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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-07-29 to 2010-09-29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report date:
2010

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Version / remarks:
as at 1997
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)
Version / remarks:
as at 2008
GLP compliance:
yes (incl. QA statement)
Remarks:
German GLP
Type of assay:
mammalian erythrocyte micronucleus test

Test material

Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material: TZ5978 / BOP 07-09
- Expiration date of the lot/batch: July 31, 2014
-
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature

Test animals

Species:
mouse
Strain:
NMRI
Details on species / strain selection:
The mouse is an animal that has been used for many years as a suitable experimental animal in cytogenetic investigations. There are many data available from such investigations, which may be helpful in the interpretation of results from the micronucleus test. In addition, the mouse is an experimental animal in many physiological, pharmacological and toxicological studies. Data from such experiments also may be useful for the design and the performance of the micronucleus test
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Harlan Laboratories B.V., Postbus 6174, 5960 AD Horst / The Netherlands
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: males mean value = 36.7 g (SD ± 1.5 g)
- Fasting period before study: no
- Housing: singly in Makrolon Type II/III cages with wire mesh top (EHRET GmbH, 79302 Emmendingen, Germany) and granulated soft wood bedding (Rettenmaier & Söhne GmbH + Co. KG,73494 Rosenberg, Germany)
- Diet: pelleted standard diet, ad libitum(Harlan Laboratories B.V. Postbus 6174, 5960 AD Horst, The Netherlands)
- Water: tap water, ad libitum
- Acclimation period: >= 5 d

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 45 - 100
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Vehicle(s)/solvent(s) used: water
- Source: B. Braun Melsungen AG 34212 Melsungen, Germany
- Catalogue no.: 6724092.00.00
- Justification for choice of solvent/vehicle: chosen for its relative non-toxicity for animals
- Concentration of test material in vehicle: 50, 100, 200 mg/mL
- Amount of vehicle (if gavage or dermal): 10 mL/kg
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
The test item was formulated in in the vehicle (sterile water).
Duration of treatment / exposure:
single oral gavage on Day 1
Frequency of treatment:
single oral gavage
Post exposure period:
no
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (nominal)
Remarks:
Control
Dose / conc.:
500 mg/kg bw/day (nominal)
Remarks:
Low dose
Dose / conc.:
1 000 mg/kg bw/day (nominal)
Remarks:
Middle dose
Dose / conc.:
2 000 mg/kg bw/day (nominal)
Remarks:
High dose
Dose / conc.:
2 000 mg/kg bw/day (nominal)
Remarks:
Positive Control
No. of animals per sex per dose:
- main test: 7 males per dose (only males were used in the main study as the toxicity pretest showed comparable susceptibility of males and females)
- toxicity pre-test: 2 males and 2 females per dose
Control animals:
yes, concurrent vehicle
Positive control(s):
none; no data; cyclophosphamide (CPA)
- Supplier: Fisher Scientific GmbH, 61130 Nidderau, Germany
- Justification for choice of positive control(s): recommended as positive control substance in the OECD guideline
- Route of administration: oral gavage
- Doses / concentrations: 40 mg/Kg bw (concentration in vehicle (water): 4 mg/mL)

Examinations

Tissues and cell types examined:
bone marrow cells
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION:
2000 mg/kg bw is the limit dose according to the OECD guideline. Two lower doses with a spacing factor of 2 were selected.

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):
- single aoral treatment
- Sampling:
- pre-test: examination for acute toxic symptoms 1 h, 2-4 h, 6 h, 24 h, 30 h, and 48 h after administration
- main test: examination for acute toxic symptoms 1 h, 2-4 h, 6 h, 24 h (and 48 h) after administration; animals of all dose levels sacrificed at 24 h post dosing, an additional high dose group sacrificed 48 post treatment

DETAILS OF SLIDE PREPARATION:
- sacrifices of animals using CO2 followed by bleeding
- removal of the femora, cutting off of epiphyses, marrow flushed out with foetal calf serum using a syringe
- centrifugation of the cell suspension at 1500 rpm (390 x g) for 10 minutes
- discarding of supernatant, resuspesion of the remaining cell pellet and spreading of a small drop of the suspension on a slide
- air drying of the slide and staining with May-Grünwald (Merck, 64293 Darmstadt, Germany)/Giemsa (Merck, 64293 Darmstadt, Germany)
- mounting of cover slips with EUKITT (Kindler, 79110 Freiburg, Germany)
- preparation of at least one slide per each bone marrow sample

METHOD OF ANALYSIS:
- slide analysis using NIKON microscopes with 100x oil immersion objectives
- analysis for micronuclei of 2000 polychromatic erythrocytes (PCE) per animal
- determination of ratio between polychromatic and normochromatic erythrocytes in the same sample for detection of cytotoxicity
- cytotoxicity expressed in polychromatic erythrocytes per 2000 erythrocytes
- slides were coded
- use of samples from all animals per test group

OTHER:
Evaluation criteria:
The study was considered valid as the following criteria are met:
- at least 5 animals per group can be evaluated.
- PCE to erythrocyte ratio should not be less than 20 % of the negative control.
- the positive control shows a statistically significant and biological relevant increase of
micronucleated PCEs compared to the negative control.

