Decamethylcyclopentasiloxane

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Decamethylcyclopentasiloxane

EC Number:

208-764-9

EC Name:

Decamethylcyclopentasiloxane

Cas Number:

541-02-6

Molecular formula:

C10H30O5Si5

IUPAC Name:

2,2,4,4,6,6,8,8,10,10-decamethyl-1,3,5,7,9,2,4,6,8,10-pentoxapentasilecane

Method

Species / strain

Species / strain 1

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain 2

Species / strain / cell type:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital beta-naphthoflavone induced rat liver S9

Test concentrations with justification for top dose:

33, 100, 333, 1000, 2500 and 5000 μg/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Ethanol

- Justification for choice of solvent/vehicle: the solvent was chosen because of its solubility properties and relative non-toxicity to bacteria, and on request of the sponsor.

Controls

Controls 1

Untreated negative controls:

yes

Remarks:

untreated

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

All strains (with activation)

Controls 2

Untreated negative controls:

yes

Remarks:

untreated

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-nitro-o-phenylene-diamine

Remarks:

TA 98, TA 1537 (without activation)

Controls 3

Untreated negative controls:

yes

Remarks:

untreated

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

TA 100, TA 1535 (without activation)

Controls 4

Untreated negative controls:

yes

Remarks:

untreated

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

WP2uvrA (without activation)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation); preincubation

DURATION

- Preincubation period: 60 minutes

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

NUMBER OF REPLICATIONS: 3 plates for each test concentration

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth; background lawn

Evaluation criteria:

The test article is considered a mutagen if a biologically relevant increase in the number of revertants exceeding the threshold of twice (strains TA-98, TA-100 and WP2 uvrA) or thrice (strains TA-1535, TA-1537) the colony count of the corresponding solvent control is observed. An increase exceeding the threshold at only one concentration is judged as biologically relevant if produced in an independent second experiment. A dose dependent increase is considered biologically relevant if the threshold is exceeded at more than one concentration. A dose dependent increase in the number of revertant colonies below the threshold is regarded as an indication of a mutagenic potential if reproduced in an independent second experiment. However, whenever the colony counts remain within the historical range of the negative and solvent controls such an increase is not considered biologically relevant.

Statistics:

No statistical evaluation is required. Responses (number of revertants) to the test article were compared to concurrent
negative and positive controls.

Results and discussion

Test results

Test results 1

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:

valid

Positive controls validity:

valid

Test results 2

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:

valid

Positive controls validity:

valid

Additional information on results:

No substantial increase in revertants colony numbers of any the five tester strains was observed following treatment with D5 at any dose level, either in the presence or absence of metabolic activation. Appropriate reference mutagens were used as positive controls and showed a distinct increase of induced revertant colonies. The controls were within historical values with the following exceptions: Strain TA 1535 without activation: number of revertants greater than historical values; small deviations were observed in the negative controls of two strains in the second experiment. These deviations do not affect the validity of the experiment.

Any other information on results incl. tables

Table 1 Experiment 1 plate incorporation: Number of revertants per plate (mean of 3 plates)

	TA 1535			TA 1537			TA 98
Conc. µg/plate	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Untreated	16	17	no	6	21	no	27	32	no
0*	13	27	no	8	15	no	28	44	no
33	13	14	no	5	13	no	30	41	no
100	14	17	no	5	11	no	32	42	no
333	10	18	no	7	16	no	34	42	no
1000	15	14	no	9	15	no	30	40	no
2500	14	16	no	7	11	no	33	39	no
5000	16	13	no	8	13	no	36	33	no
Positive control	884	161	-	58	67	-	273	658	-

*solvent control with ethanol

 

 Table 2 Experiment 1 plate incorporation: Number of revertants per plate (mean of 3 plates)

	TA 100			E coli WP2 uvrA
Conc. µg/plate	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Untreated	162	178	no	35	42	no
0*	152	164	no	40	47	no
33	166	194	no	38	36	no
100	156	190	no	45	39	no
333	151	215	no	35	43	no
1000	148	207	no	35	47	no
2500	164	206	no	26	46	no
5000	144	190	no	31	47	no
Positive control	773	970	-	768	180	-

*solvent control with ethanol

 

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

	TA 1535			TA 1537			TA 98
Conc. µg/plate	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Untreated	18	16	no	8	15	no	33	40	no
0*	15	21	no	9	12	no	38	48	no
33	11	17	no	11	14	no	32	39	no
100	16	20	no	10	9	no	34	46	no
333	21	19	no	8	15	no	40	48	no
1000	18	17	no	11	13	no	41	47	no
2500	15	15	no	9	10	no	40	48	no
5000	16	14	no	8	11	no	43	55	no
Positive control	1319	147	-	72	64	no	229	507	-

*solvent control with ethanol

 

 Table 4 Experiment 2 preincubation: Number of revertants per plate (mean of 3 plates)

	TA 100			E coli WP2 uvrA
Conc. µg/plate	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Untreated	178	248	no	38	31	no
0*	206	287	no	44	37	no
33	191	265	no	32	49	no
100	187	251	no	38	51	no
333	213	244	no	41	46	no
1000	185	239	no	36	38	no
2500	217	269	no	39	35	no
5000	229	318	no	47	43	no
Positive control	581	624	-	284	166	-

*solvent control with ethanol

Applicant's summary and conclusion

Conclusions:

Decamethylcyclopentasiloxane has been tested according to OECD 471 and in compliance with GLP using Salmonella typhimurium strains TA 1535, TA 1537, TA 98 and TA 100 and Escherichia coli WP2 uvrA. No test-substance related increase in the number of revertants was detected in the presence or absence of metabolic activation in either the initial (RCC Cytotest cell research, 2003) plate incorporation assay or the repeat experiment using pre-incubation, up to limit concentrations. Appropriate positive, solvent and untreated controls were included and gave expected results. The test substance is therefore considered to be negative for mutagenicity to bacteria under the conditions of the test.