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Genetic toxicity in vitro

Description of key information

Bacterial reverse mutation assay/Ames test: negative (OECD 471; GLP)

Link to relevant study records

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Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2001-11-15 to 2002-06-07
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
significant methodological deficiencies
Remarks:
Deviations from the OECD 471 (1997): titre demonstration was invalid for two strains (still these values were used for the cytotoxicity determination); spontaneous revertants counts were not for all strains within historical controls given by the laboratory; historical controls for the spontaneous revertants were only given for cultures without S9 mix; cytotoxicity was only determined without S9 mix and for the highest concentration tested; cytotoxicity was seperately tested and not within the plates used for determining mutagenicity; determination of cytotoxicity was not plausible; second experiment used only one concentration instead of five concentration; positive control with metabolic activation was only included for one strain (TA98); historical data for the positive control are missing
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1997-07-21
Deviations:
yes
Remarks:
please refer to the field "Rationale for reliability incl. deficiencies" above
GLP compliance:
yes (incl. QA statement)
Remarks:
inspection of laboratory: 1999-02-09
Type of assay:
bacterial reverse mutation assay
Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: test material was kept in a closed polyethylene vessel in the dark in a refrigerator
Target gene:
TA97a: hisD6610
TA98: hisD3052
TA100 and TA1535: hisG46
TA102: hisG428
Species / strain / cell type:
S. typhimurium, other: TA1535, TA97a, TA98, TA100, and TA102
Metabolic activation:
with and without
Metabolic activation system:
S9-mix (containing approx. 4 % S9; 2.0 mL): sodium-ortho-phosphate buffer (25.0 mL; pH 7.4); NADP (2 mL); glucose-6-phosphate (0.25 mL); saline solution (1.0 mL); water, dest. steril: 19.75 mL
Test concentrations with justification for top dose:
Experiment 1: 0.15, 0.5, 1.5, 5, and 15 µg/plate (with and without metabolic activation)
Experiment 2: 5.5 µg/plate (with and without metabolic activation)
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: water
Experiment 1: sterile filtration of the resulting saturated solution was performed and the solution was further diluted.
Experiment 2: the test substance was dissolved in water. This was done by weighing in an excess, treatment with ultrasound, warming, shaking and subsequent filtration of the resulting solution. The solution was further diluted.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
Remarks:
water
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
benzo(a)pyrene
cumene hydroperoxide
other: 4-Nitro-1,2-phenylendiamin (without metabolic activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

EXPERIMENTAL PERFROMANCE
- 0.1 mL of the test substance solution was pipetted into a sterile tube preheated to 45 ° C.
- then, the tube was filled up with 2 mL of top agar, followed by adding 0.1 mL of bacteria suspension and 0.5 mL of phosphate buffer (testing without S9) or 0.5 mL of S9 mix (testing with S9).
- after short panning, tube content was poured onto a minimal glucose plate and the mixture was evenly spread with a Drigalski spatula.
- the plate was closed and covered with brown paper (for protection against UV radiation) and left on a flat surface until the agar solidifies
- after solidification, the plate was turned over and placed into a dark, 37 °C hot incubator.
- incubation lasted 48 hours
- number of revertants/plate were counted

Validation of the genotype, determination of titer, and control of sterility were also carried out.

NUMBER OF REPLICATIONS: quadruplicate

DETERMINATION OF CYTOTOXICITY
Each strain was tested with the test substance at its maximum concentration (experiment 1: 15 µg/plate; experiment 2: 5.5 µg/plate) without metabolic activation.
Rationale for test conditions:
not specified
Evaluation criteria:
A test substance is considered to be mutagenic, if in at least one of the strains used, with or without S9 mix, a twofold increase in mutant numbers compared to the negative control is induced (induction rate I ≥ 2) or shows a concentration-response relationship.
Statistics:
The evaluation of the data was carried out by using a spreadsheet program (Microsoft Excel®). The induction rates were tabulated against the dilution of the test substance.
Key result
Species / strain:
S. typhimurium, other: TA1535, TA97a, TA98, TA100, and TA102
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
Experiment 1: at the maximum dose of 15 μg/plate a toxic effect of the test substance on the bacteria could be observed.
Vehicle controls validity:
not valid
Untreated negative controls validity:
not examined
Positive controls validity:
not valid
Additional information on results:
Experiment 1: it was assumed that the saturated solution has a concentration of 550 mg/L. This corresponds to the maximum solubility determined by the laboratory. A saturated solution was prepared, which was diluted appropriately after filtration.
Experiment 2: a saturated solution was prepared, which was treated with heat and ultrasound and then filtered. The filtrate had a content of 618 mg/L. This value is above the value determined in the solubility test, which is attributable to the application of ultrasound and heat during production. From this saturated solution, the concentration used for the test was prepared by dilution.