Positive result:
If the test item induces either a dose-related increase or a clear increase in the number of micronucleated polychromatic erythrocytes in a single dose group. Statistical methods (nonparametric Mann-Whitney test) will be used as an aid in evaluating the results. However, the primary point of consideration is the biological relevance of the results.

Negative result
If the test item that fails to produce a biological relevant increase in the number of micronucleated polychromatic erythrocytes it is considered non-mutagenic in this system.

Results and discussion

Test results
Key result
Sex:
male
Genotoxicity:
negative
Toxicity:
no effects
Remarks:
The animals treated with 2000 mg/kg b.w. did not express any toxic reactions. However, discoloured urine was observed (orange) in animals treated with 2000 mg/kg bw both in pre-test and main experiment.
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
- Solubility: no problems with solubility reported
- Clinical signs of toxicity in test animals:
- no adverse effects
- orange discoloration of the urine, indicating bioavailability of the test item which is a red dye
- Evidence of cytotoxicity in tissue analyzed: no
- Rationale for exposure: 2000 mg/kg bw is the limit dose recommended in the OECD guideline.


RESULTS OF DEFINITIVE STUDY
- Types of structural aberrations for significant dose levels (for Cytogenetic or SCE assay): not applicable
- Induction of micronuclei (for Micronucleus assay):
- No micronuclei induced in any of the treatment groups
- Micronuclei induced in the positive control group at the expected rate, indicating the sensitivity of the test system
- for details see Tables 2 and 3
- Ratio of PCE/NCE (for Micronucleus assay):
- not significantly changed in any of the treatment groups
- for details see Tables 2 and 3
- Appropriateness of dose levels and route:
- orange discoloration of the urine in the highest dose group, indicating bioavailability of the test item which is a red dye
- testing up to the limit dose
- Statistical evaluation: non-parametric Mann-Whitney test

Any other information on results incl. tables

Table 2: Summary of Micronucleus Test Results

Test group

Dose mg/kg b.w.

Sampling time (h)

PCEs with micronuclei (%)

range

PCE per 2000 erythocytes

Vehicle

0

24

0.079

0 - 5

1219

Test item

500

24

0.186

0 - 8

1264

Test item

1000

24

0.107

1 - 6

1177

Test item

2000

24

0.136

2 - 6

1203

Positive control

40

24

2.979

23 -82

1118

Test item

2000

48

0.057

0 - 2

1233

Table 3: Statistical significance at the five per cent level (p < 0.05, evaluated by means of the non-parametric Mann-Whitney test).

Vehicle control versus test group

Significance

p

500 mg test material/kg b.w.; 24 h

-

0.0758

1000 mg test material/kg b.w.; 24 h

-

0.2287

2000 mg test material/kg b.w.; 24 h

-

0.0807

40 mg CPA/kg b.w.; 24 h

+

0.0003

2000 mg test material/kg b.w.; 48 h

-

n.t.

-         =         not significant

+         =         significant

n.t. = not tested

Table 4: Historical controls from 2003 - 2009

 

Negative Controls Males

Positive Controls (CPA) Males

Mean* ± SD

0.096 ± 0.040

2.332 ± 0.696

Range**

0.01 - 0.22

0.70 - 4.52

No. of Experiments

318

316

*:        mean value (percent micronucleated cells)

**:      range of the mean group values (percent micronucleated cells)

Applicant's summary and conclusion

Conclusions:
FAT 40850/A did not induce micronuclei as determined by the in-vivo micronucleus test in the bone marrow cells of the mouse.
Executive summary:

FAT 40850/A was assessed in the in-vivo micronucleus assay for its potential to induce micronuclei in polychromatic erythrocytes (PCE) in the bone marrow of the mouse according to OECD TG 474. The test item was formulated in sterile water, which was also used as vehicle control. The volume administered orally was 10 mL/kg b.w. 24 h and 48 h after a single administration of the test item the bone marrow cells were collected for micronuclei analysis.

Seven males per test group were evaluated for the occurrence of micronuclei. Per animal 2000 PCEs were scored for micronuclei. To describe a cytotoxic effect due to the treatment with the test item the ratio between polychromatic and normochromatic erythrocytes was determined in the same sample and reported as the number of PCEs per 2000 erythrocytes. The following dose levels of the test item were investigated: 24 h preparation interval: 500, 1000, and 2000 mg/kg bw; 48 h preparation interval: 2000 mg/kg bw. As estimated by a pre-experiment 2000 mg of the test material per kg b.w. (the maximum guideline-recommended dose) was suitable. The mean number of polychromatic erythrocytes was not decreased after treatment with the test item as compared to the mean value of PCEs of the vehicle control indicating that the test material did not have any cytotoxic properties in the bone marrow. However, the animals showed discoloured urine after treatment with 2000 mg/kg b.w. indicating the bioavailability of the test item. In comparison to the corresponding vehicle controls there was no statistically significant or biologically relevant enhancement in the frequency of the detected micronuclei at any preparation interval and dose level after administration of the test item. The mean values of micronuclei observed after treatment with the test material were near to the value of the vehicle control group. Additionally all values were within the historical vehicle control database. 40 mg/kg b.w. cyclophosphamide administered orally was used as positive control which showed a statistically significant increase of induced micronucleus frequency. In conclusion, the test item did not induce micronuclei as determined by the in-vivo micronucleus test in the bone marrow cells of the mouse.