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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro cytogenicity / chromosome aberration study in mammalian cells
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant guideline study, available as unpublished report, no restrictions, fully adequate for assessment.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report Date:
2005

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
Qualifier:
according to
Guideline:
EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)
Qualifier:
according to
Guideline:
other: Japanese Guideline: Kanpoan No. 287 - Environmental Agency
Qualifier:
according to
Guideline:
other: Japanese Guideline: Eisei No. 127 - Ministry of Health & Welfare
Qualifier:
according to
Guideline:
other: Japanese Guideline: Heisei 09/10/31 Kikyoku No. 2 - Ministry of International Trade & Industry
GLP compliance:
yes (incl. certificate)
Remarks:
RCC Cytotest Cell Research GmbH, In den Leppsteinwiesen 19, D-64380 Roßdorf
Type of assay:
in vitro mammalian chromosome aberration test

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): FAT 40821/A
- Purity: Approx. 81%
- Lot/batch No.: TVR1
- Expiration date: 1 February 2010
- Storage condition: At room temperature. Protected from moisture (exsiccator).

Method

Species / strain
Species / strain:
Chinese hamster lung fibroblasts (V79)
Metabolic activation:
with and without
Metabolic activation system:
Phenobarbital/ß-Naphthoflavone induced rat liver S9
Test concentrations with justification for top dose:
- Without S9 mix: 15.6, 31.3, 62.5, 125, 250, 500 µg/mL
- With S9 mix: 31.3, 62.5, 125, 250, 500, 1000 µg/mL
Vehicle:
Deionised water. The final concentration of deionised water in the culture medium was 10 % (v/v).
Controlsopen allclose all
Negative controls:
yes
Remarks:
culture medium
Solvent controls:
yes
Remarks:
deionised water
True negative controls:
no
Positive controls:
yes
Positive control substance:
ethylmethanesulphonate
Remarks:
Without metabolic activation
Negative controls:
yes
Remarks:
culture medium
Solvent controls:
yes
Remarks:
deionised water
True negative controls:
no
Positive controls:
yes
Positive control substance:
cyclophosphamide
Remarks:
With metabolic activation
Details on test system and conditions:
METHOD OF APPLICATION: in medium

RANGE-FINDER
A pre-test on cell growth inhibition with 4 hrs and 24 hrs treatment was performed in order to determine the toxicity of the test item. Cytotoxicity was determined using concentrations separated by no more than a factor of 2 - √10. The general experimental conditions in this pre-test were the same as described below for the cytogenetic main experiment. The following method was used: In a quantitative assessment, exponentially growing cell cultures (seeding about 46,000 cells/ slide, with regard to the culture time 48 hrs) were treated with the test item for simulating the conditions of the main experiment. A qualitative evaluation of cell number and cell morphology was made 4 hrs and 24 hrs after start of treatment. The cells were stained 24 hrs after start of treatment. Using a 400 fold microscopic magnification the cells were counted in 10 coordinate defined fields of the slides (2 slides per treatment group).

