4-(cyclohexylamino)butane-1-sulfonic acid

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 April 2019 - 26 April 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

21 July 1997

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Version / remarks:

31 May 2018

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

4-(cyclohexylamino)butane-1-sulfonic acid

EC Number:

629-080-0

Cas Number:

161308-34-5

Molecular formula:

C10 H21 N O3 S

IUPAC Name:

4-(cyclohexylamino)butane-1-sulfonic acid

Test material form:

solid

Details on test material:

Physical Description: White solid
Storage Conditions: At room temperature

Method

Target gene:

S. typhimurium: Histidine gene
E. coli: Tryptophan gene

Species / strain

Species / strain 1

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain 2

Species / strain / cell type:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

Type and composition of metabolic activation system:
- source of S9 : rat liver S9-mix induced by Aroclor 1254 (500 mg/kg bw)
- method of preparation of S9 mix: S9-mix per 10 mL: 30 mg NADP, 15.2 mg glucose-6-phosphate in 5.5 mL Milli-Q water; 2 mL 0.5 M sodium phosphate buffer pH 7.4; 1 mL 0.08 M MgCl2 solution; 1 mL 0.33 M KCl solution. The solution was filter (0.22 μm)-sterilized and 0.5 mL S9-fraction was added
- concentration of S9 in S9 mix: 5%
- quality controls of S9: Each S9 batch was characterized with the mutagens benzo-(a)-pyrene and 2-aminoanthracene, which require metabolic activation, in tester strain TA100 at concentrations of 5 μg/plate and 2.5 μg/plate, respectively

Test concentrations with justification for top dose:

Justification for top dose: 5 mg is the recommended maximum test concentration according to the guideline.

Dose-range finding test (without and with S9-mix; tester strains TA100 and WP2uvrA): 1.7, 5.4, 17, 52, 164, 512, 1600 and 5000 µg/plate (reported as part of experiment 1)

First experiment (without and with S9; tester strains TA1535, TA1537 and TA98): 52, 164, 512, 1600, 5000 μg/plate

Second experiment (without and with S9-mix, tester strains WP2uvrA, TA1535, TA1537, TA 98 and TA100): 52, 164, 512, 1600, 5000 μg/plate

Vehicle / solvent:

The vehicle of the test item was Milli-Q water

Controls

Untreated negative controls:

other: Not applicable

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

2-nitrofluorene

sodium azide

methylmethanesulfonate

other: 2-aminoanthracene; ICR-191

Remarks:

For details on positive control substances, see Table 1 and Table 2

Details on test system and experimental conditions:

NUMBER OF REPLICATIONS:
- Doses levels were tested in triplicate in each strain.

METHODS:
Direct plating assay:
The following solutions were successively added to 3 mL molten top agar: 0.1 mL of a fresh bacterial culture (1E9 cells/mL) of one of the tester strains, 0.1 mL of a dilution of the test item in Milli-Q water and either 0.5 mL S9-mix (in case of activation assays) or 0.5 mL 0.1 M phosphate buffer (in case of non-activation assays). The ingredients were mixed on a Vortex and the content of the top agar tube was poured onto a selective agar plate. After solidification of the top agar, the plates were inverted and incubated in the dark.
Pre-incubaton assay:
The solution in the direct plating assay were pre-incubated for 30 ± 2 minutes by 70 rpm at 37 ± 1°C before added to 3 mL molten top agar

DURATION
- Exposure duration: 48 ± 4 h (in the dark at 37.0 ± 1.0 °C)

DETERMINATION OF CYTOTOXICITY
- Method: the reduction of the bacterial background lawn, the increase in the size of the microcolonies and the reduction of the revertant colonies.
- Other: precipitation of the test item was recorded.

COLONY COUNTING
The revertant colonies were counted automatically with the Sorcerer Colony Counter. Plates with sufficient test item precipitate to interfere with automated colony counting were counted manually. Evidence of test item precipitate on the plates and the condition of the bacterial background lawn were evaluated when considered necessary, macroscopically and/or microscopically by using a dissecting microscope.

