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Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study performed under GLP, well reported with many details on the results acceptable for the assessment of the endpoint. Include also the Prival and Mitchell procedure for mutagenicity.
Justification for type of information:
Justification for read across is detailed in the report attached to the IUCLID section 13.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2016
Report Date:
2016

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Test material form:
solid: particulate/powder

Method

Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium, other: TA 98, TA 100, TA 1535, TA 1537
Details on mammalian cell type (if applicable):
Bacterial strains: The bacterial tester strains Salmonella typhimurium TA 1535 (CCM 3814, lot. No. 2101200916917), TA 98 (CCM 3811, lot No. 01022001220053), TA 100 (CCM 3812, lot No. 0102201220054) and TA 1537 (CCM 3815, lot No. 2101200916918) as well as Escherichia coli WP2 uvrA (CCM 4751, lot No. 2104200512732), - were obtained from Czech Collection of Microorganisms (CCM) of Masaryk University, Brno. Strains TA 98 and TA 1537 detect frame shift mutations, strains TA 100 and TA 1535 serve to detection of base-pair substitution mutations, and strain E.coli WP2 uvrA detects cross-linking mutagens. Genotypes of strains: Genotypes of each strain were controlled (plasmid pKM 101 – ampicillin resistance, uvr mutation, rfa mutation, his/trp mutation – spontaneous reversions).
Additional strain / cell type characteristics:
other: see details above
Species / strain / cell type:
E. coli WP2 uvr A
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
rat liver S9 mix
Test concentrations with justification for top dose:
50, 100, 500, 1500 and 5000.0 µg/plate

Selection of doses/toxicity: The test substance was dissolved in water for injection till the maximum recommended concentration 5000 μg per 0.1 mL. For toxicity experiment the highest concentration was diluted to the other 5 concentrations in 3 digit places interval. Although no particles could be observed in higher concentrations due to dark colour of solutions, no particles were observable in top agar and Petri dishes. The concentration row was tested for toxicity in strain TA 100 without metabolic activation (see Table B). No toxicity or precipitation was observed in any dose. The concentration of 5000 µg. 0.1 mL-1 was then used as maximum in the first mutagenicity experiments. Further doses were diluted with factor approximately 2-√10. Mutagenicity occurred in some cases in higher doses so lower concentrations were omitted and generally higher concentrations were used in the second mutagenicity experiments. For increase of sensibility, the second experiments were performed with preincubation for 30 minutes at 37±1°C and shaking. Fresh solutions of the test substance were prepared before each experiment. Concentrations of the test substance solution were dosed in the volume of 0.1 mL per plate.
Vehicle / solvent:
injection water
Controlsopen allclose all
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
sodium azide
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
other: 4-nitro-o-phenylenediamine (NPD)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
other: 9-aminoacridine hydrochloride monohydrate (9-AAc)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
other: N-methyl-N´-nitro-N-nitrosoguanidine (MNNG)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene (2-AA)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
other: 2-aminofluorene (2-AF)
Details on test system and experimental conditions:
Preparation and using of S9:
The metabolic activation was performed by S9 fraction of rat liver homogenate and mixture of cofactors. The liver homogenate was prepared from Wistar male rats weighing approximately 200 g, previously induced with Delor 106 (mixture of PCBs). Delor 106 was diluted with olive oil to a concentration of 200 mg·mL-1, and each rat was administered a single injection of 500 mg/kg 5 days before S9 preparation. The S9 was prepared according to the methods described by Maron and Ames (1983). The liver was removed from each animal and washed in ice cold 0.15M KCl. The livers washed were mixed with another 0.15 M KCl (3 mL.g-1 wet liver) homogenized in a grinder, and the tissue suspension was centrifuged for 10 min at 9000 g. Aliquots of the supernatant (S9) were stored in plastic tubes using sterile technique at a temperature below –70 C. Cofactors (NADP and glucoso-6-phosphate) were dissolved in buffer. Each plate in all experiments with metabolic activation contained 0.5 mL of buffer with NADP and glucoso-6-phosphate and 30 or 100 L S9 (the concentration of S9 in the S9mix was 5.7 or 19%). In experiments without metabolic activation only buffer was added to the top agar.

Plate Incorporation Test:
Test procedure: 100 µ.L of the test substance of required concentration, 100 µ.L of 16-18 h culture of tester strain of density 108-109 CFU/mL, 0.5 mL relevant buffer and 30, 50 or 100 µL of S9 post mitochondrial fraction (in case of test with metabolic activation) were added to the 2 mL of molten top agar (with trace of histidine or tryptophan) kept in a test tube at 453C. After shaking the mixture was poured into a minimal glucose agar plate. Petri dishes were incubated of 48 - 72 h at 37 °C, the number of revertant colonies on the plate was counted manually with exception of positive controls, which were counted by an AccuCount 1000. For an adequate estimate of variation, triplicate plating was used at each dose level. The toxicity test, which serves for finding of optimal concentrations for the mutagenicity test, was performed in strain TA 98 and two Petri dishes were used for every concentration.
Evaluation criteria:
The main criterion for evaluation of results was modified two-fold increase rule, which is compatible with the application of statistical methods (2, 3). After this rule the result is positive, if a reproducible dose-response effect occurs and/or a doubling of the ratio Rt/Rc is reached. An increase is considered as ”biologically relevant“: - if the number of reversions is at least twice as high as that in the solvent control for the strains having spontaneous reversion >10; - if the number of reversions is at least three times as high as that in the solvent control for the strains having spontaneous reversion ≤10; A test substance producing neither a dose-related increase in the number of revertants nor a reproducible biologically relevant positive response at any of the dose groups is considered to be non-mutagenic in this system.
Statistics:
According to OECD TG 471, the biological relevance of the results is the criterion for the interpretation of results, a statistical evaluation of the results is not regarded as necessary.

Results and discussion

Test resultsopen allclose all
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
positive
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
positive
Cytotoxicity / choice of top concentrations:
not specified
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:
other: slightly mutagenic
Cytotoxicity / choice of top concentrations:
not specified
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:
not specified
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1535
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
Additional information on results:
See attached document for a complete evaluation of the results.

Applicant's summary and conclusion

Conclusions:
Based on the evaluation of the test rsults, the substance is considered as not mutagen.
Executive summary:

The study was perfomed according to OECD 471 and showed the following results:

negative for strains TA1535 and TA98

slightly mutagenic for strain TA100

mutagenic for strain TA1537 and Escerichia Coli