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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro DNA damage and/or repair study
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
Deviations to OECD 482: slight differences in protocol, no evaluation criteria are reported

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1980
Report Date:
1980

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Test performance comparable to OECD 482 (deleted in 2014)
GLP compliance:
not specified
Type of assay:
DNA damage and repair assay, unscheduled DNA synthesis in mammalian cells in vitro

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
Source: Sigma-Aldrich
Batch no.: 13975

Method

Target gene:
human fibroblasts
Species / strain
Species / strain / cell type:
other: human fibroblasts (diploid)
Metabolic activation:
with and without
Metabolic activation system:
rat liver S-9 mix
Test concentrations with justification for top dose:
up to 9.48 mg/ml of culture medium
Vehicle / solvent:
dimethylsulphoxide
Controls
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: Ethyl methanesulphonate ( EMS)

Results and discussion

Test results
Key result
Species / strain:
other: human fibroblasts (diploid)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
In the initial assay involving tritiated thymidine incorporation into non-S phase cells, there was no indication of any significant increase in the number if silver grain per nucleus at any concentration of cyclohexanone. The highest concentration used in this test was 10 µl, or 9.478 mg/mL. The positive control substances used, 4-nitroquinoline- N-oxide and 2-aminoanthracene, induced significant responses in unscheduled DNA synthesis in these cells. Some of the mean grain counts per nucleus were rather high in this first experiment, so, it was repeated At a dose level of 74 µg/mL in the presence of S9 mix there was a high result, but the standard deviation also was very high. These experiments gave no indication of UDS induction. These positive control substances, however, are not appropriate for the demonstration of short patch repair when measured by Method 2. The tritiated deoxyguanosine incorporation assay was used to confirm the results of the first assay. During the course of these experiments, the permeability of both cell lines to deoxyguanosine decreased greatly, this reduction being aggravated by the addition of S9 mix to the incubation medium. In consequence, the measured incorporation of radioactivity was insufficient to provide any reasonable analysis of data produced.

Applicant's summary and conclusion

Conclusions:
Only minor deviations to the OECD guideline 482 (deleted in 2014) were obvious in the NIOSH study. A negative result in an UDS assay employing human fibroblasts in concentrations up to 9.48 mg/mL (with and without metabolic activation) was reported. This negative outcome was confirmed in an independent experimental repeat.