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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
Study period:
August 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of assay:
bacterial reverse mutation assay

Test material

Constituent 1
Reference substance name:
Pentanol, branched and linear
EC Number:
305-536-1
EC Name:
Pentanol, branched and linear
Cas Number:
94624-12-1
Molecular formula:
C5 H12 O
IUPAC Name:
Reaction mass of 2-methylbutan-1-ol and pentan-1-ol

Method

Species / strain
Species / strain / cell type:
E. coli WP2 uvr A
Metabolic activation:
with and without
Metabolic activation system:
The S9 fraction was prepared according to Ames et al. at BASF SE in an AAALAC approved laboratory in accordance with the German Animal Welfare Act and the effective European Council Directive. At least 5 male Wistar rats [Crl:WI(Han)] (200 - 300 g; Charles River Laboratories Germany GmbH) received 80 mg/kg b.w. phenobarbital i.p. and β-naphthoflavone orally (both supplied by Sigma-Aldrich, 82024 Taufkirchen, Germany) each on three consecutive days. During this time, the animals were housed in polycarbonate cages: central air conditioning with a fixed range of temperature of 20 - 24°C and a fixed relative humidity of 30 - 70%. The day/night rhythm was 12 hours: light from 6 am to 6 pm and darkness from 6 pm to 6 am. Standardized pelleted feed and drinking water from bottles were available ad libitum. 24 hours after the last administration, the rats were sacrificed, and the livers were prepared using sterile solvents and glassware at a temperature of +4°C. The livers were weighed and washed in a weight-equivalent volume of a 150 mM KCl solution and homogenized in three volumes of KCl solution. After centrifugation of the homogenate at 9000 x g for 10 minutes at +4°C, 5 mL portions of the supernatant (S9 fraction) were stored at -70°C to -80°C.
The S9 mix was prepared freshly prior to each experiment. For this purpose, a sufficient amount of S9 fraction was thawed at room temperature and 1 part of S9 fraction is mixed with 9 parts of S9 supplement (cofactors). This mixture of both components (S9 mix) was kept on ice until used. The concentrations of the cofactors in the S9 mix were:
MgCl2 8 mM
KCl 33 mM
glucose-6-phosphate 5 mM
NADP 4 mM
phosphate buffer (pH 7.4) 15 mM
The phosphate buffer (6) is prepared by mixing a Na2HPO4 solution with a NaH2PO4 solution in a ratio of about 4:1. To demonstrate the efficacy of the S9 mix in this assay, the S9 batch was characterized with benzo(a)pyrene.
Test concentrations with justification for top dose:
In agreement with the recommendations of current guidelines 5 mg/plate or 5 μL/plate were generally selected as maximum test dose at least in the 1st Experiment. However, this maximum dose was tested even in the case of relatively insoluble test compounds to detect possible mutagenic impurities. Furthermore, doses > 5 mg/plate or > 5 μL/plate might also be tested in repeat experiments for further clarification/substantiation.
Vehicle / solvent:
Due to the insolubility of the test substance in water, DMSO was used as vehicle, which had been demonstrated to be suitable in bacterial reverse mutation tests and for which historical control data are available.
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
other: 2-aminoanthracene (2-AA)
Details on test system and experimental conditions:
The experimental procedure of the standard plate test (plate incorporation method) is based on the method of Ames et al..
• Escherichia coli
Test tubes containing 2-mL portions of soft agar (overlay agar), which consists of 100 mL agar (0.8% [w/v] agar + 0.6% [w/v] NaCl) and 10 mL amino acid solution (minimal amino acid solution for the determination of mutants: 0.5 mM tryptophan) were kept in a water bath at about 42 - 45°C, and the remaining components were added in the following order:
0.1 mL test solution or vehicle (negative control)
0.1 mL fresh bacterial culture
0.5 mL S9 mix (with metabolic activation)
or
0.5 mL phosphate buffer (without metabolic activation)
After mixing, the samples were be poured onto Minimal glucose agar plates (Moltox Molecular Toxicology, Inc.; Boone, NC 28607; USA) within approx. 30 seconds. After incubation at 37°C for 48 – 72 hours in the dark, the bacterial colonies (trp+ revertants) were counted. The colonies were counted using the Sorcerer Image Analysis System with the software program Ames Study Manager (Perceptive Instruments Ltd., Haverhill, UK). Colonies were counted manually, if precipitation of the test substance hinders the counting using the Image Analysis System.

Preincubation Test
The experimental procedure was based on the method described by Yahagi et al. and Matsushima et al.. 0.1 mL test solution or vehicle, 0.1 mL bacterial suspension and 0.5 mL S9 mix (with metabolic activation) or phosphate buffer (without metabolic activation) were incubated at 37°C for the duration of about 20 minutes using a shaker. Subsequently, 2 mL of soft agar was added and, after mixing, the samples were poured onto the agar plates within approx. 30 seconds. After incubation at 37°C for 48 – 72 hours in the dark, the bacterial colonies were counted. The colonies were counted using the Sorcerer Image Analysis System with the software program Ames Study Manager (Perseptive Instruments Ltd., Haverhill, UK). Colonies were counted manually, if precipitation of the test substance hindered the counting using the Image Analysis System.

