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Genetic toxicity: in vitro

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Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
August 06, 2013 to September 19, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study performed in accordance with OECD test guidelines in compliance with GLP.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2014
Report Date:
2014

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
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
other: Colorless and transparent liquid
Details on test material:
Name of new chemical (IUPAC nomenclature): Ethane, 1-ethoxy-2-(2-methoxyethoxy)-
Other name: DEGMEE
Structural formula or rational formula (or outline of manufacturing method, in case both are unknown): C2H5O(CH2CH2O)2CH3
Purity of new chemical: 99.98%
Lot No. of new tested chemical tested: 20130625
Name and concentration of impurities: Impurities: 0.02%; BHT: 0.004%; Unknown: 0.016%
CAS No.: 1002-67-1
Vapor pressure: 0.68 mmHg (20°C)
Molecular weight: 148.20
Partition coefficient
Melting point: -71.7°C
Appearance at ambient temperature: Colorless and transparent liquid
Boiling point: 179°C
Stability: By the normal handing, it is chemically stable for heat, light, a shock.
Solubility in several solvents: Water: Soluble (dissolved at 50 mg/mL); DMSO dissolved at 50 mg/mL; Acetone dissolved at 100 mg/mL

Method

Target gene:
histidine and tryptophan.
Species / strain
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
S9-mix
Test concentrations with justification for top dose:
Preliminary test: 1.22, 4.88, 19.5, 78.1, 313, 1250, 5000 μg/plate (With and without S9 mix)Main test I and main test II: 313, 625, 1250, 2500, 5000 μg/plate (Without S9 mix); 313, 625, 1250, 2500, 5000 μg/plate (With S9 mix)
Vehicle / solvent:
Vehicle not used in the study
Controls
Untreated negative controls:
yes
Remarks:
sterilized distilled water (DW)
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
sodium azide
other: 2-(2-Furyl)-3-( 5-nitro-2-furyl)acrylamide (AF-2); 2-Aminoanthracene (2-AA)
Details on test system and experimental conditions:
Measurement of the number of cells in bacterial suspensionAfter pre-culture, bacterial density of each strain was measured by a digital photometer (TAITEC Co., Ltd. Mini photo 518R), and then the bacterial suspension for counting the number of cells was prepared by the stepwise dilution method. The suspension was overlaid to a minimal glucose agar plate and incubated at 37°C for 48 hours. The number of cells was calculated by counting the number of colonies on the plate. The bacterial suspension for the reverse mutation test was stored at room temperature. The number of cells of each bacterial suspension is shown in table form (see Any other information).MediaPreparation of liquid growth medium:Oxoid Nutrient Broth No.2 (Oxoid Ltd., Lot No.941971) 2.5 g was dissolved in 100 mL of purified water. The medium was autoclaved for 15 minutes at 121 °C and stored in a cold storage.Preparation of top agarPreparation of soft agarBacto-agar (Becton Dickinson and Company, Lot No.2299369) 0.6 g and sodium chloride (Wako Pure Chemical Industries, Ltd.) 0.5 g were added to 100 mL of purified water. This mixture was autoclaved for 15 minutes at 121 °C and then was stored at 45°C until use.Preparation of top agarEach of the following each amino acid solution was added to the soft agar at a volume ratio of 1 to 10 just before use. The top agar was kept at 45°C until use.Salmonella typhimurium: 0.5 mmol/L D-biotin and 0.5 mmol/L L-histidine solution mixtureEscherichia coli: 0.5 mmol!L L-tryptophan solutionS9 mixS9Manufacturer: Kikkoman Biochemifa CompanyLot No.: RAA20130405Preparation date: April 05, 2013S9 preparationThe S9 was prepared from the livers of 7-week old male Sprague-Dawley rats (body weight: 213 to 246 g) treated with phenobarbital (PB, 4 times at 24-hour intervals at i.p. doses of 30, 60, 60 and 60 mg/kg, respectively) and 5, 6-benzoflavone (once at a single i.p. dose of 80 mg/kg on the same day of the third PB injection).Protein content: 25.96mg/mLStorage conditions: Below -80°C [Sanyo Ultralow freezer; :MDF-192]Expiration date: October 05, 2013 (6 months after preparation)Cofactor mixName: Cofactor-IManufacturer: Oriental Yeast Co., Ltd.Lot No.: 999301Cofactor preparation: Cofactor-I was dissolved in 9 mL of sterile purified water and filtrated with a membrane filter (pore size: 0.45 μm) to give a cofactor mix. The cofactor mix was freshly prepared just prior to use.S9 mixOne milliliter of S9 was added to 9 mL of the cofactor mix to give the proper ratio for the S9 mix. The S9 mix was freshly prepared just prior to use in each test and was kept in an ice bath until use. The ingredients and their contents per milliliter of the S9 mix preparation were as follows (reported in table form see Any other information).Preparation of the test substance and positive control solutionsPreparation of the test substance solutionsPreparation(1) The test substance was weighed and dissolved in DW with vortex mixing to make a 50 mg/mL solution.(2) A portion of this solution was diluted stepwise with DW to make the test substance solutions of each concentration.(3) All procedures, including those for weighing the test substance, dilution, dispensation and treatment of the dispersion, were performed under a yellow light at room temperature.Storage period and temperatureThe storage period and temperature after preparation of the test substance solutions to the time of use were as follows;Preliminary test: 2 hours and 18 minutes at room temperature (24 °C)Main test 1: 1 hour and 37 minutes at room temperature (24°C)Main test II: 1 hour and 23 minutes at room temperature (24 °C)Preparation of positive control solutionsPreparationPositive control solutions were prepared by the following method;(1) NaN3 was dissolved in sterilized distilled water (Wako Pure Chemical Industries, Ltd.) and AF-2, 9-AA and 2-AA were dissolved in DMSO (Dojindo Laboratories).