Registration Dossier

Toxicological information

Genetic toxicity: in vivo

Currently viewing:

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
yes (incl. certificate)
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Physical state: liquid
- Analytical purity: 97.4%
- Purity test date: 18 July 2002, analytical report
- Lot/batch No.: B 02011
- Stability under test conditions: the stability of the test substance under storage conditions is guaranteed as indicated by the sponsor.
- Storage condition of test material: room temperature, protected from light and moisture

Test animals

Species:
mouse
Strain:
NMRI
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Deutschland GmbH
- Age at study initiation: 5-8 weeks
- Weight at study initiation: about 29 g
- Assigned to test groups randomly: yes, under following basis: randomized plan prepared with an appropriate computer program
- Housing: Makrolon cages, type MI, housed individually from start of the treatment until the end of the test
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24 °C
- Humidity (%): 30-70%
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Vehicle/solvent used: DMSO
- Justification for choice of solvent/vehicle: Due to the hydrolytical sensitivity of the test substance in water, DMSO was selected as the vehicle, which
had been demonstrated to be suitable in the in vivo micronucleus test and for which historical data are available.
- Concentration of test material in vehicle: 12.5 g/100 ml, 25.0 g/100 ml and 50.0 g/100 ml.
- Amount of vehicle: 4 ml/kg bw.
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
All test substance formulations were prepared immediately before administration.
The amount of substance or volume to be administered was related to the specific weight of the individual animals on the day of the experiment.
Duration of treatment / exposure:
single dose
Frequency of treatment:
once, single dose
Post exposure period:
24 or 48 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
500, 1000, 2000 mg/kg bw
Basis:
nominal conc.
No. of animals per sex per dose:
5 animals per dose for the 24 hour sacrifices and 5 animals per dose for the 48 hour sacrifices
Control animals:
yes, concurrent vehicle
Positive control(s):
cyclophosphamide (CPP) and vincristine sulphate (VCR)
- Justification for choice of positive controls: The stability of CPP and VCR is well-defined under the selected conditions, since both positive control
articles are well-defined clastogens and aneugens respectively.
- Route of administration: The positive controls, both, dissolved in purified water were administered to male animals once orally or intraperitoneally
each in a volume of 10 ml/kg body weight.
- Doses / concentrations: 20 mg CPP//kg body weight for clastogenic effects and 0.15 mg VCR/kg body weight for aneugenic effects.

Examinations

Tissues and cell types examined:
In general, 2000 polychromatic erythrocytes (PCEs) from each of the animals of every test group are evaluated and investigated for micronuclei (MN).
The normochromatic erythrocytes (NCEs) which occur are also scored .
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION:
In a pretest for the determination of the acute oral toxicity, 2000 mg/kg body weight recommended as the highest dose according to the OECD
Guideline were survived by all animals (male and female) without any clinical signs. Thus, only male animals were used for the cytogenetic
investigations. Therefore, a dose of 2000 mg/kg body weight was selected as the highest dose in the present cytogenetic study. 1000 mg/kg and 500 mg/kg body weight were administered as further doses.

TREATMENT AND SAMPLING TIMES:
The animals were sacrificed and the bone marrow of the two femora was prepared 24 and 48 hours after administration in the híghest dose group of
2000 mg/kg body weight and in the vehicle controls. In the test groups of 1000 mg/kg and 500 mg/kg body weight and in the positive control groups,the 24-hour sacrifice interval was investigated only.

DETAILS OF SLIDE PREPARATION:
The two femora were prepared by dissection and removing all soft tissues. After cutting off the epiphyses, the bone marrow was flushed out of the
diaphysis into a centrifuge tube using a cannula filled with fetal calf serum which was at 37°C (about 2 ml/femur). The suspension was mixed
thoroughly with a pipette, centrifuged at 300 x g for 5 minutes, the supernatant was removed and the precipitate was resuspended in about 50 µl fresh FCS. One drop of this suspension was dropped onto clean microscopic slides, using a Pasteur pipette. Smears were prepared using slides with ground edges, the preparations were dried in the air and subsequently stained.
The slides were stained in eosin and methylene blue solution for 5 minutes (May Grünwald solution modified = Wrights solution), rinsed in purified
water and then placed in fresh purified water for 2 or 3 minutes. They were finally stained in 7.5% Giemsa solution for 15 minutes.
After being rinsed twice in purified water and clarified in xylene, the preparations were mounted using Corbit-Balsam.

