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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:
key study
Study period:
09.03.2018 - 09.11.2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report date:
2018

Materials and methods

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

Test material

Constituent 1
Chemical structure
Reference substance name:
2-(2-aminoethoxy)ethanol
EC Number:
213-195-4
EC Name:
2-(2-aminoethoxy)ethanol
Cas Number:
929-06-6
Molecular formula:
C4H11NO2
IUPAC Name:
2-(2-aminoethoxy)ethan-1-ol
Test material form:
liquid
Specific details on test material used for the study:
Name of test substance: 2-(2-aminoethoxy)ethanol
CAS No.: 929-06-6
Identity: confirmed
Purity/composition: 99.4 area % corrected with the water content
Date of production: 14 Mar 2018

Method

Species / strain
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Metabolic activation system:
The phenobarbital/ß-naphthoflavone induced rat liver S9 fraction was obtained from Moltox Molecular Toxikology, Inc.; Boone, NC 28607; USA. The 5 mL portions of S9 fraction were stored at -70°C to -80°C.
Test concentrations with justification for top dose:
33 μg - 5000 μg/plate
In agreement with the recommendations of current guidelines 5 mg/plate or 5 μL/plate were generally selected as maximum test dose
Vehicle / solvent:
Due to the good solubility of the test substance in water, water was used as vehicle.
Controls
Untreated negative controls:
not specified
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
9-aminoacridine
other: N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 4-nitro-o-phenylenediamine (NOPD)
Remarks:
sterility control: Additional plates were treated with soft agar, S9 mix, buffer, vehicle and the test substance but without the addition of tester strains
Details on test system and experimental conditions:
Standard plate test
The experimental procedure of the standard plate test (plate incorporation method) was based on the method of Ames et al.
• Salmonella typhimurium 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 histidine + 0.5 mM biotin) 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 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 (his+ 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 hindered the counting using the Image Analysis System.
• 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 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 hindered 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 (Perceptive Instruments Ltd., Haverhill, UK). Colonies were counted manually, if precipitation of the test substance hindered the counting using the Image Analysis System.
Rationale for test conditions:
Dose Selection:
According to the current OECD Guideline No. 471 the maximum concentration should be 5000 µg/plate, unless limited by toxicity or solubility of the test item.
In the pre-experiment the concentration range of the test item was 3 – 5000 µg/plate. The pre-experiment met the acceptance criteria, thus, it is reported as experiment I. The concentration range included two logarithmic decades.
The following concentrations were tested in experiment II:
33; 100; 333; 1000; 2500; and 5000 µg/plate
Evaluation criteria:
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 each 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 compatible with the range of the historical positive control data or above
• Fresh bacterial culture containing approximately 109 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 (bacteria strains with high spontaneous mutation rate, like TA 98, TA 100 and E.coli WP2 uvrA) or tripling (bacteria strains with low spontaneous mutation rate, like TA 1535 and TA 1537) of the spontaneous mutation rate in at least one 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 all tester strains were within the range of the historical negative control data under all experimental conditions in at least two experiments carried out independently of each other.
Statistics:
According to the OECD guideline 471, a statistical analysis of the data is not mandatory.

Results and discussion

Test resultsopen allclose all
Key result
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:
not specified
True negative controls validity:
not specified
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not specified
True negative controls validity:
not specified
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not specified
True negative controls validity:
not specified
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not specified
True negative controls validity:
not specified
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not specified
True negative controls validity:
not specified
Positive controls validity:
valid
Additional information on results:
A weak bacteriotoxic effect (slight decrease in the number of his+ revertants) was observed in the standard plate test using test strain TA 1537 and in the preincubation assay using TA 1537 and TA 98 without S9 mix at a concentration of 5000 μg/plate, only.
No test substance precipitation was found with and without S9 mix.

Applicant's summary and conclusion

Conclusions:
A relevant increase in the number of his+ or trp+ revertants (factor ≥ 2: TA 100, TA 98 and E.coli WP2 uvrA or factor ≥ 3: TA 1535 and TA 1537) was not observed in the standard plate test or in the preincubation test without S9 mix or after the addition of a metabolizing system.
Executive summary:

Under the experimental conditions chosen here, it is concluded that 2-(2 - aminoethoxy)ethanol is not a mutagenic test substance in the bacterial reverse mutation test in the absence and the presence of metabolic activation.