(2) The above preparations were diluted with each solvent for preparing stock solutions.Usage of the positive control solutionsThe positive control solutions were prepared and stored as stock solutions, the stock solutions of positive control were thawed before use and used for the study. 2-AA stock solution was diluted more with DMSO at tested concentration. The remainders of thawed solutions were not reused.Storage of the positive control solutions: Divided into freezing tubes (1.0 mL) and frozenStorage conditions: Below -20°C [Pharmaceutical refrigerator with freezer; MPR-414FS] (AF-2, NaN3 and 9-AA); Below-80°C [Sanyo Ultralow freezer; MDF-192] (2-AA)Reverse mutation testSelection of the test methodThis study was performed using the pre-incubation method with and without S9 mix.Pre-incubation method(1) For each treatment, 0.1 mL of the test substance solution, negative (solvent) control or positive control solution was added into a sterilized test tube with aluminum cap.(2) For assays without S9 mix, 0.5 mL of 0.1 mol/L sodium phosphate buffer (pH 7.4) was mixed and 0.1 mL of the bacterial suspension was added to this mixture.(3) For assays with S9 mix, 0.5 mL of S9 mix was mixed and 0.1 mL of the bacterial suspension was added to this mixture.(4) The mixture was incubated with gentle shaking (Shaking frequency: 120 times/minute) for 20 minutes at 37°C (pre-incubation).(5) After pre-incubation, 2 mL of the molten top agar was added to this mixture and then poured onto a minimal glucose agar plate.(6) After the overlaid agar had solidified, the plates were incubated for 48 hours at 37°C.Sterility testIn the preliminary and two main tests, bacterial contamination was examined using one plate for each of the highest dose of the test substance solution, S9 mix, and the 0.1 mol/L sodium phosphate buffer.(1) 0.1 mL of the highest dose of the test substance solution or 0.5 mL of the S9 mix or the 0.1 mol/L sodium phosphate buffer was mixed with 2 mL of the molten top agar.(2) The mixture was poured onto a minimal glucose agar plate.(3) After the overlaid agar had solidified, the plates were incubated for 48 hours at 37°C and then checked for bacterial contamination macroscopically.ObservationPrecipitation: Precipitation was judged by observation of the plate surface macroscopically.Microbial growth inhibition: Background lawn of the bacterial cells that have amino-acid requirement was observed by a stereoscopic microscope (Nikon, SMZ-10), and microbial growth inhibition was judged by the relationship between the test substance treated plates and the negative (solvent) control plate.Measurement of colony numberRevertant colonies were measured using an automatic colony counter (System Science Co., Ltd., CA-11D) or manual counting. Revertant colonies in positive control treatment groups, in TA100 of test substance treatment groups without precipitation, and in the test substance treatment groups in which many revertant colonies were observed were measured using an automatic colony counter and the others measured by manual counting. Correction of the measuring area was employed using instrumental analysis.Number of platePreliminary test: 1 plate/dose (2 plates/dose for the negative (solvent) and positive controls)Main test I: 3 plates/doseMain test II: 3 plates/doseExpression of dataIn the preliminary test, the mean of revertant colonies were calculated for the negative (solvent) control and the positive control.In the main test, the mean and the standard deviation of revertant colonies were calculated for the negative (solvent) control, the positive control and the test substance treatment groups. The mean and the standard deviation were expressed by rounding to the first decimal place.
Evaluation criteria:
The main tests were accepted as valid if all the following criteria were satisfied. The preliminary test was accepted as valid if the data by which doses were set in the main tests was provided.(1) The negative (solvent) control values (mean) and the positive control values (mean) are within the proper ranges calculated based on the historical data at our laboratory.(2) The positive control values (mean) show clear positive responses in the respective tester strains, as evidenced by the number of revertant colonies being greater than 2-fold of the respective negative (solvent) control value (mean).(3) There are more than 4 doses showing no microbial growth inhibition and more than 5 doses applicable to the evaluation.(4) The result of the sterility test indicates that there is no bacterial contamination.(5) There are no plates that became invalid for measurement due to contamination or other unexpected situations.Test substance was judged to have mutagenicity (positive) when the test substance induced a dose-dependent increase in the number of the revertant colonies (mean) to a level equal to or greater than 2-fold of the negative (solvent) control value (mean value) in any one of the tester strains with or without S9 mix, and when the dose-dependent increase was reproducible. Other results were judged to be negative. Mutation activities (number of revertant colonies/mg.) were not calculated because the test substance was judged to be negative.
Statistics:
No statistical analysis was performed with the test results in this study.