EXPERIMENTS
The test substance showed no mutagenic effect in the test. All induction rates were below 2.0.

The controls used to verify the genotype of the S. typhimurium strains fulfilled all criteria.
The mutations caused by the positive controls were lower than stated by Prof. Ames. However, an increased mutant number compared to the spontaneous revertants could be proven beyond doubt with the exception of strains 97a and 102.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
When tested for toxicity, at the maximum dose of 15 μg/plate a toxic effect of the test substance on the bacteria could be observed. In the second determination with 5.5 μg/plate, no toxic effect occurred.
Conclusions:
The test substance showed no mutagenic effect in the test. All induction rates were below 2.0. When tested for toxicity, at the maximum dose of 15 μg/plate a toxic effect of the test substance on the bacteria could be observed. In the second determination with 5.5 μg/plate, no toxic effect occurred.
Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2002-09-25 to 2002-10-18
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
significant methodological deficiencies
Remarks:
Deviations from the OECD 471 (1997): spontaneous revertants counts were not for all strains within historical controls given by the laboratory; historical controls for the spontaneous revertants were only given for cultures without S9 mix; cytotoxicity was only determined without S9 mix and for the highest concentration tested; cytotoxicity was seperately tested and not within the plates used for determining mutagenicity; determination of cytotoxicity was not plausible; third experiment used only three concentration instead of five concentration; positive control with metabolic activation was only included for one strain (TA98); historical data for the positive control are missing
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1997-07-21
Deviations:
yes
Remarks:
please refer to the field "Rationale for reliability incl. deficiencies" above
GLP compliance:
yes (incl. QA statement)
Remarks:
inspection of laboratory: 1999-02-09
Type of assay:
bacterial reverse mutation assay
Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: test material was kept in a closed polyethylene vessel in the dark in a refrigerator
Target gene:
TA97a: hisD6610
TA98: hisD3052
TA100 and TA1535: hisG46
TA102: hisG428
Species / strain / cell type:
S. typhimurium, other: TA1535, TA97a, TA98, TA100, and TA102
Metabolic activation:
with and without
Metabolic activation system:
S9-mix (containing approx. 4 % S9; 2.0 mL): sodium-ortho-phosphate buffer (25.0 mL; pH 7.4); NADP (2 mL); glucose-6-phosphate (0.25 mL); saline solution (1.0 mL); water, dest. steril: 19.75 mL
Test concentrations with justification for top dose:
Experiment 1: 0.5, 1.6, 5.3, 15.8, and 52.8 µg/plate (with and without metabolic activation)
Experiment 2: 5, 10, and 20 µg/plate (with and without metabolic activation)
Experiment 3: 2.5, 5, and 10 µg/plate (with and without metabolic activation)
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: demineralized water
The test substance was dissolved in demineralised water. This was done in the first experiment by taking an excess amount of the test item and treating it with ultrasound, heat, and shaking followed by subsequent filtration of the resulting solution. In the second and third experiments, the appropriate amount of the substance was determined by weighing and then dissolved in demineralized water.
The resulting stock solutions were sterile filtered and diluted to produce the concentrations to be tested.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
Remarks:
demineralized water
True negative controls:
no
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
sodium azide
benzo(a)pyrene
cumene hydroperoxide
other: 4-Nitro-1,2-phenylendiamin (without metabolic activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION:
Experiment 1: in agar (plate incorporation)
Experiment 2 & 3: preincubation

EXPERIMENTAL PERFORMANCE
Experiment 1:
- 0.1 mL of the test substance solution was pipetted into a sterile tube.
- then, the tube was filled up with 2 mL of top agar, followed by adding 0.1 mL of bacteria suspension and 0.5 mL of phosphate buffer (testing without S9) or 0.5 mL of S9 mix (testing with S9).
- after short panning, tube content was poured onto a minimal glucose plate and the mixture was evenly spread with a Drigalski spatula.
- the plate was closed and covered with brown paper (for protection against UV radiation) and left on a flat surface until the agar solidifies
- after solidification, the plate was turned over and placed into a dark, 37 °C hot incubator.
- incubation lasted 48 hours
- number of revertants/plate were counted

Experiment 2 & 3:
- 0.1 mL of the test substance solution was pipetted into a sterile tube followed by 0.1 mL of bacteria suspension and 0.5 mL of phosphate buffer (testing without S9) or 0.5 mL S9 mix (testing with S9).
- this mixture were preincubated for 20 minutes at 37 ° C in a incubator. During the incubation the tubes were aerated by shaking.
- then 2 mL of top agar were added and the content of the tubes was poured onto a minimal glucose plate after a short panning and the mixture was evenly spread with a Drigalski spatula.
- the plate was closed and covered with brown paper (for protection against UV radiation) and left on a flat surface until the agar solidifies
- after solidification, the plate was turned over and placed in a dark, 37 ° C hot incubator.
- incubation lasted 48 hours
- number of revertants/plate were counted

Validation of the genotype, determination of titer, and control of sterility were also carried out.

