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Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in mammalian cells
Remarks:
Type of genotoxicity: gene mutation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP and guideline study
Remarks:
Read-across

Data source

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

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
GLP compliance:
yes (incl. QA statement)
Remarks:
testing lab.
Type of assay:
mammalian cell gene mutation assay

Test material

Constituent 1
Reference substance name:
Urea, reaction products with formaldehyde and glyoxal
EC Number:
296-664-6
EC Name:
Urea, reaction products with formaldehyde and glyoxal
Cas Number:
92908-35-5
Molecular formula:
C2 H2 O2 .C H4 N2 O .C H2 O
IUPAC Name:
Urea, reaction products with formaldehyde and glyoxal
Details on test material:
- Name of test material (as cited in study report): Fixapret CP konz., PBG=10073662, after Concentration
- Physical state: liquid
- Analytical purity: 93.4 %
- Lot/batch No.: 000335MCA0

Method

Target gene:
hypoxanthine-guanine phosphoribosyl transferase (HPRT)
Species / strain
Species / strain / cell type:
Chinese hamster lung fibroblasts (V79)
Details on mammalian cell type (if applicable):
- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically checked for karyotype stability: yes
- Periodically "cleansed" against high spontaneous background: yes
Metabolic activation:
with and without
Metabolic activation system:
rat S9 mix (Phenobarbital/ß-naphthoflavone induced)
Test concentrations with justification for top dose:
Experiment 1 (in ug/ml): 100, 200, 400, 800, 1200, 1600 without S9 mix; 100, 200, 400, 800, 1200, 1400 with S9 mix
Experiment 2 (in ug/ml): 2.5; 5.0; 10.0; 20.0; 40.0; 60.0 without S9 mix; 100, 200, 400, 800, 1000, 1200 with S9 mix



Vehicle / solvent:
- Vehicle(s)/solvent(s) used: deionised water
- Justification for choice of solvent/vehicle: The solvent was chosen according to its solubility properties and its relative nontoxicity to the cells. The final concentration of deionised water in the culture medium was 10 % (v/v).
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
Positive controls:
yes
Positive control substance:
other: see remarks
Remarks:
ethylmethane sulfonate 1.2mM without metabolic activation; 7,12-dimethylbenz(a)anthracene with metabolic activation
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Preincubation period: 24 h
- Exposure duration: 4 h/ 24 h
- Expression time (cells in growth medium): 7 days
- Fixation time (start of exposure up to fixation or harvest of cells): 15 days

SELECTION AGENT (mutation assays): thioguanine 11 µg/ml (Sigma)

NUMBER OF REPLICATIONS: 2

Evaluation criteria:
The gene mutation assay is considered acceptable if it meets the following criteria:
- the numbers of mutant colonies per 106cells found in the solvent controls fall within the laboratory historical control data range (see Annex II).
- the positive control substances must produce a significant increase in mutant colony fre-quencies (see Annex II, Historical data).
- the cloning efficiency II (absolute value) of the solvent controls must exceed 50 %.

Statistics:
A linear regression (least squares) was performed to assess a possible dose dependent increase of mutant frequencies using SYSTAT11 (SYSTAT Software, Inc., 501, Canal Boulevard, Suite C, Richmond, CA 94804, USA) statistics software. The number of mutant colonies obtained for the groups treated with the test item were compared to the solvent control groups. A trend is judged as significant whenever the p-value (probability value) is below 0.05. However, both, biological and statistical significance were considered together.

Results and discussion

Test results
Species / strain:
Chinese hamster lung fibroblasts (V79)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not specified
Positive controls validity:
valid
Additional information on results:
No phase separation of the test item was observed up to the maximum concentration in all experimental parts.
Cytotoxic effect as indicated by a relative cloning efficiency I of less than 50 % in both parallel cultures occurred at the maximum evaluated concentration of 1200 g/ml in experiment I with and without metabolic activation following 4 hours of exposure. In experiment II cytotoxic effects as described above were observed at the maximum evaluated concentration of 60 g/ml without metabolic activation (24 hours treatment) and at 800 g/ml and above with metabolic activation (4 hours treatment). The relative cloning efficiency I covered the recommended cytotoxic range of approximately 10-20% with and without metabolic activation.
No relevant and reproducible increase in mutant colony numbers/106cells was observed in the main experiments up to the maximal concentration. The mutant frequency remained well within the historical range of solvent controls. The induction factor exceeded the threshold of three times the corresponding solvent control in the first culture of the first experiment at 1200 g/ml with metabolic activation. This isolated increase was judged as biologically irrelevant since it was not reproduced in the parallel culture performed under identical conditions, and the total number of mutant colonies/106cells did not exceed the range of the historical solvent control values. Furthermore, the isolated increase was not dose dependent as indicated by the lacking statistical significance.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:
In conclusion it can be stated, that under the experimental conditions reported the test item did not induce gene mutations at the HPRT locus in V79 cells.