Tetrachloro-p-benzoquinone

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well performed OECD and GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1990

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

of 1983

Deviations:

no

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Tetrachloro-p-benzoquinone

EC Number:

204-274-4

EC Name:

Tetrachloro-p-benzoquinone

Cas Number:

118-75-2

Molecular formula:

C6Cl4O2

IUPAC Name:

2,3,5,6-tetrachloro-1,4-benzoquinone

Details on test material:

- Name of test material (as cited in study report): Chloranil

Test animals

Species:

mouse

Strain:

other: OF1; IOPS Caw

Sex:

male/female

Details on test animals or test system and environmental conditions:

Mice, 6 to 8 weeks old, with appropriate range of bodyweight at study start were used. Immediately prior to dosing, live bodyweight range males: 27.5 - 37.6 g, females: 21.9 - 27.5 g. Animal housing and environmental conditions were appropriate for in vivo mutagenicity testing in mice, although the acclimatisation period of at least 24 hours was shorter than requested in current technical test guidelines. Commercially available rat mouse diet and filtered and softened drinking tap-water were fed ad libitum. Quality of drinking water and nutrition was regularly monitored by bacterial and/or chemical analysis.

Administration / exposure

Route of administration:

other: Substance and vehicle control groups: by oral gavage. Positive control group: intraperitoneal.

Vehicle:

vehicle for control and test substance treated groups: 10% (w/v) gum arabic dispersed in distilled water.
vehicle for positive control group (cyclophosphamide): water (for injection)

Duration of treatment / exposure:

Single dose followed by 24 to 72 hours of observation.

Frequency of treatment:

single dose

Post exposure period:

Vehicle control group: 24 or 48 or 72 hours
Test substance treated group: 24 or 48 or 72 hours
Positive control group: 24 hours

Doses / concentrations

Remarks:

Doses / Concentrations:
2500 mg/kg bodyweight
Basis:
actual ingested
oral gavage, administration volume = 10 ml/kg bw

No. of animals per sex per dose:

15 males and 15 females: 5 males and 5 females each killed 24 hours, 48 hours and 72 hours post administration.

Control animals:

yes, concurrent vehicle

Positive control(s):

Cyclophosphamide at 100 mg/kg bw intraperitoneally administered as a 1% (w/v) aqueous solution. 5 males and 5 females each killed 24 hours post administration.

Examinations

Tissues and cell types examined:

Bone marrow cells from both femurs/animal. Two slides were prepared from each animal and 1000 erythrocytes/animal (500 cells/slide) evaluated using a microscope. Numbers of micronucleus-containing polychromatic erythrocytes and the ratio of polychromatic to normochromatic erythrocytes were determined.

Details of tissue and slide preparation:

Bone marrow was extracted from both femurs using a syringe and suspended in fetal calf serum. The suspension was centrifuged and the cell pellet was re-suspended prior to being spread on the slide. The slides were stained with May-Grünwald-Giemsa.

Evaluation criteria:

An increase in the frequency of micronucleus-containing polychromatic erythrocytes in treated animals compared with negative controls is an indication of induced chromosome damage.

Statistics:

Student t-test.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

Premature death of 2 vehicle control females + 1 treated female; no clinical signs except a poor health condition in one of the decedent control females, indication of slight, transient cytotoxicity in the test substance treated group.

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Any other information on results incl. tables

Two females of the vehicle control group died probably due to an intubation error. In addition one female of the test substance treated group was found dead 48 hours post administration. Clinical signs were not evident in animals of the treated group. For one of the decedent vehicle control animals poor health (weakness) was recorded 48 hours post administration.

 

At 24, 48 and 72 hours post administration, toxicologically relevant differences between the numbers of micronucleus-containing polychromatic erythrocytes in the vehicle control group and in the test substance treated group were not evident. The counts of micronucleus-containing polychromatic erythrocytes were significantly higher and the ratios of polychromatic to normochromatic erythrocytes were lower in the positive control group than in the other groups demonstrating the validity of the test. A slight trend to the ratio of polychromatic to normochromatic erythrocytes being lower in test substance treated animals than in vehicle controls at 24 and 48 hours post administration had returned to a mean value similar to that in the vehicle control group by 72 hours post administration and was interpreted as an indication of slight, transient toxicity of the test substance impairing erythropoiesis.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative No indication of mutagenicity
In the present in vivo mammalian erythrocyte micronucleus test (OECD 474), a single dose of 2500 mg/kg bw of the test substance, 2,3,5,6-tetrachloro-1,4-benzoquinone, to mice did not induce numbers of micronucleus-containing polychromatic erythrocytes from bone marrow statistically significantly higher than concurrent vehicle controls over periods of 24, 48 or 72 hours. Therefore, there was no indication of mutagenicity of the test substance in the present study. The validity of the test was evident from counts of micronucleus-containing polychromatic erythrocytes being significantly higher and from the ratio of polychromatic to normochromatic erythrocytes being lower in the positive control group (treated with cyclophosphamide) than in the other groups. A slight trend to the ratio of polychromatic to normochromatic erythrocytes being lower in test substance treated animals than in vehicle controls at 24 and 48 hours post administration and being similar to vehicle controls at 72 hours post administration, was interpreted as an indication of slight, transient toxicity of the test substance impairing erythropoiesis.

Executive summary:

2,3,5,6-tetrachloro-1,4-benzoquinone was tested for mutagenicity in an in vivo mammalian erythrocyte micronucleus test according to OECD Guideline 474. Reliability grade 1 was assigned to the study. A group of 15 male and 15 female mice was treated by single oral gavage administration with 2,3,5,6-tetrachloro-1,4-benzoquinone at a dose of 2500 mg/kg bw. For administration, the test substance was suspended in an aqueous 10% (w/v) gum arabic dispersion. The animals, 5 males and 5 females each, were killed at 24, 48 and 72 hours after dosing. In addition, vehicle controls (mice receiving the vehicle alone) and positive controls (dosed intraperitoneally with cyclophosphamide at 100 mg/kg bw) were included in the study. Bone marrow cells were collected for erythrocyte micronucleus analysis from vehicle control and test animals at 24, 48 and 72 hours post administration and from positive control animals at 24 hours post administration. For each animal, cells were taken from both femurs preparing two slides/animal and evaluating by use of a microscope 500 cells/ slide (1000 cells/animal) for the presence of micronuclei. Numbers of micronucleus-containing polychromatic erythrocytes and the ratio of polychromatic to normochromatic erythrocytes were determined for each animal.

Two females of the vehicle control group died probably due to an intubation error. In addition one female of the test substance treated group was found dead 48 hours post administration, but clinical signs were not evident in this group. At 24, 48 and 72 hours post administration, toxicologically relevant differences between the numbers of micronucleus-containing polychromatic erythrocytes in the vehicle control group and in the test substance treated group were not evident. Therefore, there was no indication of mutagenicity of the test substance in the present study. The counts of micronucleus-containing polychromatic erythrocytes were significantly higher and the ratios of polychromatic to normochromatic erythrocytes were lower in the positive control group than in the other groups demonstrating the validity of the test. A slight trend to the ratio of polychromatic to normochromatic erythrocytes being lower in test substance treated animals than in vehicle controls at 24 and 48 hours post administration had returned to a mean value similar to that in the vehicle control group by 72 hours post administration and was interpreted as an indication of slight, transient toxicity of the test substance impairing erythropoiesis.