Registration Dossier

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:
key study
Study period:
From 14 nov 1995 to 15 feb 1996
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996
Report Date:
1996

Materials and methods

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

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Hydrochinondimethylether

Test animals

Species:
mouse
Strain:
NMRI
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Tierzucht Scönwalde GmbH i.G., Hauptstrasse 62, 16352 Schönwalde
- Age at study initiation: 7 weeks
- Weight at study initiation: males: mean 34.4 g; females: mean 28.1 g
- Assigned to test groups randomly: yes, under following basis: randomisation schemes 95.0790 and 95.0791
- Fasting period before study: no data
- Housing: in makrolon cages Type 3, five animals per cage on soft wood granulate
- Diet: rat/mice diet ssniff R/M-H (V 1534), ad libitum. ssniff GmbH, Postbox 2039, 59480 Soest.
- Water: tap water in plastic bottles ad libitum
- Acclimation period: 1 week under study conditions


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3°C
- Humidity (%): 50 +/- 20%
- Air changes (per hr): in fully air-conditioned room.
- Photoperiod (hrs dark / hrs light): 12h / 12h daily

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Vehicle(s)/solvent(s) used: starch mucilage at the appropriate concentration.
Details on exposure:
no data
Duration of treatment / exposure:
Once orally.
Frequency of treatment:
1 exposure
Post exposure period:
None
Doses / concentrations
Remarks:
Doses / Concentrations:
0; 2000 mg/kg bw
Basis:
nominal conc.
No. of animals per sex per dose:
5 males and 5 females per dose.
Control animals:
yes, concurrent vehicle
Positive control(s):
Endoxan R containing cyclophosphamide, soluted in distilled water.
- Route of administration: oral, gavage
- Doses / concentrations: 50 mg/kg bw

Examinations

Tissues and cell types examined:
Bone marrow smears for the occurence of micronuclei in red blood cells were examined.
Cell types examined: polychromatic and normochromatic erythrocytes.
Details of tissue and slide preparation:
The animals were killed by carbon dioxide asphyxiation 12, 24 or 48 hours after administration. For each animal, about 3 ml foetal bovine serum was poured into a centrifuge tube. Both femora were removed and the bones freeds of muscle tissue. The proximal ends of the femora were opened and the bone marrow flushed into the centrifuge tube. A suspension was formed. The mixture was then centrifuged for 5 minutes at approximlately 1200 rpm, after which almost all the supernantant was discarded. One drop of the thoroughly mixed sediment was smeared onto a clean slide, identified by project code and animal number and air-dried for about 12 hours.
Evaluation criteria:
1000 polychromatic erythrocytes were counted for each animal. The number of cells with micronuclei was recorded, not the number of individual micronuclei. As a control measure 1000 mature erythrocytes were also counted and examined for micronuclei.
In addition, the ratio of polychromatic to normochromatic erythrocytes was determined. All bone marrow smears for evaluation were coded to ensure that the group from which they were taken remained unknown to the investigator. The number of polychromatic erythrocytes with micronuclei occuring in the 1000 polychromatic erythrocytes, and the number of normocytes with micronuclei occuring in the 1000 normocytes were evaluated statistically.
Statistics:
Wilcoxon-Test.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
valid
Additional information on results:
RESULTS OF RANGE-FINDING STUDY
- Dose range: 2000 mg/kg bw
- number of animals: 3 males and 3 females.
- Clinical signs of toxicity in test animals: none
- mortality: none
- Macroscopic finding: no macroscopic findings were observed

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
Paradimethoxybenzene is not mutagenic in the micronucleus test in male and female NMRI mice.
Executive summary:

The micronucleus test was performed with Paradimathoxybenzene (Hoechst, 1996), according to the OECD 474 guideline under GLP conditions.

The test compound was suspended in starch mucilage and was given once as an orally dose of 2000 mg/kg bw to male and female NMRI mice, based on the results of a preliminary study.

According to the test procedure, the animals were killed 12, 24 or 48 hours after administration.

Endoxan (cyclophosphamide in distilled water) was used as positive control substance and was administered once orally at a dose of 50 mg/kg bw.

The number of polychromatic and normochromatic erythrocytes containing micronuclei was not increased. The ration of polychromatic/normochromatic erythrocytes in both male and female animals remained unaffected by the treatment with Paradimethoxybenzene and was statistically not different from the control values.

Positive control induced in both males and females a marked statistically significant increase in the number of polychromatic cells with micronuclei, indicating the sensitivity of the test system. The ratio of polychromatic erythrocytes to normocytes was not changed to a significant extent.

Under the test conditions, the results indicate that Paradimethoxybenzene is not mutagenic in the micronucleus test.