Results and discussion

Test results
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
not examined
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Preliminary testNumber of revertant colonies: The number of revertant colonies in the test substance-treated groups was less than twice that in the corresponding negative (solvent) control in any tester strains with or without S9 mix.Microbial growth inhibition: Microbial growth inhibition was not observed in any tester strains with or without S9 mix.Precipitation: Precipitation of the test substance was not observed in any tester strains with or without S9 mix.Main test INumber of revertant colonies: The number of revertant colonies in the test substance-treated groups was less than twice that in the corresponding negative (solvent) control in any tester strains with or without S9 mix.Microbial growth inhibition: Microbial growth inhibition was not observed in any tester strains with or without S9 mix.Precipitation: Precipitation of the test substance was not observed in any tester strains with or without S9 mix.Main test IINumber of revertant colonies: The number of revertant colonies in the test substance-treated groups was less than twice that in the corresponding negative (solvent) control in any tester strains with or without S9 mix.Microbial growth inhibition: Microbial growth inhibition was not observed in any tester strains with or without S9 mix.Precipitation: Precipitation of the test substance was not observed in any tester strains with or without S9 mix.Sterility testBacterial or fungous contamination was not observed in plates of the highest dose of the test substance solution, S9 mix or the 0.1 mol/L sodium phosphate buffer in the preliminary test and two main tests.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Any other information on results incl. tables

Results of the preliminary test

Test substance: DEGMEE

Testing periods

From August 06, 2013 to August 09, 2013

Metabolic activation system

Test substance concentration (μg/plate)

Number of revertants (number of colonies/plate)

Base-pair change type

Frameshift type

TA100

TA1535

WP2uvrA

TA98

TA1537

S9 mix (-)