NUMBER OF REPLICATIONS: quadruplicate

DETERMINATION OF CYTOTOXICITY
Each strain was tested with the test substance at its maximum concentration (experiment 1: 52.8 µg/plate; experiment 2: 20 µg/plate; experiment 3: 10 µg/plate) without metabolic activation.
Rationale for test conditions:
not specified
Evaluation criteria:
A test substance is considered to be mutagenic, if in at least one of the strains used, with or without S9 mix, a twofold increase in mutant numbers compared to the negative control is induced (induction rate I ≥ 2) or shows a concentration-response relationship.
Statistics:
The evaluation of the data was carried out by using a spreadsheet program (Microsoft Excel®). The induction rates were tabulated against the dilution of the test substance.
Key result
Species / strain:
S. typhimurium, other: TA1535, TA97a, TA98, TA100, and TA102
Metabolic activation:
with and without
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
xperiment 1 (52.8 µg/plate; without S9 mix): cytotoxicity was observed for TA98, TA100, and TA102.
Vehicle controls validity:
not valid
Untreated negative controls validity:
not examined
Positive controls validity:
not valid
Additional information on results:
NOTE: Due to the non-compliance with the validity criteria (titre controls too low, positive controls partly not recognized as mutagenic) in the second experiment, this was considered as not valid and was repeated.

Experiment 1: a slight increase in revertants was observed only for the highest test substance concentration (52.8 µg/plate) for strain TA97a without metabolic activation (induction rate 2.9).
Experiment 2 (not valid experiment, see explanation above): the revertants were increased in TA97a with metabolic activation (10 µg/plate; induction rate 2.5), TA98 without metabolic activation (10µg/plate; induction rate 3.4) and TA1535 with metabolic activation (5 µg/plate; induction rate 13.27); a dose-response relationship was not observed.
Experiment 3: no mutagenic effects were observed up to the highest dose tested (10 µg/plate)

ADDITIONAL INFORMATION ON CYTOTOXICITY:
Experiment 1 (52.8 µg/plate; without S9 mix): cytotoxicity was observed for TA98, TA100, and TA102.
Experiment 2 (20 µg/plate; without S9 mix): cytotoxicity was observed for all strains. Due to the non-compliance with the validity criteria (titre controls too low, positive controls partly not recognized as mutagenic) in the second experiment, this was considered as not valid and repeated.
Experiment 3 (10 µg/plate; without S9 mix): no cytotoxicity was observed

The controls used to verify the genotype of the S. typhimurium strains fulfilled all criteria. For the positive control, an increased mutant number compared to the spontaneous revertants could be proven beyond doubt.

Please also refer to the field "Attached background material" below
Remarks on result:
not determinable because of methodological limitations
Conclusions:
In the one experiment, a slight increase in revertants was observed only for the highest test substance concentration (52.8 µg/plate) for strain TA97a without metabolic activation (induction rate 2.9) and cytotoxicity was observed for TA98, TA100, and TA102 at a concentration of 52.8 µg/plate (without S9 mix). In another experiment no mutagenic effects were observed up to the highest dose tested (10 µg/plate) and cytotoxicity was not oberved at a concentration of 10 µg/plate (without S9 mix).


Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2003-01-27 to 2003-01-31
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
significant methodological deficiencies
Remarks:
Deviations from the OECD 471 (1997): spontaneous revertants counts were not for all strains within historical controls given by the laboratory; historical controls for the spontaneous revertants were only given for cultures without S9 mix; historical data for the positive control are missing
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1997-07-21
Deviations:
yes
Remarks:
Please refer to the field "Rationale for reliability incl. deficiencies" above
GLP compliance:
yes (incl. QA statement)
Remarks:
inspection of laboratory: 1999-02-09
Type of assay:
bacterial reverse mutation assay
Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: test material was kept in a closed polyethylene vessel in the dark in a refrigerator
Target gene:
TA97a: hisD6610
TA98: hisD3052
TA100 and TA1535: hisG46
TA102: hisG428
Species / strain / cell type:
S. typhimurium, other: TA1535, TA97a, TA98, TA100, and TA102
Metabolic activation:
with and without
Metabolic activation system:
S9 mix
Test concentrations with justification for top dose:
0.5, 1.5, 5.1, 15.4, and 51.4 µg/plate (with and without metabolic activation)
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: demineralized water
The test article was dissolved in demineralized water. This was done by weighing a surplus into a vessel followed by shaking for 24 hours and subsequent sterile filtration of the resulting solution. Before filtration, flocculations could be observed. The concentrations to be tested were prepared by dilution.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
Remarks:
demineralized water
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
benzo(a)pyrene
cumene hydroperoxide
other: 4-Nitro-1,2-phenylendiamin (without metabolic activation) & 2- aminoanthrcene (with metabolic activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION: preincubation

EXPERIMENTAL PERFORMANCE
- 0.1 mL of the test substance solution was pipetted into a sterile tube followed by 0.1 mL of bacteria suspension and 0.5 mL of phosphate buffer (testing without S9) or 0.5 mL S9 mix (testing with S9).
- this mixture were preincubated for 20 minutes at 37 ° C in a incubator. During the incubation the tubes were aerated by shaking.
- then 2 mL of top agar were added and the content of the tubes was poured onto a minimal glucose plate after a short panning and the mixture was evenly spread with a Drigalski spatula.
- the plate was closed and covered with brown paper (for protection against UV radiation) and left on a flat surface until the agar solidifies
- after solidification, the plate was turned over and placed in a dark, 37 ° C hot incubator.
- incubation lasted 48 hours
- number of revertants/plate were counted

Validation of the genotype, determination of titer, and control of sterility were also carried out.

NUMBER OF REPLICATIONS: quadruplicate

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth
Rationale for test conditions:
not specified
Evaluation criteria:
A test substance is considered to be mutagenic, if in at least one of the strains used, with or without S9 mix, a twofold increase in mutant numbers compared to the negative control is induced (induction rate I ≥ 2) or shows a concentration-response relationship.
Statistics:
The evaluation of the data was carried out by using a spreadsheet program (Microsoft Excel®). The induction rates were tabulated against the dilution of the test substance.
Key result
Species / strain:
S. typhimurium, other: TA1535, TA97a, TA98, TA100, and TA102
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
Cytotoxicity was observed for TA97a at the concentration of 51.4 µg/plate (without metabolic activation).
Vehicle controls validity:
not valid
Untreated negative controls validity:
not examined
Positive controls validity:
not valid
Additional information on results:
The test article was dissolved in demineralized water. A stock solution of the maximum soluble amount was prepared. This showed clear precipitations before the sterile filtration. Due to the decision to use the test article sterile, no precipitation in the final mixture could be observed. The analytically determined concentration of the stock solution of 514 mg / L, however, agrees well with the determined maximum water solubility of 551 mg/L, so that it can be assumed that the maximum dose corresponds to the maximum soluble amount of the test object.

EXPERIMENT
In the experiment no significant increase in revertant numbers could be observed in any of the tested strains with and without metabolic activation at any tested concentration of the test article. No dose-response relationship could be determined.

Validation of the genotype, determination of titer, and control of sterility were also carried out. In the titer determination, the spontaneous revertant and the positive controls, the expected revertant numbers were found, which were within the usual history values for the test laboratory.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
Cytotoxicity was observed for TA97a at the concentration of 51.4 µg/plate (without metabolic activation).

Please also refer to the field "Attached background material" below
Conclusions:
In the experiment no significant increase in revertant numbers could be observed in any of the tested strains with and without metabolic activation at any tested concentration of the test article. No dose-response relationship could be determined. Cytotoxicity was observed for TA97a at the concentration of 51.4 µg/plate (without metabolic activation). If the results of this test are compared with the data from the first experiments (please refer to Section 7.6.1 Genetic toxicity in vitro: w_Paulus_2002_bacterial reverse mutation assay (repetition)) , it can be assumed that the test object shows no mutagenic effect either with or without metabolic activation. Therefore, the test article can be classified as not mutagenic under the test conditions.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Genetic toxicity in vitro

Based on a weight of evidence approach, the substance was not observed to be mutagenic in three bacterial reverse mutation assay (OECD 471).

Justification for classification or non-classification

Genetic toxicity in vitro

The test substance should be considered void of genotoxicity based on weight of evidence approach using three bacterial reverse mutation assay (OECD 471). Thus, the test substance has no mutagenic potenital and does not require classification according to Regulation (EC) No 1272/2008 and subsequent adaptations.