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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study but no data on test substance purity

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report Date:
1990

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Deviations:
yes
Remarks:
no data on substance purity
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: Hoechst AG: Kastengrund, SPF breeding colony
- Age at study initiation: no data
- Weight at study initiation: males 32-42 g; females 24-36 g
- Assigned to test groups randomly: yes
- Fasting period before study: no data
- Housing: no data
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2 deg C
- Humidity (%): 55 +/- 10%
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: no data

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
Sesame oil
Duration of treatment / exposure:
Single gavage dose
Frequency of treatment:
once
Post exposure period:
24, 48 or 72 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
1800 mg/kg
Basis:
actual ingested
No. of animals per sex per dose:
5
Control animals:
yes, concurrent vehicle
Positive control(s):
Cyclophosphamide (Endoxan(R)), 50 mg/kg

Examinations

Tissues and cell types examined:
Bone marrow

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
valid
Positive controls validity:
valid
Additional information on results:
RESULTS OF RANGE-FINDING STUDY
- Dose range: 2000-5000 mg/kg
- Solubility: soluble in sesame oil
- Clinical signs of toxicity in test animals: ataxic gait, abnormal/reduced movement, tonic/clonic convulsions, coma, death
- Evidence of cytotoxicity in tissue analyzed: not reported
- Rationale for exposure: standard test route

RESULTS OF DEFINITIVE STUDY
- Induction of micronuclei (for Micronucleus assay): no increase
- Ratio of PCE/NCE (for Micronucleus assay): not affected
- Appropriateness of dose levels and route: maximum tolerated dose
- Statistical evaluation: by "Diamant" computer program v2

Any other information on results incl. tables

In the preliminary toxicity study, mortalities were:

5000 mg/kg: male 1/3; female 3/3. 3000 mg/kg: male 0/3; female 1/3. 2000 mg/kg: male 0/3; female 0/6

Significant clinical signs were reported at all dose levels. Clinical signs at 2000 mg/kg included ataxic/uncoordinated gait, forward movement in crawling posture, tonic/clonic convulsions, trembling, piloerection. The dose level determined for the main study was 1800 mg/kg.

In the main study at 1800 mg/kg, 2/30 females died. They were replaced and replacements survived after treatment.

Signs of toxicity noted were ataxic gait, reduced spontaneous activity, abdominal position, forward movement in crawling posture, piloerection, narrowed palpebral fissures, saltatory and rolling convulsions, tonic convulsions, impaired general condition.All clinical signs had resolved after 48 hours. There were no abnormal macroscopic findings on necropsy.

There was no statistically significant increase in micronucleated polychromatic erythrocytes. The number of normochromatic erythrocytes with micronuclei did not differ from the values in negative control animals at any of the three killing times investigated. The ratio of polychromatic to normochromatic erythrocytes was essentially unaffected by treatment.

Cyclophosphamide (Endoxan(R) at 50 mg/kg induced a marked and statistically sigificant increase in the number of polychromatic erythrocytes with micronuclei in both males and females..

Applicant's summary and conclusion

Conclusions:
Interpretation of results: negative
TBEP was not mutagenic in this test system.
Executive summary:

TBEP was tested in the micronucleus test. Following a preliminary toxicity study at dose levels of 2000 -5000 mg/kg bw, the test compound was administered once by gavage to male and female NMRI mice, at doses of 0 and 1800 mg/kg in sesame oil. The animals were observed and killed 24, 48 or 72 hours after test compound administration. endoxan(R) (cyclophosphamide) was used as a positive control at 50 mg/kg.

2/30 females died. They were replaced and replacements survived after treatment.

Signs of toxicity noted were ataxic gait, reduced spontaneous activity, abdominal position, forward movement in crawling posture, piloerection, narrowed palpebral fissures, saltatory and rolling convulsions, tonic convulsions, impaired general condition.All clinical signs had resolved after 48 hours. There were no abnormal macroscopic findings on necropsy.

There was no statistically significant increase in micronucleated polychromatic erythrocytes. The number of normochromatic erythrocytes with micronuclei did not differ from the values in negative control animals at any of the three killing times investigated. The ratio of polychromatic to normochromatic erythrocytes was essentially unaffected by treatment.

Cyclophosphamide (Endoxan(R) induced a marked and statistically sigificant increase in the number of polychromatic erythrocytes with micronuclei in both males and females.

TBEP was therefore considered not to be mutagenic in this test system.