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Genetic toxicity in vitro

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Reference
Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1986/87
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
S. typhimurium TA 1538
Metabolic activation:
with and without
Metabolic activation system:
rat liver S9 mix
Test concentrations with justification for top dose:
Experiment I and II: 5000, 1000, 200, 40, 8.0, 1.6 µg/plate
Experiment III: 5000, 2500, 1000, 500, 200, 100 µg/plate
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
9-aminoacridine
other: 2-aminoanthracene, daunomycin, 4-nitro-o-phenylenediamine, N-methyl-N'-nitro-N-nitrosoguanidine
Evaluation criteria:
A positive response in an experiment is achieved when a two-fold or greater increase in the mean number of revertant colonies per test plate (over and above that observed for the solvent control plates) is obtained at at least one dose level. A second criterion for a positive result is the observation of a statistically significant dose-related increase in the number of revertants. In either case, the observed effect should be reproducible.
Statistics:
The calculations of the mean colony count/plate and the standard deviation were carried out by computer.
An assessment of the statistical significance was carried out using a one-tailed Student's t-test (Ehrenberg 1984). The corresponding probability for each dose level was determined from a t-table using the appropriate degrees of freedom.
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1538
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
In experiment 1, the compound induced an increase in observed revertant colony numbers in strain TA1538 (+S9), reaching a maximum response of 2.1x the background mutation rate at 200 µg/plate. This response was without dose-relationship, but was highly statistically significant (p<0.005 at 1000 and 200 µg/plate). In the second experiment, again an increase in mutation frequency that was not dose-related was observed in strain TA1538 (+S9) reaching 2.05x the background mutation rate at 1000 µg/plate. In a third experiment over the narrower dose range of 5000-100 µg/plate, a slight increase in revertant colony numbers was again observed in strain TA1538 (+S9), reaching a maximum of 1.75x the background mutation rate at 1000 µg/plate without however reaching the 2-fold level.
Conclusions:
he test substance was considered not to be mutagenic in the Salmonella mutagenicity assay.
Executive summary:

A Test Sample of Substance H111567 has been evaluated in the Salmonella mutagenicity assay of Maron and Ames (1983).

In two separate experiments, the Test Sample did not induce any significant reproducible increases in the observed numbers of revertant colonies in any of the tester strains used (TA1535, TA1537, TA1538, TA98 and TA100) in the absence of any auxiliary metabolising system (S9), nor in strains TA1535, TA1537, TA98 and TA100 in the presence of S9.

In experiment 1, the compound induced an increase in observed revertant colony numbers in strain TA1538 (+S9), reaching a maximum response of 2.1x the background mutation rate at 200 µg/plate. This response was without dose-relationship, but was highly statistically significant (p<0.005 at 1000 and 200 µg/plate). In the second experiment, again an increase in mutation frequency that was not dose-related was observed in strain TA1538 (+S9) reaching 2.05x the background mutation rate at 1000 µg/plate. In a third experiment over the narrower dose range of 5000-100 µg/plate, a slight increase in revertant colony numbers was again observed in strain TA1538 (+S9), reaching a maximum of 1.75x the background mutation rate at 1000 µg/plate without however reaching the 2-fold level. However, although a very slight effect was observed in all three assays in strain TA1538 (+S9), both criteria for a positive result were not obtained in these experiments. The test substance was hence considered not to be mutagenic in the Salmonella mutagenicity assay.

Genetic toxicity in vivo

Description of key information

XXXX

Additional information

Justification for classification or non-classification

Based on the results of a reverse mutation assay, the test substance XXXX.