1st Experiment
Strain: E. coli WP2 uvrA
Doses: 0; 33; 100; 333; 1000; 2500 and 5000 μg/plate
Type of test: Standard plate test with and without S9 mix
Number of plates: 3 test plates per dose or per control
2nd Experiment
Strain: E. coli WP2 uvrA
Doses: 0; 33; 100; 333; 1000; 2500 and 5000 μg/plate
Type of test: Preincubation test with and without S9 mix
Number of plates: 3 test plates per dose or per control
Reason: No mutagenicity was observed in the standard plate test.

Mutagenicity
Individual plate counts, the mean number of revertant colonies per plate and the standard deviations were given for all dose groups as well as for the positive and negative (vehicle) controls in all experiments. In general, six doses of the test substance were tested with a maximum of 5 mg/plate, and triplicate plating was used for all test groups at least in the 1st Experiment. Dose selection and evaluation as well as the number of plates used in repeat studies or further experiments were based on the findings of the 1st Experiment.

Toxicity
Toxicity detected by a
• decrease in the number of revertants (factor ≤ 0.6)
• clearing or diminution of the background lawn (= reduced his- or trp- background growth)
was recorded for all test groups both with and without S9 mix in all experiments and indicated in the tables. Single values with a factor ≤ 0.6 were not detected as toxicity in low dose groups.

Solubility
If precipitation of the test material was observed, it would be recorded and indicated in the tables. As long as precipitation did not interfere with the colony scoring, 5 mg/plate was generally selected and analyzed (in cases of nontoxic compounds) as the maximum dose at least in the 1st Experiment even in the case of relatively insoluble test compounds to detect possible mutagenic impurities. Furthermore, doses > 5 mg/plate might also be tested in repeat experiments for further clarification/substantiation.
Rationale for test conditions:
Acceptance criteria
Generally, the experiment was considered valid if the following criteria were met:
• The number of revertant colonies in the negative controls was within the range of the historical negative control data for the tester strain.
• The sterility controls revealed no indication of bacterial contamination.
• The positive control substances both with and without S9 mix induced a distinct increase in the number of revertant colonies within the range of the historical positive control data or above.
• Fresh bacterial culture containing approximately 10^9 cells per mL were used.

Assessment criteria
The test substance was considered positive in this assay if the following criteria were met:
• A dose-related and reproducible increase in the number of revertant colonies, i.e. at least doubling of the spontaneous mutation rate in the tester strain either without S9 mix or after adding a metabolizing system.
A test substance was generally considered non-mutagenic in this test if:
• The number of revertants for the tester strain were within the historical negative control data range under all

Results and discussion

Test results
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
TOXICITY
No bacteriotoxic effect (reduced trp- background growth, decrease in the number of trp+ revertants) was observed in the standard plate and preincubation test up to the highest concentration.
SOLUBILITY
No test substance precipitation was found with and without S9 mix.

Any other information on results incl. tables

The Tables below are presented with the following column order:

Strain, Test group, Dose (µg/plate), Mean revertants per plate, Standard deviation, Factor, Individual revertant colony counts

Standard Plate test

Without metabolic activation


E. coli

DMSO

-

25.3

0.6

-

26, 25, 25

 

Test item

33

22.0

2.6

0.9

20, 21, 25

 

 

100

21.0

3.6

0.8

18, 25, 20

 

 

333

16.7

6.7

0.7

11, 15, 24

 

 

1000

23.0

4.0

0.9

27, 19, 23

 

 

2500

25.0

6.2

1.0

23, 32, 20

 

 

5000

18.0

4.4

0.7

23, 15, 16

 

4-NQO

5

824.3

27.5

32.5

856, 810, 807

With metabolic activation


E. coli

DMSO

-

27.3

1.5

-

27, 29, 26

 

Test item

33

26.0

2.0

1.0

26, 28, 24

 

 

100

25.0

4.4

0.9

28, 20, 27

 

 

333

27.0

5.2

1.0

24, 24, 33

 

 

1000

34.0

7.5

1.2

27, 42, 33

 

 

2500

25.0

5.3

0.9

23, 21, 31

 

 

5000

22.0

4.4

0.8

25, 24, 17

 

2-AA

60

110.7

4.6

4.0

116, 108, 108

Preincubation test

Without metabolic activation


E. coli

DMSO

-

21.7

6.7

-

16, 29, 20

 

Test item

33

20.7

5.5

1.0

15, 26, 21

 

 

100

19.7

2.9

0.9

18, 23, 18

 

 

333

28.0

3.0

1.3

31, 25, 28

 

 

1000

20.3

2.9

0.9

22, 22, 17

 

 

2500

23.0

1.0

1.1

23, 24, 22

 

 

5000

28.3

8.5

1.3

22, 38, 25

 

4-NQO

5

364.3

39.1

16.8

324, 402, 367

With metabolic activation

E. coli

DMSO

-

23.7

7.2

-

20, 32, 19

 

Test item

33

25.0

3.5

1.1

29, 23, 23

 

 

100

29.0

6.1

1.2

22, 32, 33

 

 

333

28.0

6.0

1.2

22, 34, 28

 

 

1000

28.3

7.8

1.2

22, 37, 26

 

 

2500

29.0

2.6

1.2

32, 28, 27

 

 

5000

25.3

1.2

1.1

26, 26, 24

 

2-AA

60

83.0

6.0

3.5

89, 77, 83

Applicant's summary and conclusion

Conclusions:
Under the experimental conditions chosen here, it is concluded that the test substance is not a mutagenic test substance in the bacterial reverse mutation test in the absence and the presence of metabolic activation.