Solvent control

142

134

 

(138)

11

10

 

(11)

39

40

 

(40)

22

20

 

(21)

13

9

 

(11)

1.22

138

 

12

 

42

 

25

 

10

 

4.88

144

 

9

 

39

 

24

 

8

 

19.5

139

 

12

 

33

 

23

 

8

 

78.1

138

 

9

 

42

 

23

 

10

 

313

141

 

9

 

43

 

21

 

13

 

1250

124

 

10

 

36

 

20

 

13

 

5000

141

 

8

 

42

 

22

 

13

 

S9 mix (+)

Solvent control

132

139

 

(136)

11

10

 

(11)

35

31

 

(33)

20

23

 

(22)

12

9

 

(11)

1.22

136

 

11

 

33

 

22

 

12

 

4.88

132

 

8

 

33

 

23

 

12

 

19.5

146

 

9

 

30

 

30

 

12

 

78.1

140

 

8

 

42

 

28

 

11

 

313

138

 

11

 

39

 

26

 

8

 

1250

140

 

10

 

39

 

31

 

12

 

5000

137

 

10

 

31

 

29

 

10

 

Positive control not requiring S9 mix

Name and concentration (μg/plate)

AF-2

0.01

NaN3

0.5

AF-2

0.01

AF-2

0.1

9-AA

80

Number of revertant colonies per plate

707

714

 

(711)

419

385

 

(402)

204

185

 

(195)

574

602

 

(588)

346

379

 

(363)

Positive control requiring S9 mix

Name and concentration (μg/plate)

2-AA

1

2-AA

2

2-AA

10

2-AA

0.5

2-AA

2

Number of revertant colonies per plate

787

787

 

(787)

355

275

 

(315)

1141

1182

 

(1162)

370

380

 

(375)

153

136

 

(145)

AF-2: 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide; NaN3: Sodium azide; 9-AA: 9-aminoacridine hydrochloride monohydrate; 2-AA: 2-aminoanthracene

[Note]

1. Fill average number of colonies in each concentration in the “( )”.

2. “Number of revertants” – Fill in the observed value and average value in order beginning with low concentration of the test substance

 

Results of the main test I

Test substance: DEGMEE

Testing periods

 

From August 20, 2013 to August 23, 2013

Metabolic activation system

Test substance concentration (μg/plate)

Number of revertants (number of colonies/plate)

Base-pair change type

Frameshift type

TA100

TA1535

WP2uvrA

TA98

TA1537

S9 mix (-)

Solvent control

137

142

129

[136 ± 7]

12

9

10

[10 ± 2]

35

36

33

[35 ± 2]

21

24

20

[22 ± 2]

12

13

12

[12 ± 1]

313

135

139

134

[136 ± 3]

9

7

8

[8 ± 1]

36

38

35

[36 ± 2]

23

23

25

[24 ± 1]

11

13

11

[12 ± 1]

625

142

123

137

[134 ± 10]

10

8

7

[8 ± 2]

30

30

39

[33 ± 5]

24

20

23

[22 ± 2]

11

9

13

[11 ± 2]

1250

135

138

129

[134 ± 5]

10

12

11

[11 ± 1]

33

31

39

[34 ± 4]

24

21

25

[23 ± 2]

11

13

10

[11 ± 2]

2500

122

122

127

[124 ± 3]

13

12

12

[12 ± 1]

24

36

38

[36 ± 2]

20

17

17

[18 ± 2]

12

12

10

[11 ± 1]

5000

124

113

114

[117 ± 6]

11

12

11

{11 ± 1]

30

22

30

[31 ± 2]

20

18

20

[19 ± 1]

13

12

12

[12 ± 1]

S9 mix (+)

Solvent control

135

139

145

[140 ± 5]

11

8

8

[9 ± 2]

31

36

33

[33 ± 3]

29

30

30

[30 ± 1]

12

13

12

[12 ± 1]

313

141

146

146

[144 ± 3]

8

10

8

[9 ± 1]

34

28

27

[30 ± 4]

28

32

26

[29 ± 3]