EXPERIMENTAL PERFORMANCE
- Exponentially growing stock cultures more than 50 % confluent are treated with trypsin-EDTA-solution at 37°C for approx. 5 minutes. Then the enzymatic treatment is stopped by adding complete culture medium and a single cell suspension is prepared. The trypsin concentration for all subculturing steps is 0.5 % (w/v) in Ca-Mg-free salt solution (Invitrogen GIBCO, D-76131 Karlsruhe). Prior to the trypsin treatment the cells are rinsed with Ca-Mg-free salt solution. The cells were seeded into Quadriperm dishes (Heraeus, D-63450 Hanau) which contained microscopic slides (at least 2 chambers per dish and test group). In each chamber 1E4 - 6E4 cells were seeded with regard to the preparation time. The medium was MEM with 10 % FCS (complete medium).
- Exposure duration: The culture medium of exponentially growing cell cultures was replaced with serum-free medium (for treatment with S9 mix) or complete medium (for treatment without S9 mix) with 10 % FCS (v/v), containing the test item. For the treatment with metabolic activation 50 µL S9 mix per mL medium were used. Concurrent negative, solvent, and positive controls were performed. After 4 hrs the cultures were washed twice with "Saline G" and then the cells were cultured in complete medium for the remaining culture time.
- Preparation of the cultures: Colcemid was added (0.2 µg/mL culture medium) to the cultures 15.5 hrs after the start of the treatment. The cells on the slides were treated 2.5 hrs later in the chambers with hypotonic solution (0.4 % KCl) for 20 min at 37° C. After incubation in the hypotonic solution the cells were fixed with a mixture of methanol and glacial acetic acid (3:1 parts, respectively). Per experiment two slides per group were prepared. After preparation the cells were stained with Giemsa (E. Merck, D-64293 Darmstadt).
- Evaluation of Cell Numbers: For evaluation of cytotoxicity indicated by reduced cell numbers additional two cultures per test item and solvent control group, not treated with colcemid, were set up in parallel. These cultures were stained after 18 hrs, in order to determine microscopically the cell number within 10 defined fields per coded slide. The cell number of the treatment groups is given in percentage compared to the respective solvent control.
- Analysis of Metaphase Cells: Evaluation of the cultures was performed (according to standard protocol of the "Arbeitsgruppe der Industrie, Cytogenetic') using NIKON microscopes with 100x oil immersion objectives. Breaks, fragments, deletions, exchanges, and chromosome disintegrations were recorded as structural chromosome aberrations. Gaps were recorded as well but not included in the calculation of the aberration rates. 100 well spread metaphase plates per culture were scored for cytogenetic damage on coded slides, except for the highest evaluated concentration in Experiment I in the absence of metabolic activation, where 200 metaphase plates were scored. Only metaphases with characteristic chromosome numbers of 22 ± 1 were included in the analysis. To describe a cytotoxic effect the mitotic index (% cells in mitosis) was determined. In addition, the number of polyploid cells in 500 metaphase cells per culture was determined (% polyploid metaphases; in the case of this aneuploid cell line polyploid means a near tetraploid karyotype).
Evaluation criteria:
- Acceptability of the test: The chromosome aberration test performed in our laboratory is considered acceptable if it meets the following criteria: a) The number of structural aberrations found in the negative and/or solvent controls falls within the range of our historical laboratory control data: 0.0 - 4.0 % aberrant
cells, exclusive gaps. b) The positive control substances should produce significant increases in the number of cells with structural, chromosome aberrations, which are within the range of the laboratory's historical control data.
- Evaluation of results: A test item is classified as non-clastogenic if: the number of induced structural chromosome aberrations in all evaluated dose groups is in the range of our historical control data (0.0 - 4.0 % aberrant cells, exclusive gaps); and/or no significant increase of the number of structural chromosome aberrations is observed.
A test item is classified as clastogenic if: the number of induced structural chromosome aberrations is not in the range of the historical control data (0.0 - 4.0 % aberrant cells, exclusive gaps); and either a concentration-related or a significant increase of the number of structural chromosome aberrations is observed.
A test item can be classified as aneugenic if: the number of induced numerical aberrations is not in the range of our historical control data (0.0 - 8.5 % polyploid cells).
Statistics:
Statistical significance was confirmed by means of the Fisher's exact test (p < 0.05). However, both biological and statistical significance should be considered together.

Results and discussion

Test resultsopen allclose all
Species / strain:
Chinese hamster lung fibroblasts (V79)
Metabolic activation:
without
Genotoxicity:
positive
Cytotoxicity:
yes
Vehicle controls valid:
yes
Negative controls valid:
yes
Positive controls valid:
yes
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Species / strain:
Chinese hamster lung fibroblasts (V79)
Metabolic activation:
with
Genotoxicity:
negative
Cytotoxicity:
yes
Vehicle controls valid:
yes
Negative controls valid:
yes
Positive controls valid:
yes
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Additional information on results:
RANGE FINDING STUDY: In a range finding pre-test on toxicity cell numbers were scored 24 hrs after start of treatment as an indicator for cytotoxicity. Concentrations between 46.9 and 6000 µg/mL were applied. Clear toxic effects were observed after 4 hrs and 24 hrs treatment with 375 µg/mL and above in the absence of S9 mix. In the presence of S9 mix, treatment with 750 µg/mL and above induced strong toxic effects.

