Potassium (2S)-4-carboxy-2-(tetradecanoylamino)butanoate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

In Vitro Bacterial Gene Mutation:

Ames test: Negative without and with metabolic activation, OECD 471, EU Method B.13/14 and EPA OPPTS 870.5100, Hargitai (2012)

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 November 2011 to 15 December 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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

Target gene:

histidine locus (S. typhimurium)
tryptophan locus (E. coli)

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Details on mammalian cell type (if applicable):

- Type and identity of media: Nutrient Broth No.2.
- Properly maintained: yes. The strains are stored at -80 ± 10 ºC at the test facility. Frozen permanent cultures of the tester strains were prepared from fresh, overnight cultures to which DMSO was added as a cryoprotective agent. The frozen bacterial cultures were thawed at room temperature and 200 μL inoculum were used to inoculate each 50 mL of Nutrient Broth No.2 (Section 5.4.2.) for the overnight cultures in the assay. The cultures were incubated for 10 - 14 hours at 37 °C in a Gyrotory water bath shaker.
- Periodically checked for karyotype stability: yes, the phenotypes of the tester strains used in assays with regard to membrane permeability (rfa), UV sensitivity (uvrA and uvrB), ampicillin resistance (amp), were checked regularly.
- Periodically "cleansed" against high spontaneous background: yes, spontaneous mutation frequencies were checked regularly.
- Culture viability: The viability of each testing culture was determined by plating 0.1 mL of the10^5, 10^6, 10^7 and 10^8 dilutions prepared by sterile physiological saline on Nutrient Agar plates. The viable cell number of the cultures was determined by manual counting after approximately 24-hour incubation at 37°C.

Additional strain / cell type characteristics:

other: S. typhimurium TA98 and TA100: rfa, uvrB and pKM101; S. typhimurium TA1535 and TA1537: rfa and uvrB; E coli: uvrA.

Metabolic activation:

with and without

Metabolic activation system:

activated rat liver S9 fraction

Test concentrations with justification for top dose:

5000, 1581, 500, 158.1, 50, 15.81, 5 and 1.581 μg/plate.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Distilled water.
- Justification for choice of solvent/vehicle: The solubility of the test material was examined in Distilled water, Dimethyl sulfoxide (DMSO) and N,N-Dimethylformamide (DMF). The test material was insoluble using DMSO or DMF as solvent at 100 mg/mL concentration, but a proper formulation was achieved in Distilled water at the same concentration. Therefore, Distilled water was chosen for solvent of the study.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

distilled water and DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

sodium azide

methylmethanesulfonate

other: 4-nitro-1,2-phenylene-diamine; 2-aminoanthracene

Remarks:

Positive control vehicles; DMSO and distilled water.

Details on test system and experimental conditions:

EXPERIMENTAL PROCEDURE: Two independent tests were run, initial and confirmatory mutation assays.

METHOD OF APPLICATION: preincubation method.
Before the overlaying, 50 μL of the test material formulation (or solvent or reference control), 100 μL of the overnight culture of the tester strains (cultured in Nutrient Broth No.2.) and 0.5 mL of the S9 mix or phosphate buffer (pH 7.4) were added into appropriate tubes to provide direct contact between bacteria and the test material. These tubes were gently mixed and incubated for 20 min at 37ºC in a shaking incubator.
After the incubation period, 2 mL of molten top agar (kept at 45°C) were added to the tubes; the content was mixed and poured on the surface of minimal glucose agar plates. The entire test consisted of non-activation and an activation test conditions, with the addition of untreated, negative and positive controls. After preparation, the plates were incubated at 37°C for 48 hours.

DURATION
- Preincubation period: 20 minutes.
- Exposure duration: 48 hours.

NUMBER OF REPLICATIONS: Cultures were performed in triplicate for each concentration level and control.

EVALUATION: The colony numbers on the untreated / negative (solvent) / positive control and test material treated plates were determined by manual counting. Visual examination of the plates was also performed; precipitation or signs of growth inhibition (if any) were recorded and reported. The mean number of revertants per plate, the standard deviation and the mutation factor* values were calculated for each concentration level of the test material and for the controls.
Mutation factor (MF): mean number of revertants on the test material plate / mean number of revertants on the vehicle control plate.
Note: In the confirmatory mutation assay in S. typhimurium TA100 strain at 1581 μg/plate concentration without metabolic activation, one of the plates was infected. In this case, the mutation factor value was calculated using the data of the remaining two replicates.

DETERMINATION OF CYTOTOXICITY
- Method: Assessment of the effects on the background lawn.

Evaluation criteria:

Criteria for a Positive Response:
A test material was considered mutagenic if:
- a dose–related increase in the number of revertants occurred and/or;
- a reproducible biologically relevant positive response for at least one of the dose groups occurred in at least one strain with or without metabolic activation.

An increase was considered biologically relevant if:
- in all strains: the number of reversion more than twice higher than the reversion rate of the negative (solvent) control.
According to the guidelines, statistical method may be used as an aid in evaluating the test results. However, statistical significance should not be the only determining factor for a positive response.

