Dichlorocyclohexylmethylsilane

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:

9-Apr-1987 to 21-Aug-1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The restrictions were that the number of erythrocytes scored for the detection of micronucleus was not in accordance with the current guideline and the administered dose exceeded the recommended limit dose for this assay.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

(old guideline)

Deviations:

yes

Remarks:

: only 1000 PCE's per animal examined instead of the 2000 required by current regulation.

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Cyclohexylmethyldimethoxysilane

IUPAC Name:

Cyclohexylmethyldimethoxysilane

Constituent 2

Reference substance name:

Cyclohexyldimethoxymethylsilane

EC Number:

402-140-1

EC Name:

Cyclohexyldimethoxymethylsilane

Cas Number:

17865-32-6

Molecular formula:

C9H20O2Si

IUPAC Name:

Cyclohexyl-dimethoxy-methylsilane

Test animals

Species:

mouse

Strain:

CD-1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:Charles River Italia S.p.A., Calco, Italy
- Weight at study initiation: 28-37g (males), 24-33g (females)
- Assigned to test groups randomly: no data
- Fasting period before study: overnight
- Acclimation period: 5 days

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: corn oil

Duration of treatment / exposure:

Single exposure.

Frequency of treatment:

Single administration.

Post exposure period:

Animals were sacrificed at 24, 48 and 72 hours after treatment.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

10 other: mL/kg (nominal)

Remarks:

vehicle

Doses / concentrations 2

Dose / conc.:

2 500 mg/kg bw/day (nominal)

Remarks:

test material

Doses / concentrations 3

Dose / conc.:

5 000 mg/kg bw/day (nominal)

Remarks:

test material

Doses / concentrations 4

Dose / conc.:

5 mg/kg bw/day (nominal)

Remarks:

Mitomycin C

No. of animals per sex per dose:

5 male, 5 female

Control animals:

yes, concurrent vehicle

Positive control(s):

Mitomycin C in sterile distilled water was prepared immediately prior to dosing.

Examinations

Tissues and cell types examined:

After sacrifice, the femurs were removed and marrow cells obtained by flushing with foetal calf serum.

Details of tissue and slide preparation:

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields): 24, 48, 72 hours

DETAILS OF SLIDE PREPARATION: The removed marrow cells obtained by flushing with foetal calf serum were centrifuged and a concentrated suspension prepared to make smears on slides. These slides were air - dried overnight and then stained with May-Gruenwald and Giemsa, and mounted with Eukitt. Three slides were made from each animal.

METHOD OF ANALYSIS: The slides were examined under medium magnification and one slide from each animal was selected according to staining and quality of smears. Where the toxicity of the test substance was not so great as to inhibit cell proliferation, at least 1000 PCEs were examined at high magnification (x1000) for the presence or absence of micronuclei. At the same time the number of normochromatic erythrocytes was also recorded.

Statistics:

The incidence of micronucleated cells per 1000 erythrocytes (mature or polychromatic) are given as group means by sex, and for the sexes combined. The standard error of the means and rages are also shown. The animals presenting less than 200 PCEs per 1000 NCEs scored were excluded from the calculations and subsequent statistical analyses.

Results and discussion

Test results

Test results 1

Key result

Sex:

male

Genotoxicity:

positive

Remarks:

at 48 hours increase in micronucleated PCEs at high dose level.

Toxicity:

yes

Vehicle controls validity:

not specified

Negative controls validity:

not specified

Positive controls validity:

valid

Test results 2

Key result

Sex:

female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

not specified

Negative controls validity:

not specified

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
In preliminary toxicity trials it was established that treatment with Cyclo-hexyl-dimethoxy-silane at 5000 mg/kg by oral gavage did not result in excessive lethality, and accordingly dose-levels of 5000 and 2500 mg/kg were selected for this study. The oral route of administration was used in this study on the instruction of the Sponsor.

RESULTS OF DEFINITIVE STUDY
- Induction of micronuclei (for Micronucleus assay):
- Ratio of PCE/NCE (for Micronucleus assay): A dose related increase in the ration of mature to polychromatic erythrocytes was observed at the 48 hour sampling time in the test substance treatment groups. Similar increases were observed at the 24 hour sampling time. This indicates that the treatment with the test substance exerted an inhibitory effect on cell division of bone marrow erythropoietic cells. The ratio of mature to polychromatic erythrocytes increased at all sampling times following treatment with the positive control compound., indicating that this treatment resulted in inhibition of the cell division of the bone marrow erythropoietic cells.

Any other information on results incl. tables

Table 1:Results of in vivo micronucleustest at 24 hours (both sexes combined)

		Positive control 5 mg/kg	0 mg/kg	2500 mg/kg	5000 mg/kg
Number of cells evaluated		1000	1000	1000	1000
Number of erythro-cytes	normo­chromatic	12675	11579	13891	12003
	poly­chromatic	9449	10070	9464	8948
	polychromatic with micronuclei	23.1 ± 2.9	1.4±0.5	1.6± 0.5	1.9±0.6
Ratio of erythro­cytes	polychromatic / normochromatic	1.39	1.15	1.52	1.45

 Table 2:Results of in vivo micronucleus test at 48 hours (females)

		Positive control 5 mg/kg	0 mg/kg	2500 mg/kg	5000 mg/kg
Number of cells evaluated		1000	1000	1000	1000
Number of erythro-cytes	normo­chromatic	5219	3467	7110	7206
	poly­chromatic	3080	5062	4426	3770
	polychromatic with micronuclei	11.3±3.5	1.4±0.7	2.3±0.8	1.8±1
Ratio of erythro­cytes	polychromatic / normochromatic	2.12	0.69	1.69	2.2

Table 3:Results of in vivo micronucleus test at 48 hours (males)

		Positive control 5 mg/kg	0 mg/kg	2500 mg/kg	5000 mg/kg
Number of cells evaluated		1000	1000	1000	1000
Number of erythro-cytes	normo­chromatic	3632	5609	4450	5387
	poly­chromatic	1610	5000	4013	3600
	polychromatic with micronuclei	16.1±1.3	1.6±0.6	1.5±0.6	5.6±2.2
Ratio of erythro­cytes	polychromatic / normochromatic	2.84	1.12	1.11	2.02

 

Table 4:Results of in vivo micronucleustest at 72 hours (both sexes combined)

		Positive control 5 mg/kg	0 mg/kg	2500 mg/kg	5000 mg/kg
Number of cells evaluated		1000	1000	1000	1000
Number of erythro-cytes	normo­chromatic	8856	9861	8041	8617
	poly­chromatic	5567	9016	9579	7000
	polychromatic with micronuclei	4±0.9	2±0.2	1.7±0.5	1.4±0.4
Ratio of erythro­cytes	polychromatic / normochromatic	1.91	1.09	1.23	1.91

 

Applicant's summary and conclusion

Conclusions:

There was an increase in micronuclei 48 hours after dose administration, but only at a dose which exceeds the limit dose recommended for this assay, and only in male mice, not in female. No statistically significant increase was found when the results for male and female mice were combined. Considerable toxicity to bone marrow was observed and the number of polychromatic erythrocytes (PCEs) scored was only 3600 for the group, whereas it should have been 4000 per animal according to current guideline. The increase in micronuclei was observed in just one male animal (1000 cells scored for this animal). In view of the low number of cells scored, the negative result when results for male and female animals were combined, and the negative result from the in vivo rodent dominant lethal assay, indicating lack of cytogenicity in germ cells, the conclusion of negative for the in vivo micronucleus study is reasonable. The study was conducted in accordance to OECD 474 with deviations, and compliant with GLP..