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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
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:
Evaluation of feasibility of mutagenic testing of shale oil products and effluents
Author:
Epler JL, Rao TK, Guerint MR
Year:
1979
Bibliographic source:
Environ Health Perspect 30, 179-184

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
Method described by Ames et al.: Ames BN, McCann J, Yamasaki E (1975) Methods for detecting carcinogens and mutagens with the Salmonella / mammalian-microsome mutagenicity test. Mutat Res 31, 347.
Deviations:
yes
Remarks:
Only S. typhimurium strains TA 98 and TA 100 have been tested.
GLP compliance:
no
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline

Method

Target gene:
TA98: hisD3052, uvrB, rfa (frameshift plus R factor)
TA100: his G46, uvrB, rfa (missense plus R factor)
Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 98
Species / strain / cell type:
S. typhimurium TA 100
Metabolic activation:
with and without
Metabolic activation system:
S-9 mix prepared from rat livers induced with Aroclor 1254
Test concentrations with justification for top dose:
All shale oil fractions and compounds examined were tested with the plate assay over at least a 1000-fold concentration range with the two tester strains TA98 and TA100. Positive or questionable results were retested with a narrower range of concentrations.
Vehicle / solvent:
Compounds to be tested were suspended in dimethylsulfoxide (DMSO, supplied sterile, spectrophotometric grade from Schwarz/Mann) to concentrations in the range 10-20 mg/ml.
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
not specified
Details on test system and experimental conditions:
The strain to be treated with the potential mutagen was added to soft agar containing a low level of histidine and biotin along with varying amounts of the test substance. The suspension containing approximately 2 x 10E8 bacteria was overlaid on minimal agar plates, and revertants to wild type were counted after a 48-hour incubation period. The studies were carried out with parallel series of plates plus and minus a rat liver enzyme preparation for metabolic activation (S9-mix). The potential mutagen was in some cases assayed for general toxicity, which was indicated by bacterial survival, with strain TA1537.
Evaluation criteria:
Revertant colonies were counted after 48 hours of incubation.
Statistics:
The recorded numbers of revertant colonies were plotted versus respective concentrations of 2,5-xylenol, and the slopes of the induction curves were determined.

Results and discussion

Test resultsopen allclose all
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid

Applicant's summary and conclusion

Conclusions:
2,5-Xylenol showed no mutagenic potential in the bacterial reversion mutation assay using S. typhimurium strains TA 98 and TA 100, both with and without metabolic activation.
Executive summary:

Shale oil fractions and known constituents such as 2,5-xylenol were examined in the in vitro bacterial reversion mutation assay (Ames test) using Salmonella typhimurium strains TA 98 and TA 100, both with and without a rat liver enzyme preparation for metabolic activation (S-9 mix). The test was well documented and the procedure was similar to OECD Guideline 471. Over a 1000-fold concentration range of the test material, no increase of revertant colonies was noted. Thus, 2,5-xylenol showed no mutagenic potential in this test.