA	+ MA	- MA	+ MA	- MA	+ MA
0*	105	114	14	13	77	90	21	28	8	10
0.05	99	103	12	15	75	100	20	23	8	10
0.1	98	116	13	9	66	103	14	20	11	9
0.5	101	96	17	11	64	101	14	26	3	8
1.0	101	105	15	11	69	93	14	27	5	10
5.0	104	118	15	12	79	97	14	23	7	6
10	109	102	14	10	64	91	16	22	6	10
50	98	87	15	15	64	75	12	22	8	5
Positive control	512	1373	355	283	595	1208	556	375	379	261

*Solvent control (air)

Table 2 Pre-incubation. Revertants per plate (mean of 2 plates)

Concentration (%)	TA 100		TA 1535		WP2 uvrA		TA 98		TA 1537
	- MA	+ MA	- MA	+ MA	- MA	+ MA	- MA	+ MA	- MA	+ MA
0*	104	107	11	11	63	91	14	21	8	9
0.5	92	112	8	6	78	89	13	20	5	9
1.0	97	108	10	6	73	92	17	23	5	5
2.0	94	124	11	8	57	78	14	22	10	6
5.0	100	106	6	7	66	99	13	19	4	7
10	108	116	12	9	71	99	18	21	6	7
20	75	103	8	8	61	90	12	22	4	6
50	85	80	6	8	58	79	18	16	6	7
Positive control	492	1147	329	263	857	1209	559	322	321	228

*Solvent control (air)

Applicant's summary and conclusion

Conclusions:

Trimethylsilane has been tested in a study conducted according to a national standard (Japanese) method that is similar to OECD 471, and in compliance with GLP. No increase in the number of revertants was observed in the presence or absence of metabolic activation when tested using the gas exposure method at concentrations up to 50%. The observations made in the initial dose-ranging study were reproduced in the main test. The strains tested were Salmonella typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2 uvrA / pKM101, and duplicate plates were used. Appropriate vehicle (air) and positive controls were used and gave expected responses; only 2-aminoanthracene was used as positive control with metabolic activation.