ACCEPTABILITY CRITERIA
A Salmonella typhimurium reverse mutation assay and/or Escherichia coli reverse mutation assay is considered acceptable if it meets the following criteria:

a) The vehicle control and positive control plates from each tester strain (with or without S9-mix) must exhibit a characteristic number of revertant colonies when compared against relevant historical control data generated at Charles River Den Bosch.
b) The selected dose-range should include a clearly toxic concentration or should exhibit limited solubility as demonstrated by the preliminary toxicity range-finding test or should extend to 5 mg/plate.
c) No more than 5% of the plates are lost through contamination or some other unforeseen event. If the results are considered invalid due to contamination, the experiment will be repeated.

Rationale for test conditions:

According to guideline

Evaluation criteria:

A test item is considered negative (not mutagenic) in the test if:
a) The total number of revertants in tester strain TA100 or WP2uvrA is not greater than two times the concurrent control, and the total number of revertants in tester strains TA1535, TA1537 or TA98 is not greater than three times the concurrent control.
b) The negative response should be reproducible in at least one follow up experiment.

A test item is considered positive (mutagenic) in the test if:
a) The total number of revertants in tester strain TA100 or WP2uvrA is greater than two times the concurrent control, or the total number of revertants in tester strains TA1535, TA1537 or TA98 is greater than three times the concurrent control.
b) In case a repeat experiment is performed when a positive response is observed in one of the tester strains, the positive response should be reproducible in at least one follow up experiment.

any increase in the total number of revertants should be evaluated for its biological relevance including a comparison of the results with the historical control data range.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Remarks:

See explanation below

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

First Experiment:
Precipitation:
Precipitation of the test item on the plates was not observed at the start or at the end of the incubation period in any tester strain.

Cytotoxicity:
There was no reduction in the bacterial background lawn and no biologically relevant decrease in the number of revertants at any of the concentrations tested in all tester strains in the absence and presence of S9-mix.

Mutagenicity:
In the direct plate test, no increase in the number of revertants was observed upon treatment with the test item.

Second Experiment:
Precipitation:
Precipitation of the test item on the plates was not observed at the start or at the end of the incubation period.

Cytotoxicity:
There was no reduction in the bacterial background lawn and no biologically relevant decrease in the number of revertants at any of the concentrations tested in all tester strains in the absence and presence of S9-mix.

Mutagenicity:
In the pre-incubation test, no increase in the number of revertants was observed upon treatment with the test item.

In tester strain TA1535 in the absence of S9-mix, the test item induced an up to 4.0-fold increase in the number of revertant colonies compared to the solvent control in a single experiment. The increases were not dose dependent and fell within the historical control data range. Therefore, the increases are considered to be not biologically relevant.

Acceptability criteria:
All bacterial strains showed negative responses over the entire dose-range, i.e. no significant dose-related increase in the number of revertants in two independently repeated experiments.
The negative and strain-specific positive control values were within the laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly.

Details on results are included below.

Applicant's summary and conclusion

Conclusions:

Based on the results of an Ames test, performed according to OECD guideline 471 and in accordance with GLP principles, 4-(cyclohexylamino)butane-1-sulfonic acid is concluded to be not mutagenic in the Salmonella typhimurium reverse mutation assay and in the Escherichia coli reverse mutation assay.

Executive summary:

A bacterial reverse mutation test was performed according to OECD guideline 471 and in accordance with GLP principles. The negative and strain-specific positive control values were within the laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly. The test item did not induce a significant dose-related increase in the number of revertant (His⁺) colonies in each of the four tester strains (TA1535, TA1537, TA98 and TA100) and in the number of revertant (Trp⁺) colonies in tester strain WP₂uvrA both in the absence and presence of S9 -metabolic activation when tested up to and including the recommended top concentration. These results were confirmed in a follow-up experiment. Based on the results of this study it is concluded that the test item is not mutagenic in the Salmonella typhimurium reverse mutation assay and in the Escherichia colireverse mutation assay.