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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in mammalian cells
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1996-08-19 to 1996-10-17
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996
Report Date:
1996

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Version / remarks:
1984
GLP compliance:
yes (incl. certificate)
Type of assay:
mammalian cell gene mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Method

Target gene:
HPRT
Species / strain
Species / strain / cell type:
Chinese hamster Ovary (CHO)
Metabolic activation:
with and without
Metabolic activation system:
Aroclor induced rat liver S9
Test concentrations with justification for top dose:
with S9: 18, 60, 180, 600, and 1800 µg/ml; without S9: 10, 30, 100, 300 and 1000 µg/ml
Controlsopen allclose all
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
ethylmethanesulphonate
Remarks:
without activation
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-(20)-methylcholanthrene
Remarks:
with activation
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Preincubation period: none
- Exposure duration:4 h with and without S9
- Expression time (cells in growth medium): 20 hours
- Selection time (if incubation with a selection agent): 7 days

SELECTION AGENT (mutation assays): H10 medium

NUMBER OF REPLICATIONS: experiment was repeated. 3 plates per culture were used for evaluation of mutagenicity

NUMBER OF CELLS EVALUATED: 3 x 200 cells per culture seeded to plates. Stained with Giesma before counting

DETERMINATION OF CYTOTOXICITY
- Method: cloning efficiency



Evaluation criteria:
Positive if causes statistically significant dose related increase in mutant frequency at concentrations resulting in greater than 20% cell survival, reaching a value above the maximum spontaneous mutant frequency.

Results and discussion

Test results
Species / strain:
Chinese hamster Ovary (CHO)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
other: >1800 ug/plate without S9; some cytotoxicity noted at all concentrations with S9
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH:
- Effects of osmolality:
- Evaporation from medium:
- Water solubility:
- Precipitation:
- Other confounding effects:

RANGE-FINDING/SCREENING STUDIES:
Results of preliminary study:In the absence of S9 mix, treatment with Dynasylan VTMO concentrations up to 1800µg/ml had no significant influence on the cloning efficiency, while at the next higher dose (3000  µg/ml) no viable cells were left.  In the presence of S9, all treatments with Dynasylan VTMO resulted in cytotoxicity. 

COMPARISON WITH HISTORICAL CONTROL DATA: solvent controls were low (0-4 0-20 mutants/10E6 cells) in comparison with historical controls (0-20 0-20 mutants/10E6 cells)

ADDITIONAL INFORMATION ON CYTOTOXICITY:

Any other information on results incl. tables

In the two independent experiments of the main study, the mutant frequencies of the negative controls (culture medium) were consistent with historical control data for this test system (i.e. 0-20 mutants/10E6 cells).  Treatment of CHO
cells with the positive controls, 3-methylcholanthrene (with S9 mix) or ethyl methane sulfonate (without S9 mix) resulted
in highly significant increases of the mutant frequencies of the HPRT locus, thus demonstrating the sensitivity of the
test system and the activity of the S9 mix.

In the main study, treatment of CHO cells with Dynasylan VTMO in each of two independent experiments did not result
in biologically significant increases of the mutant frequency of the HPRT locus.  Statistically significant
increases (as compared to the low concurrent negative controls of 0 to 4 mutants/10E6 viable cells) were observed
with a number of test compound concentrations.  However, these were within the range of historical laboratory
negative controls and did not show a dose-response relationship.  These mutant frequencies were considered to
be the result of normal assay variation and not indicative of a mutagenic effect of Dynasylan VTMO.

Applicant's summary and conclusion

Conclusions:
Trimethoxyvinylsilane has been tested in a valid study according to OECD TG 476 and under GLP. No statistically significant dose related increases in the number of revertants was observed either with or without activation. It is concluded that the test substance is negative for mutagenicity to mammalian cells under the conditions of the study.