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:
2000-11-27 to 2001-01-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
mouse
Strain:
NMRI
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS

- Source: Harlan Winkelman (D-33178, Borchen)

- Weight at study initiation: 24 - 42 g

- Assigned to test groups randomly: yes, under following basis: assigned and tail tagged by chance

- Housing: Macrolon Type III (Hereto, D-79302 Emmendingen)

- Diet (e.g. ad libitum): ad libitum

- Water (e.g. ad libitum): ad libitum

- Acclimation period: minimum of 5 days


ENVIRONMENTAL CONDITIONS

- Temperature (°C): 19 - 25 ˚c

- Humidity (%): 49.5 - 61 %

- Photoperiod (hrs dark / hrs light): 12 hrs dark / 12 hrs light


IN-LIFE DATES: From: To: 15 January 2001

Administration / exposure

Route of administration:
oral: unspecified
Vehicle:
- Vehicle(s)/solvent(s) used: CMC (carboxymethyl cellulose)

- Justification for choice of solvent/vehicle: The vehicle was chosen because it is relatively non toxic to the test animals

- Lot/batch no. (if required): 36H0738
Details on exposure:
Route of exposure: Oral
Duration of treatment / exposure:
24 - 48 hours
Frequency of treatment:
The animals received the test item once orally.
Post exposure period:
Animals were sacrificed 24 - 48 h after treatment.
Doses / concentrations
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

- Doses / concentrations: 10 ml/kg bw of 0.9 % solution in 0.9 % NaCl

Examinations

Tissues and cell types examined:
Bone marrow
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: centrifuged cells were suspended in a thin layer of FCS and smeared on a slide. The smears were air dried and stained with May-Grunwald (Merck, D-64293 Darmstadt) / Giemsa (Merck, D-64293 Darmstadt).

METHOD OF ANALYSIS: microscopic examination. 2000 PCE scored for incidence of polychromatic erythrocytes with micronuclei. Ratio of PCE / NCE was scored based on 1000 erythrocytes (PCE+NCE)
Evaluation criteria:
A test item is classified as mutagenic if it induces either a statistically significant dose related increase in the number of micronucleated polychromatic erythrocytes or a reproducible statistically significant positive response for at least one of the test points.
Statistics:
Micronuclei in 2000 PCE per animal were counted for each sex. NCE per 1000 PCE, Sum and Mean calculated for each sex.

Results and discussion

Test results
Key result
Sex:
male/female
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
See table 3

RESULTS OF DEFINITIVE STUDY

- Induction of micronuclei (for Micronucleus assay): negative

- Ratio of PCE/NCE (for Micronucleus assay): see table 3. The PCE/NCE ratio was unchanged in treated animals, so there is no evidence that the test substance reached the target tissue.

- Appropriateness of dose levels and route: appropriate dose and route

- Statistical evaluation: no statistically significant induction of micronuclei occurred.

Any other information on results incl. tables

Table 3: Results of in vivo micronucleus test

 

Vehicle

Control

Positive

Control

200 mg/kg

bw

1000 mg/kg

bw

2000 mg/kg

bw

2000 mg/kg

bw

Number of cells evaluated

2000

2000

2000

2000

2000

2000

Sampling time (h)

24

24

24

24

24

48

Number of erythrocytes

normo­chromatic

NR

NR

NR

NR

NR

NR

poly­chromatic

2000

2000

2000

2000

2000

2000

polychromatic with micronuclei

7 Male

5.2 Female

70.2 Male

42.4 Female

7.6 Male

9.2 Female

8.4 Male

4.8 Female

9.4 Male

5.0 Female

7.4 Male

4.8 Female

Ratio of erythrocytes

polychromatic / normochromatic

Male

1000/679.4

Female

1000/766.6

Male

1000/608

Female

1000/657.6

Male

1000/712.4

Female

1000/655.8

Male

1000/656.4

Female

1000/611.6

Male

1000/657

Female

1000/641.2

Male

1000/1064.6

Female

1000/511

polychromatic with micro­nuclei / normochromatic

NR

NR

NR

NR

NR

NR

 

Applicant's summary and conclusion

Conclusions:
Triethoxy(2,4,4-trimethylpentyl)silane has been tested in a reliable in vivo mouse micronucleus assay according to OECD 474 and under GLP. No statistically significant increase in the number of cells with micronuclei was observed after oral administration of the limit dose of 2000 mg/kg bw. Appropriate positive and vehicle controls were included and gave expected results. The PCE / NCE ratio was slightly affected in treated males, indicating that the test item was of low toxicity to the target tissue. It is concluded that the test substance is negative for the induction in micronuclei under the conditions of the test.