Registration Dossier

Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Salmonella mutagenicity tests: V. Results from the testing of 311 chemicals
Author:
Zeiger E et al.
Year:
1992
Bibliographic source:
Environ Mol Mutagen 19; Suppl 21:2-141

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Bacterial cultures were grown overnight at 37C with shaking in Oxoid 2 broth supplemented wiht biotin (0.8 ug/ml) and histidine (40ug/ml). For metabolic activation S-9 Aroclor 1254-induced, male Sprague-Dawley rat and Syrian hamster livers were used. The top agar was added and poured onto surface of petri dishes containing Vogel-Bonner medium. Histidine-independent colonies arising on these plates were counted following two days incubation at 37C. Plates were machine counted. The test chemical was initially tested in the preincubation test at half-log dose intervals up to a dose tha elicited toxicity, or to a dose immedelately below on the was toxic in the preliminary toxicity procedure. Test item was tested as triplicates. Concurrent solvent and positive controls were run at each trial.
GLP compliance:
not specified
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline
Specific details on test material used for the study:
6-Methyl-2-thiouracil, CAS nro.56-04-2. Supplier: Aldric. Analyzed purity 99%.

Method

Species / strainopen allclose all
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain:
S. typhimurium TA 1538
Test concentrations with justification for top dose:
10,33, 100, 333, 1000, 333, 10000 ug/plate. Bacterial toxicity was used as a selection of top dose
Vehicle:
DMSO
Controls
Negative controls:
yes
Remarks:
DMSO
Solvent controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
sodium azide
methylmethanesulfonate
mitomycin C
other: 4-nitro-o-phenylenediamine
Details on test system and conditions:
The initial test of a chemical was done without activation and with 10% S-9. If a positive result was obtained, the postitive trials were repeated. If trials were negative the chemical was retested without S-9 and with 30% S-9. Tf all trials were negative, no further testing was performed.
Evaluation criteria:
Individual trials were judged mautgenic, weakly mutagenic, questionable or nonmutagenic, depending on the magnitude of His+ revertants, and the shape of the dose-response. A trial was considered questionable if the dose-response was judged insufficientrly high to support a call of weakly mutagenic, if only a single dose was elevated over the control, or if a weak increase was not dose-related. The distinctions betweem a questionable response and a nonmutagenic or weakly mutagenic response, and between a weak mutagenic response, and betweem and between a weak mutagenic respons and mutagenic respons are highlty subjective. It was not necessary for a response to reach two-fold over nackground for a trial to be judged mutagenic.
A chemical was judged mutagenic or weakly mutagenic if it produced a reproducible, dose-related response over hte solvent control, under a single metabolic activation condition, in replicate trials. A chemical was judged questionable if the results of individual trials were not reproducible, if increases in His+ revertants did not meet the criteria for a weakly mutagenic response, or if only single doses produceed increases in His+ revertants in repeated trials. Chemicals were judged nonmutagenic if they did not meet the criteria for a mutagenic or questionable response.

Results and discussion

Test resultsopen allclose all
Key result
Species / strain:
S. typhimurium TA 97
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Vehicle controls valid:
yes
Negative controls valid:
not applicable
Positive controls valid:
yes
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Vehicle controls valid:
yes
Negative controls valid:
not applicable
Positive controls valid:
yes
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Vehicle controls valid:
yes
Negative controls valid:
not applicable
Positive controls valid:
yes
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Vehicle controls valid:
yes
Negative controls valid:
not applicable
Positive controls valid:
yes

Applicant's summary and conclusion

Conclusions:
In Salmonella mutation test with methylthiouracil no revertant mutations was observed.
Executive summary:

Salmonella mutation test was performed using strains TA 97, TA 97, TA 100 and TA 1535 with concentrations 10, 33, 100, 33, 1000, 3333, and 10 000 ug/plate.

Compared to the solvent control no two-fold or more in number of revertant clones were observed in any strains and concentrations tested.