12

11

10

[11 ± 1]

625

137

138

138

[138 ± 1]

8

810

[9 ± 1]

29

27

27

[28 ± 1]

29

25

25

[26 ± 2]

11

10

7

[9 ± 2]

1250

149

139

149

[146 ± 6]

10

8

11

[9 ± 2]

32

26

31

[30 ± 3]

27

25

25

[26 ± 1]

10

9

10

[10 ± 1]

2500

146

151

152

[150 ± 3]

13

8

10

[10 ± 2]

37

32

37

[35 ± 3]

29

27

23

[26 ± 3]

11

9

10

[10 ± 1]

5000

145

139

143

[142 ± 3]

8

11

11

[10 ± 2]

28

30

30

[29 ± 1]

29

23

28

[27 ± 3]

7

10

11

[9 ± 2]

Positive control not requiring S9 mix

Name and concentration (μg/plate)

AF-2

0.01

NaN3

0.5

AF-2

0.01

AF-2

0.1

9-AA

80

Number of revertant colonies per plate

850

90

859

[870 ± 27]

474

456

415

[448 ± 30]

242

231

242

[238 ± 6]

659

689

667

[672 ± 16]

564

464

496

[508 ± 51]

Positive control requiring S9 mix

Name and concentration (μg/plate)

2-AA

1

2-AA

2

2-AA

10

2-AA

0.5

2-AA

2

Number of revertant colonies per plate

857

884

849

[863 ± 18]

280

294

315

[296 ± 18]

976

916

1006

[966 ± 46]

416

415

484

[438 ± 40]

180

171

165

[172 ± 8]

AF-2: 2-(furyl)-3-(5-nitro-2-furyl)acrylaminde; NaN3: sodium azide; 9-AA: 9-aminoacridine hydrochloride monohydrate; 2-AA: 2-aminoanthracene

[Note]

1. The average and standard deviation value of colonies for each concentration is in the “[ ]”.

2. “Number of revertants” – Fill in the observed value and average value in order beginning with low concentrations of the test substance.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):negative with and without metabolic activationIt was concluded that DEGMEE was not mutagenic under the conditions employed in this study.
Executive summary:

Mutagenicity of the test substance, DEGMEE, was assessed in the bacterial reverse mutation test using five strains, Salmonella typhimurium TA100, TA1535, TA98 and TA1537, and Escherichia coli WP2uvrA. The test was conducted by the pre-incubation method with and without S9 mix.

Study performed to OECD Guidelines for the Testing of Chemicals (No. 471, 1997)

 

A preliminary test was performed at 5000 μg/plate as the maximum dose using 7 doses with a common ratio of 4. As the results, the number of revertant colonies treated with the test substance was less than twice that treated with the negative control (solvent) in any tester strains with or without S9 mix.

Microbial growth inhibition and precipitation of the test substance were not observed in any tester strains with or without S9 mix.

 

The main test I was performed at 5000 μg/plate as the maximum dose using 5 doses with a common ratio of 2 based on the results of the preliminary test. As the results, the number of revertant colonies treated with the test substance was less than twice that treated with the negative control (solvent) in any tester strains with or without S9 mix.

Microbial growth inhibition and precipitation of the test substance were not observed in any tester strains with or without S9 mix.

 

The main test II was performed at 5000 μg/plate as the maximum dose using the same doses as the main test I. As the results, the number of revertant colonies treated with the test substance was less than twice that treated with the negative control (solvent) in any tester strains with or without S9 mix.

Microbial growth inhibition and precipitation of the test substance were not observed in any tester strains with or without S9 mix.

From the results described above, it was concluded that DEGMEE was not mutagenic under the conditions employed in this study.

 

In the main test I, the number of revertant colonies induced by the test substance was less the twice of that of the corresponding negative control value for any tester strains with or without S9 mix. The same result was obtained also in the main test II, and the reproducibility of the test results was confirmed. Furthermore, both tests were performed accurately because the acceptable criteria were satisfied.

 

From the results described above, it was concluded that DEGMEE was not mutagenic under the conditions employed in this study.