2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-04-02 to 2012-05-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: US EPA GLP Standards 40 CFR 792 (TSCA)

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane

EC Number:

219-154-7

EC Name:

2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane

Cas Number:

2374-14-3

Molecular formula:

C12H21F9O3Si3

IUPAC Name:

2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane

Constituent 2

Reference substance name:

002374-14-3

Cas Number:

002374-14-3

IUPAC Name:

002374-14-3

Test material form:

other: opaque solid

Test animals

Species:

mouse

Strain:

ICR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan, Frederick, MD
- Age at study initiation: 6 weeks old
- Weight at study initiation: 29.4 - 32.5 grams (male) and 23.9 - 28.8 grams (female)
- Assigned to test groups randomly: yes (based on equalization of group mean body weights)
- Housing: Five same sex per rodent Micro-Barrier cage
- Diet (e.g. ad libitum): yes
- Water (e.g. ad libitum): yes
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 72 +/- 3F
- Humidity (%): 50 +/- 20%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12 hour light/dark cycle

IN-LIFE DATES: From: To: 18 - 23 April 2012

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: corn oil
- Justification for choice of solvent/vehicle: based on Sponsor information
- Concentration of test material in vehicle:
- Amount of vehicle (if gavage or dermal): 80%
- Type and concentration of dispersant aid (if powder):
- Lot/batch no. (if required):
- Purity:

Duration of treatment / exposure:

24 and 48 hours

Frequency of treatment:

Test compounds and controls were administered by a single oral gavage at a dose volume of 10mL/kg body weight.

Post exposure period:

Negative and positive controls and all three dose levels were sacrificed at 24 hours after administration of test substance. The vehicle control and highest dose level were sacrificed 48 hours after administration of test substance.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

500 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

1 000 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

2 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

Five

Control animals:

yes, concurrent vehicle

Positive control(s):

- cyclophosphamide
- Justification for choice of positive control(s): standard guideline positive control
- Route of administration: oral gavage
- Doses / concentrations: 50 mg/kg

Examinations

Tissues and cell types examined:

Bone marrow was collected from all treatment groups and polychromatic erythrocytes (PCE's) and normochromatic erythrocytes (NCE's) were examined for micronuclei.

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION: limit dose

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields): no further information

DETAILS OF SLIDE PREPARATION: Following euthanasia, the femurs were exposed, and the bone marrow was aspirated into syringe with foetal bovine serum. The bone marrow was centrifuged and the supernatant drawn off. The cell pellet was re-suspended and a small drop of bone marrow suspension was spread onto a clean glass slide (2 slides per mouse). The slides were air dried, fixed in methanol and stained with acridine orange.

METHOD OF ANALYSIS: Slides were coded randomly. Bone marrow cells were evaluated using a fluorescent microscope. 2000 polychromatic erythrocytes (PCEs) were scored for micronuclei per animal. The number of normochromatic erythrocytes (NCEs) and micronucleated NCEs (MNCEs) in the field of 1000 total erythrocytes was determined. The proportion of PCEs to total erythrocytes (ECs) was also determined per 1000 erythrocytes for each animal.

Evaluation criteria:

The test article would have been considered to induce a positive response if the incidence of micronucleated polychromatic erythrocytes at one or more doses is statistically elevated relative to the vehicle control, in a dose dependent manner and exceeding the range of historical vehicle controls.

Statistics:

Statistical significance was determined using the Kastenbaum-Bowman tables which are based on the binomial distribution. All analyses were performed separately for each sex and sampling time.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Remarks:

on PCE/EC ratios

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

RESULTS OF DETERMINATION OF SYSTEMIC AVAILABILITY:
All animals survived until post-dose collection time point.
Dose concentration, stability and homogeneity were verified by GC/FID methods. The dose solution concentrations were determined to be within the criteria for acceptance, and to be stable for at least two days at room temperature. No extraction of the solutions was carried out prior to determining concentration.
The limit of quantitation of the GC/MS determination of test article content in plasma was 14.4 ng/g. Test article detected in plasma was significantly above the limit of detection for all dose groups at both blood collection time points.
Necroscopy: gross lesions were noted in one animal in the low dose group, these were not attributed to the test article. No gross lesions were observed in any other animal.

Any other information on results incl. tables

Summary of Bone Marrow Micronucleus Analysis

Treatment (10 ml/kg)	Sex and time (hrs)	Mean of PCE/Total erythrocytes	Mean of MPCE/1000 PCE	Number of MPCE/PCE scored
Solvent control	M - 24	0.576	0.2	2 / 1000
	F -24	0.574	0.4	4 / 1000
500 mg/kg bw	M - 24	0.556	0.5	5 / 1000
	F - 24	0.563	0.2	2 / 1000
1000 mg/kg bw	M - 24	0.412	0.2	2 / 1000
	F - 24	0.587	0.4	4 / 1000
2000 mg/kg bw	M - 24	0.522	0.2	2 / 1000
	F - 24	0.568	0.5	5 / 1000
Positive control	M - 24	0.500	24.4	**244 / 1000
	F - 24	0.488	18.0	**180 / 1000
Solvent control	M - 48	0.579	0.2	2 / 1000
	F - 48	0.582	0.3	3 / 1000
2000 mg/kg bw	M - 48	0.447	0.6	6 / 1000
	F - 48	0.426	0.3	3 / 1000

** Statistically significant increase compared to vehicle control

Applicant's summary and conclusion

Conclusions:

2,4,6-Trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane was tested in an in vivo mouse micronucleus assay conducted according to OECD Test Guideline 474 and in compliance with GLP. No evidence of test substance related induction of micronucleus was observed after oral administration by gavage at doses of 500, 1000 and 2000 mg/kg bw. No test substance related changes in the PCE/NCE ratio were observed, so it was concluded that the test substance did not inhibit erythropoiesis. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is not genotoxic under the conditions of the test.