1,1,1,3,5,5,5-heptamethyltrisiloxane

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:

2008-01-28 - 2008-02-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1997

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

1,1,1,3,5,5,5-heptamethyltrisiloxane

EC Number:

217-496-1

EC Name:

1,1,1,3,5,5,5-heptamethyltrisiloxane

Cas Number:

1873-88-7

Molecular formula:

C7H22O2Si3

IUPAC Name:

1,1,1,3,5,5,5-heptamethyltrisiloxane

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/β-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: acetone
- Justification for choice of solvent: the solvent was chosen because of its solubility properties and its relative non-toxicity to the bacteria.

Controls

Controls 1

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

TA1535 and TA100 without metabolic activation 10 µg/plate

Controls 2

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-nitro-o-phenylene-diamine (4-NOPD)

Remarks:

TA98 - 10 µg/plate, TA1537 - 50 µg/plate without metabolic activation

Controls 3

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

WP2 uvrA without metabolic activation 3 µl/plate

Controls 4

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene (2-AA)

Remarks:

TA1535, TA1537, TA98, TA100 - 2.5 µg/plate and WP2 uvrA - 10 µg/plate with metabolic activation

Details on test system and experimental conditions:

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

ACTIVATION: S9 mix contained glucose-6-phophate and NADP as co-factors, the S9 supernatant was 10% v/v in the S9 mix of which 0.5 ml were added to 2 ml top agar, giving a final concentration of approximately 2% S9.

DURATION
- Preincubation period: 60 minutes at 37ºC
- Exposure duration: Experiment 1 - 72 hours at 37ºC, experiment II - 72 hours at 37ºC + a further 72 hours at 4ºC


SELECTION AGENT: histidine deficient agar

NUMBER OF REPLICATIONS: triplicate plates, experiment repeated

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

Evaluation criteria:

A result is considered as a mutagen if a biologically relevant increase in the number of revertants exceeding the threshold of twice (strains TA98, TA100 and WP2 uvrA) or thrice (strains TA1535 and TA1537) the colony count of the corresponding solvent control is observed. A dose dependent increase is considered biologically relevant if the threshold is exceeded at more than one concentration. An increase exceeding the threshold at only one concentration is judged as biologically relevant if reproduced in an independent second experiment.

Statistics:

No statistical analysis was performed.

Results and discussion

Test results

Key result

Species / strain:

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

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:

TEST-SPECIFIC CONFOUNDING FACTORS

COMPARISON WITH HISTORICAL CONTROL DATA: yes, included in report and all within limits

Any other information on results incl. tables

Results of plate incorporation assay Experiment I; revertants per plate (mean of 3 plates)

[Note, the pre-experiment is reported as Experiment 1, as there were evaluable plates at all concentrations in all strains used.]

Dose level (µg/plate)	Metabolic activation	Mean revertant colony counts
		TA 1535	TA 1537	TA 98	TA 100	WP2 uvrA
Solvent control**	-	16	13	22	130	54
Negative control***	-	14	12	24	130	47
3	-	11	14	21	138	50
10	-	11	14	29	130	46
33	-	11	12	21	122	51
100	-	9	14	25	120	45
333	-	16	18	21	136	52
1000	-	15	10	24	138	52
2500	-	15	13	22	137	59
5000	-	13	8	26	158	62
Positive control	-	1935	78	281	2196	1314
Solvent control**	+	15	16	33	172	64
Negative control***	+	18	13	37	154	49
3	+	17	16	33	149	64
10	+	17	15	35	165	57
33	+	17	16	34	177	65
100	+	18	17	38	165	61
333	+	18	18	35	161	64
1000	+	12*	15*	29*	157*	55*
2500	+	11*	13*	25*	156*	55*
5000	+	12*	11*	26*	148*	55*
Positive control	+	234	123	998	1334	231

* non-interfering precipitate

** with acetone

*** Untreated

Results of preincubation assay, Experiment 2; revertants per plate (mean of 3 plates)

 

Dose level µg/plate	Metabolic activation	Mean revertant colony counts
		TA 1535	TA 1537	TA 98	TA 100	WP2 uvrA
Solvent control**	-	12	12	30	133	37
Negative control***	-	14	17	30	120	44
33	-	13	13	23	136	42
100	-	14	11	23	135	45
333	-	15	13	31	125	46
1000	-	15	12	26	133	43
2500	-	15	11	21	118	39
5000	-	14	10	31	125	38
Positive control	-	2143	99	335	1941	901
Solvent control**	+	19	15	34	121	60
Negative control***	+	16	18	33	156	49
33	+	18	17	31	142	52
100	+	15	19	33	142	52
333	+	16	19	36	137	60
1000	+	18*	16*	30*	129	60
2500	+	15*	16*	30*	135*	56*
5000	+	17*	14*	30*	154*	49*
Positive control	+	307	195	1206	863	349

 

* non-interfering precipitate

** with acetone

*** Untreated

Applicant's summary and conclusion

Conclusions:

1,1,1,3,5,5,5-heptamethyltrisiloxane has been tested for mutagenicity to bacteria in a study which was conducted according 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 initial plate incorporation assay or the repeat experiment using the preincubation method. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.