Octamethylcyclotetrasiloxane

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The range of strains used does not comply with current guidelines

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Reference 2

Reference Type:

publication

Title:

No information

Author:

Vergnes et al.

Year:

2000

Bibliographic source:

Environ. Molec. Mutagen. 36, 13-21

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1983

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: EPA Fed Reg 50, 51, 51 (1987)

Principles of method if other than guideline:

preincubation method

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Octamethylcyclotetrasiloxane

EC Number:

209-136-7

EC Name:

Octamethylcyclotetrasiloxane

Cas Number:

556-67-2

Molecular formula:

C8H24O4Si4

IUPAC Name:

2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane

Method

Species / strain

Species / strain / cell type:

S. typhimurium, other: TA98, TA100, TA1535, TA1537, TA1538

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254-induced rat liver S9 

Test concentrations with justification for top dose:

0.0003 - 5.0 mg/plate (10 concentrations, cytotoxicity test); 0.1-5.0 mg/plate (5 concentrations, mutagenicity test)

Vehicle / solvent:

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

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-nitro-phenylenediamine

Remarks:

TA 98 and TA 1538 without activation

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

TA 1537 without activation

Controls 3

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

TA 100 and TA 1535 without activation

Controls 4

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

all strains with activation

Details on test system and experimental conditions:

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

DURATION
- Preincubation period: 20 minutes
- Exposure duration: 48-72 hours
- Expression time (cells in growth medium): 48-72 hours


NUMBER OF REPLICATIONS: triplicate


DETERMINATION OF CYTOTOXICITY
- Method: other: growth of background lawn, number of revertants

METABOLIC ACTIVATION
S9 homogenate from Aroclor 1254-induced rats was obtained from Microbiological associates, Bethesda, Maryland, and checked for activity with 7,12-dimethylbenzanthracene. S9 mix included 8 mM MgCl2, 33 mM KCl, 5 mM glucose-6-phophate, 4 mM NADP. 100 mM sodium phosphate pH 7.4, and S9. Amount of S9 was based on activity with 7,12-dimethylbenzanthracene.

Evaluation criteria:

A dose-related increase in the mean reversion frequency compared to solvent control in at least one strain was considered positive if at least one dose produced at least twice the reversion frequency of the solvent control

Statistics:

Mean an standard deviation of replicate plates

Results and discussion

Test results

Key result

Species / strain:

other: Salmonella typhimurium TA98, TA100, TA1535, TA1537, TA1538

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:

not applicable

Positive controls validity:

valid

Any other information on results incl. tables

Concurrent sterility testing indicated that the test substance, the S9 mix, and all solvent and control agents were sterile.

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

Conc. (µl/ml)	TA 98			TA 100			TA 1535
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
0*	18	27	No	108	112	No	15	18	No
100	20	34	No	105	131	No	17	20	No
300	17	30	No	127	109	No	16	15	No
1000	29	27	No	123	116	No	18	18	No
3000	24	27	No	117	109	No	16	18	No
5000	20	31	No	125	112	No	18	16	No
Positive control	431	1216	-	933	1780	-	1033	15	-

*solvent control with ethanol

 

 

Table 1b : Experiment 1 Plate incorporation Number of revertants per plate

Conc. (µl/ml)	TA 1537			TA 1538
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
0*	13	6	No	9	17	No
100	9	12	No	8	16	No
300	9	7	No	12	24	No
1000	8	10	No	9	17	No
3000	7	9	No	6	20	No
5000	10	7	No	7	13	No
Positive control	118	169	-	924	1259	-

*solvent control with ethanol

 

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

Conc. (µl/ml)	TA 98			TA 100			TA 1535
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
0*	21	31	No	126	117	No	12	15	No
100	21	23	No	119	111	No	11	14	No
300	22	32	No	110	122	No	16	19	No
1000	19	21	No	105	91	No	15	14	No
3000	22	22	No	123	97	No	9	11	No
5000	13	26	No	107	102	No	12	14	No
Positive control	680	1038	-	942	2249	-	942	153	-

*solvent control with ethanol

 

 

Table 2b : Experiment 2 Plate incorporation Number of revertants per plate

Conc. (µl/ml)	TA 1537			TA 1538
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
0*	7	9	No	7	16	No
100	8	6	No	5	14	No
300	7	5	No	9	12	No
1000	9	6	No	9	16	No
3000	8	6	No	9	13	No
5000	8	8	No	8	16	No
Positive control	282	337	-	715	1364	-

*solvent control with ethanol

Applicant's summary and conclusion

Conclusions:

Octamethylcyclotetrasiloxane has been tested under GLP according to OECD 471 (1983). No increase in the number of reversions was observed. The test substance is considered to be negative for mutagenicity in bacteria under the conditions of the test.