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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Not GLP, but key cytogenetic parameters measured comparable to guideline study.

Data source

Reference
Reference Type:
publication
Title:
Dose-related clastogenic effects induced by benzene in bone marrow cells and in differentiating spermatogonia of Swiss CD1 mice.
Author:
Ciranni R, Barale R and Adler I-D.
Year:
1991
Bibliographic source:
Mutagenesis 6 (5), 417-421

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)
Deviations:
yes
Remarks:
only 3-4 animals/group
Principles of method if other than guideline:
Mice given single oral gavage dose of benzene (1 mL/kg bw) and chromosomal aberrations in bone marrow and spermatogonal cells assessed at time points up to 48 h post-treatment.
GLP compliance:
not specified
Type of assay:
other: bone marrow chromosome aberration assay and mammalian germ cell cytogenetic assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): benzene
- Source: Farmitalia, Carlo Erba, Italy

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River, Valco Co., Italy
- Age at study initiation: 2 months
- Weight at study initiation: 30-35 g
- no further details

ENVIRONMENTAL CONDITIONS
- no data

IN-LIFE DATES:
- no data

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Olive oil
Duration of treatment / exposure:
Single oral dose
Frequency of treatment:
Single oral dose
Post exposure period:
Up to 48 h
Doses / concentrations
Remarks:
Doses / Concentrations:
1 mL/kg
Basis:
actual ingested
No. of animals per sex per dose:
3-4 male mice
Control animals:
yes, concurrent vehicle

Examinations

Tissues and cell types examined:
Bone marrow and spermatogonal cells
Statistics:
The binomial dispersion test was applied to test homogeneity of results from control animals. Statistical differences between treated and solvent control groups were determined by Fisher's exact test. To compare the sensitivity of the two cell types the doubling doses were calculated. The doubling dose (DD) is defined as the dose that induces as many aberrations as occur spontaneously per cell generation. Based on the linear dose-response, Y = a + b D, where Y is the yield of aberrant cells, a the spontaneous frequency and b the linear regression coefficient, the doubling dose is calculated as the ratio of a to b (DD = a/b).

Results and discussion

Test resultsopen allclose all
Sex:
male
Genotoxicity:
positive
Remarks:
Chromosomal aberration test; mouse (bone marrow)
Toxicity:
not specified
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
not applicable
Sex:
male
Genotoxicity:
positive
Remarks:
Germ cell chromosome aberration test; mouse (spermatogonia)
Toxicity:
not specified
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
not valid

Any other information on results incl. tables

Bone Marrow:

Benzene showed high clastogenic activity in bone marrow cells at all sampling times with a peak at 24 and 30 hours (approx. 20% aberrant cells (excl. gaps) versus 1% in controls). The dose-response was determined 24 h after treatment with 0.1, 0.5 or 1.0 mL/kg benzene (equivalent to 88, 440 and 880 mg/kg bw). All three doses were clearly positive and a dose-dependency was established.

 

Chromatid aberrations in bone marrow cells of mice treated with 1 mL/kg (880 mg/kg) of benzene: time-response

Time (h)

No. cells scored a

No. of aberrations

Highly damaged cells (n) b

Aberrant cells (%±SE)

 

 

gaps

breaks

exchanges

 

 including gaps

excluding gaps 

Control

1000

24

11

-

-

3.2 ± 0.6

1.1 ± 0.1

6

600

47

29

-

-

11.3 ± 0.1

4.3 ± 0.6**

12

600

89

98

7

-

24.6 ± 2.4

16.6 ± 0.4**

18

600

59

112

7

3

22.6 ± 4.5

15.3 ± 3.0**

24

600

53

206

6

13

25.1 ± 2.7

20.8 ± 3.3**

30

600

117

237

15

13

28.7 ± 7.4

19.8 ± 0.5**

36

600

10

24

-

-

4.8 ± 0.4

3.5 ± 0.5**

42

600

26

31

-

-

8.6 ± 1.4

5.3 ± 0.4**

48

600

41

44

-

-

12.0 ±1.7

6.3 ± 1.1**

**P <0.01 (Fisher's exact test).

a  200 cells scored per animal.

b  Cells with more than 10 aberrations.

 

Spermatogonia:

After administration of 1 mL/kg (880 mg/kg bw) the maximum response was obtained 24 h after treatment (6.3% aberrant cells versus 1.2% in negative controls). In the dose-response study, all doses tested (0.25, 0.5 and 1.0 mL/kg bw, equivalent to 220, 440 and 880 mg/kg bw) increased the aberration frequency in a dose-dependent manner; at 880 mg/kg again 6.3% of the spermatogonia were aberrant. Since bone marrow clastogenicity was investigated in parallel, it can be concluded that clastogenicity in bone marrow cells and spermatogonia was induced in the same dose range, although effects were less pronounced in spermatogonia.

 

Chromatid aberrations in differentiating spermatogonia of mice treated with 1 mL/kg (880 mg/kg) of benzene: time-response

Time (h)

No. cells scored a

No. of aberrations

Aberrant cells (%±SE)

 

 

gaps

breaks

exchanges

 including gaps

 excluding gaps

Control

1000

49

12

-

5.5 ± 0.9

1.12 ± 0.2

6

600

32

6

-

6.3 ± 0.1

1.0 ± 0.3

12

600

63

18

1

12.3 ± 0.3

3.3 ± 0.4**

18

600

67

24

-

13.3 ± 1.2

4.0 ± 0.5**

24

600

54

36

3

14.8 ± 2.6

6.3 ± 1.6**

30

600

33

16

1

7.8 ± 1.6

2.6 ± 0.5*

36

600

31

23

1

8.3 ± 1.0

3.5 ± 0.5**

42

600

21

14

-

5.2 ± 1.3

2.0 ± 0.5

48

600

19

23

-

18.2 ±2.0

3.5 ± 0.7**

**P <0.01 (Fisher's exact test).

a  200 cells scored per animal.

 

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): positive Chromosomal aberration test (mouse bone marrow) and Germ cell chromosome aberration test (mouse spermatogonia)
Benzene was positive in the chromosomal aberration test (mouse bone marrow) and germ cell chromosome aberration test (mouse spermatogonia), following a single oral dose of 1 mL/kg to male mice.
Executive summary:

The ability of benzene to induce chromosome damage in vivo was assessed by determining the frequencies of chromosomal aberrations in bone marrow and spermatogonial cells of male Swiss CDI mice. Initially a single dose of 1 mL benzene/kg (880 mg/kg) was assessed using a wide range of times (6, 12, 18, 24, 30, 36, 42 and 48 hours) to determine the time of maximum response. Benzene showed high clastogenic activity with a peak between 24 and 30 hours in bone marrow cells or 24 hours in differentiating spermatogonia. The effect in bone marrow cells was greater than in spermatogonia. Secondly, the dose response 24 hours after treatment was determined. Additional doses of benzene used were: 0.1 mL/kg (88 mg/kg) and 0.5 mL/kg (440 mg/kg) for bone marrow cells; 0.25 mL/kg (220 mg/kg) and 0.5 mL/kg (440 mg/kg) for differentiating spermatogonia.

Benzene was positive in this test with dose dependent clastogenic effects in both cell types. All dose levels showing a statistically significant increase in the incidence of aberrant cells.

It is concluded that benzene is a clastogen in male germ cells and the bone marrow of mice.