Registration Dossier

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
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
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
yes
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Test material form:
other: liquid

Test animals

Species:
mouse
Strain:
ICR
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan, Frederick, MD
- Age at study initiation: 6 weeks old
- Weight at study initiation: 27.7 - 34.9 grams for males and 24.4 -29.5 grams for females
- Assigned to test groups randomly: [yes, under following basis: ] 5 males and 5 females per test group
- Fasting period before study: no
- Housing: 5 mice per sex per approved Micro-Barrier cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 days

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

IN-LIFE DATES: 6 weeks of age on 11th April 2012 To: 26th 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:
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: appropriate amount of test substance weighed and combined with 80% target volume of vehicle. After vortexing, remaining volume of vehicle was added. Dosing solutions were 100, 200 and 400 mg/ml
Duration of treatment / exposure:
Negative and positive controls and all treatment groups - 24 hour. Negative control and highest treatment group - 48 hours.
Frequency of treatment:
Test compound and controls were dosed once by oral gavage.
Post exposure period:
The negative and positve controls and treatment groups were sacrificed 24 hours after administration of test substance. The negative control and highest treatment group were sacrificed 48 after administration of test substance.
Doses / concentrationsopen allclose all
Dose / conc.:
500 mg/kg bw/day (nominal)
Remarks:
dosing formulations were analysed: 200 and 400 mg/ml solutions met acceptance criteria (85-115% of target concentration; 100 mg/ml solution was below this range (~84.5%)
Dose / conc.:
1 000 mg/kg bw/day (nominal)
Remarks:
dosing formulations were analysed: 200 and 400 mg/ml solutions met acceptance criteria (85-115% of target concentration; 100 mg/ml solution was below this range (~84.5%)
Dose / conc.:
2 000 mg/kg bw/day (nominal)
Remarks:
dosing formulations were analysed: 200 and 400 mg/ml solutions met acceptance criteria (85-115% of target concentration; 100 mg/ml solution was below this range (~84.5%)
No. of animals per sex per dose:
5 males and 5 females
Control animals:
yes, concurrent vehicle
Positive control(s):
- positive control substance: 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 marrrow was collected from all treatment groups and polychromatic erythrocytes (PCE's), 2000 were scored per animal thus 10,000 per treatment group, and normochromatic erythrocytes (NCE's) were examined for micronuclei.
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION: dose limit

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 fetal 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 spead 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 flourescent microscope. 2000 PCE's were scored for micronuclei per animal. The corresponding NCE's were scored for micronuclei.


OTHER:
Evaluation criteria:
The test substance is considered to induce a positive response if the incidence of micronucleated polychromatic erythrocytes at one or more doses is statistically elevated elative compared to the vehicle control.
Statistics:
Statistical significance was determined using the Kastenbaum-Bowman tables which are based on the binomial distribution.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
not examined
Remarks:
No mortalities occurred. Diarrhea noted in one male mouse at 1000 mg/kg bw; piloerection noted in some male and all female, and diarrhea noted in 2 males and 2 females in 2000 mg/kg bw group
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid

Any other information on results incl. tables

Summary of Bone Marrow Micronucleus Analysis

Treatment (5 ml/kg bw)

Sex and time (hrs)

Mean of PCE/Total erythrocytes

Mean of MPCE/2000 PCE

Number of MPCE/PCE scored

Solvent control

M - 24

0.538

0.0

0 / 1000

F -24

0.546

0.1

1 / 1000

500 mg/kg bw

M - 24

0.531

0.1

1 / 1000

F - 24

0.566

0.2

2 / 1000

1000 mg/kg bw

M - 24

0.585

0.6

6 / 1000

F - 24

0.561

0.3

3 / 1000

2000 mg/kg bw

M - 24

0.567

0.2

2 / 1000

F - 24

0.574

0.1

1 / 1000

Positive control

M - 24

0.472

23.3

*233 / 1000

F - 24

0.462

15.5

*155 / 1000

Solvent control

M - 48

0.433

0.3

3 / 1000

F - 48

0.544

0.2

2 / 1000

2000 mg/kg bw

M - 48

0.527

0.1

1 / 1000

F - 48

0.581

0.0

0 / 1000

 

* = Statistically significant increase compared to vehicle control

PCE: polychromatic erythrocytes; MPCE; micronucleated PCE

Applicant's summary and conclusion

Conclusions:
1,1,3,3-Tetramethyl-1,3-divinyldisiloxane was tested in an in vivo mouse micronucleus assay according to OECD TG 474, in compliance with GLP. No evidence of a test substance related increase in the induction of micronucleus was observed after dosing orally by gavage at 500, 1000 and 2000 mg/kg bw. Appropriate positive and vehicle controls were included and gave expected results. Confirmation of test article exposure was provided by an oral gavage study to determine concentration of test article in the plasma. It is concluded that the test substance is not genotoxic under the conditions of the test.