METHOD OF ANALYSIS:
In general, 2,000 polychromatic erythrocytes (PCEs) from each of the animals of every test group are evaluated and investigated for micronuclei (MN).
The normochromatic erythrocytes (NCEs) which occur are also scored. The following parameters are recorded:
- Number of polychromatic erythrocytes
- Number of polychromatic erythrocytes containing micronuclei
The increase in the number of micronuclei in polychromatic erythrocytes of treated animals as compared with the solvent control group provides an
index of a chromosome-breaking (clastogenic) effect or of a spindle activity of the substance tested.
- Number of normochromatic erythrocytes
- Number of normochromatic erythrocytes containing micronuclei
The number of micronuclei in normochromatic erythrocytes at the early sacrifice intervals shows the situation before test substance administration andmay serve as a control value. A substance-induced increase in the number of micronuclei in normocytes may be found with an increase in the duration of the sacrifice intervals.
- Ratio of polychromatic to normochromatic erythrocytes
An alteration of this ratio indicates that the test substance actually reached the target. Individual animals with pathological bone marrow depression
may be identified and excluded from the evaluation.
- Number of small micronuclei (dD/4) (d = diameter of micronucleus, D= cell diameter)
The size of micronuclei may indicate the possible mode of action of the test substance, i .e . a clastogenic or a spindle poison effect.
Slides were coded before microscopic analysis.
Since the absolute values shown have been rounded off but the calculations were made using the unedited values, deviations in the given relative
values can occur.

Evaluation criteria:
The mouse micronucleus test is considered valid if the following criteria are met:
- The quality of the slides allowed the identification and evaluation of a sufficient number of analyzable cells, i .e. >=2000 polychromatic erythrocytes.
- The proportion of cells with micronuclei in negative control animals was within the normal range of the historical control data.
- The two positive control chemicals induced a significant increase in the number of cells containing small and large micronuclei within the range of
the historical control data or above.

The test chemical is considered positive in this assay if the following criteria are met:
- A dose-related and significant increase in the number of micronucleated polychromatic erythrocytes at any of the intervals.
- The proportion of cells containing micronuclei exceeded both the values of the concurrent negative control range and the negative historical control range.
A test substance is generally considered negative in this test system if:
- There was no significant increase in the number of micronucleated polychromatic erythrocytes at any dose above concurrent control frequencies and at any time.
- The frequencies of cells containing micronuclei were within the historical control range.
Statistics:
The statistical evaluation of the data was carried out using the program system MUKERN.
The number of micronuclei in polychromatic erythrocytes was analyzed.
A comparison of the dose group with the vehicle control was carried out using the Wilcoxon test for the hypothesis of equal medians . Here, the relative frequencies of cells with micronuclei of each animal were used. If the results of this test were significant, labels (* for p <=0.05, ** for p<=0.01) were printed with the group means in the tables. This test was performed one-sided.

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Toxicity:
not specified
Vehicle controls valid:
yes
Negative controls valid:
yes
Positive controls valid:
yes

Any other information on results incl. tables

Single oral administration of the test substance did not result in any increase 
in the number of polychromaticerythrocytes containing either small or large 
micronuclei. The rate of micronuclei was always close to the range as
that of the concurrent negative control and within the range of historical control data. No inhibition of erythropoesis determined from the ratio of polychromatic to normochromatic erythrocytes was detected. According to the authors, the test substance did not have any chromosome-damaging (clastogenic) effect, and there was no indication of any impairment of chromosome distribution in the course of mitosis (aneugenic activity) in bone marrow cells in vivo.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
Under the experimental conditions chosen here, the test substance has no chromosome-damaging (clastogenic) effect nor does it lead to any impairment of chromosome distribution in the course of mitosis (aneugenic activity) in bone marrow cells in vivo.
Executive summary:

The substance was tested for chromosomal damage (clastogenicíty) and for the ability to induce spindle poison effects (aneugenic activity) in NMRI mice using the micronucleus test method according to OECD guideline 474. For this purpose, the test substance, dissolved in DMSO, was administered once orally to male animals at dose levels of 500 mg/kg, 1,000 mg/kg and 2,000 m g/kg body weight in a volume of 4 ml/kg body weight in each case. As a negative control, male mice were administered merely the vehicle, DMSO, by the same route, which gave frequencies of micronucleated polychromatic erythrocytes within the historical control range. Both of the positive control chemicals, i .e . cyclophosphamide for clastogenicity and vincristine for spindle poison effects, led to the expected increase in the rate of polychromatic erythrocytes containing small or large micronuclei .

Animals which were administered the vehicle or the positive control substances cyclophosphamide or vincristine did not show any clinical signs of toxicity. The administration of the test substance was tolerated by all animals without any signs or symptoms .

The animals were sacrificed and the bone marrow of the two femora was prepared 24 and 48 hours after administration in the híghest dose group of 2,000 mg/kg body weight and in the vehicle controls . In the test groups of 1,000 mg/kg and 500 mg/kg body weight

and in the positive control groups, the 24-hour sacrifice interval was investigated only . After staining of the preparations, 2,000 polychromátic erythrocytes were evaluated per animal and investigated for micronuclei . The normocytes with and without micronuclei

occurring per 2,000 polychromatic erythrocytes were also recorded. According to the results of the present study, the single oral administration of the test substance did not lead to any increase in the number of polychromatic erythrocytes containing either small or large micronuclei . The rate of micronuclei was always close to the range as that of the concurrent negative control in all dose groups

and at all sacrifice intervals and within the range of the historical control data. No inhibition of erythropoiesis determined from the ratio of polychromatic to normochromatic erythrocytes was detected .