TEST-SPECIFIC CONFOUNDING FACTORS: In the pre-experiment, precipitation of the test item in culture medium was observed after 4 hrs treatment at 375 µg/mL and above and after 24 hrs treatment at 750 µg/mL and above in the absence of S9 mix. In the presence of S9 mix, precipitation was observed after treatment with 93.8 µg/mL and above. No relevant influence of the test item on the pH value or osmolarity was observed (solvent control 286 mOsm, pH 6.9 versus 306 mOsm and pH 7.4 at 6000 µg/mL). However, the slight increase in the pH value has to be regarded as being irrelevant since no influence on the pH value in the main experiment was observed (solvent control 316 mOsm, pH 7.4 versus 303 mOsm and pH 7.4 at 500 µg/mL).
In the main experiment, in the absence of S9 mix, precipitation of the test item was observed after treatment with 500 µg/mL In the presence of S9 mix, precipitation of the test item in culture medium was observed with 250 µg/mL and above.

MAIN TEST: In the cytogenetic experiment, in the absence of S9 mix, a statistically significant and biologically relevant increase in the number of cells carrying structural chromosome aberrations was observed at the highest evaluated concentration (8.25 % aberrant cells, exclusive gaps, at 250 µg/mL). This value clearly exceeded the respective solvent control value (2.0 % aberrant cells, exclusive gaps) and the range of our historical control data: 0.0 - 4.0 % aberrant cells, exclusive gaps. The increase in the number of cells carrying exchanges (3.75 %) gives additional evidence for a clastogenic potential of the test item. In addition, in this experimental part the aberration rates were dose-dependent increased (3.0 %, 3.5 %, and 8.25 % aberrant cells, exclusive gaps) in the concentration range scored for cytogenetic damage (62.5 to 250 µg/mL). Therefore, the statistical significance and the dose-dependency have to be regarded as being biologically relevant. In the presence of S9 mix, a dose-dependent increase in the aberration rate was observed in the tested concentration range (62.5 to 250 µg/mL). The values (2.0 %, 2.5 %, and 4.0 % aberrant cells, exclusive gaps) were within our historical control data range (0.0 - 4.0 % aberrant cells, exclusive gaps) and showed no statistical significance. Therefore, this observation in the presence of S9 mix has to be considered as being biologically irrelevant. No biologically relevant increase in the rate of polyploid metaphases was found after treatment with the test item (0.4 - 1 .6 %) as compared to the rates of the solvent controls (1.2-2.1 %).

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
positive without metabolic activation

Under the experimental conditions reported, the test substance did induced structural chromosome aberrations in V79 cells (Chinese
hamster cell line) in the absence of S9 mix.
Executive summary:

In a GLP compliant chromosome aberration test, tested according to OECD guideline 473, Chinese hamster V79 cells, were exposed to the test substance, with and without metabolic activation by S9 mix. The exposure period was 4 hours with and without metabolic activation. In each experimental group two parallel cultures were set up. Per culture 100 metaphase plates were scored for structural chromosome aberrations. Dose selection of the main experiments was based on a pretest. Toxic effects indicated by reduced mitotic indices or reduced cell numbers were observed after treatment with the test item. However, concentrations showing clear cytotoxicity were not scorable for cytogenetic damage. In the absence of S9 mix, a dose-related increase in the number of cells carrying structural chromosomal aberrations was observed with a statistically significant and biologically relevant value after treatment with the test item in the highest evaluable concentration (250 µg/mL), clearly exceeding historical control data range. In addition, the number cells carrying exchanges was distinctly increased. No relevant increase in the frequencies of polyploid metaphases was found after treatment with the test substance as compared to the frequencies of the controls. In conclusion, it can be stated that under the experimental conditions reported, the test item did induce structural chromosome aberrations. Therefore, the test substance is considered to be clastogenic.