Criteria for a Negative Response:
A test article was considered non-mutagenic if it produced neither a dose-related increase in the number of revertants nor a reproducible biologically relevant positive response at any of the dose groups, with or without metabolic activation.

Criteria for Validity:
The study was considered valid if:
- the number of revertant colonies of the negative (solvent) and positive controls were in the historical control range in all strains of the main tests;
- at least five analysable concentrations were presented in all strains of the main tests.

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Cytotoxic effect was observed in all Salmonella typhimurium strains at 5000 and 1581 μg/plate concentrations without metabolic activation

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

True negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Cytotoxic effect was observed in all Salmonella typhimurium strains at 5000 and 1581 μg/plate concentrations without metabolic activation

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

True negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Cytotoxic effect was observed in all Salmonella typhimurium strains at 5000 and 1581 μg/plate concentrations without metabolic activation

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

True negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Cytotoxic effect was observed in all Salmonella typhimurium strains at 5000 and 1581 μg/plate concentrations without metabolic activation

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

True negative controls validity:

not examined

Positive controls validity:

valid

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

True negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: No precipitation was observed in the main tests.

RANGE-FINDING/SCREENING STUDIES:
The revertant colony numbers and the inhibition of the background lawn of auxotrophic cells of two of the tester strains (Salmonella typhimurium TA98 and TA100) were determined in triplicate using the pre-incubation method at concentrations of 5000, 2500, 1000, 316, 100, 31.6 and 10 μg/plate of the test material with and without metabolic activation.
The observed numbers of revertant colonies were mostly in the normal range. Higher or lower colony counts compared to the solvent control were observed at some non-cytotoxic concentrations; however, they were without biological significance and in the historical control range in all cases. Therefore, they were considered to reflect the biological variability of the test system.
Inhibitory, cytotoxic effect (reduced / slightly reduced background lawn development, in some cases pinpoint colonies were also detected) of the test material was observed in the Preliminary Range Finding Test in both examined strains at 5000, 2500, 1000 and 316 μg/plate concentrations without metabolic activation and at 5000 μg/plate concentration with metabolic activation. Reduced numbers of revertant colonies were observed in S. typhimurium TA100 tester strain at 2500, 1000 and 316 μg/plate concentrations with metabolic activation, but background inhibition was not detected in these cases.
No precipitation was observed in the preliminary experiment.
Based on the observed result of the preliminary experiment, 5000 μg/plate concentration was selected as the highest examined dose in the main test and lower concentrations will be evenly spaced by approximately half log intervals to cover the range from cytotoxicity to no cytotoxicity.

COMPARISON WITH HISTORICAL CONTROL DATA: The mean values of revertant colonies of the solvent control plates were within the historical control data range, the reference mutagens showed the expected increase in the number of revertant colonies.

ADDITIONAL INFORMATION ON CYTOTOXICITY: Inhibitory, cytotoxic effect (reduced / slightly reduced background lawn development and / or reduced number of revertant colonies, in some cases pinpoint colonies were also detected) of the test material was observed in the Initial Mutation Test in all S. typhimurium strains at 5000, 1581 and 500 μg/plate concentration without metabolic activation and at 5000 μg/plate concentration with metabolic activation, and in S. typhimurium TA100 strain at 1581 μg/plate concentration with metabolic activation. Similar inhibitory, cytotoxic effect was observed in the Confirmatory Mutation Test in all S. typhimurium strains at 5000 and 1581 μg/plate concentrations without metabolic activation; in S. typhimurium TA100, TA1535 and TA1537 strains at 500 μg/plate concentration without metabolic activation; and in S. typhimurium TA98, TA100 and TA15357 strains at 5000 μg/plate concentrations with metabolic activation; and in S. typhimurium TA100 strain at 1581 and 500 μg/plate concentration with metabolic activation.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Table 1: Initial Mutation Assay Results

Concentration (µg/plate)		S. typhimurium Tester Strains								E. coli
		TA98		TA100		TA1535		TA1537		WP2 uvrA
		- S9	+ S9	- S9	+ S9	- S9	+ S9	- S9	+ S9	- S9	+ S9
Untreated control	Mean	27.3	38.0	89.3	102.0	6.7	12.7	6.3	9.7	24.3	39.0
	MF	0.89	1.13	0.95	0.98	0.95	1.09	0.73	0.71	0.94	0.93
DMSO control	Mean	28.0	33.3	--	107.7	--	11.0	6.7	8.7	--	37.0
	MF	0.91	0.99	--	1.04	--	0.94	0.77	0.63	--	0.88
Distilled Water Control	Mean	30.7	33.7	93.7	103.7	7.0	11.7	8.7	13.7	26.0	42.0
	MF	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
5000	Mean	0.0*	15.0*	0.0*	29.7	0.7*	6.0*	0.0*	4.0	17.3	30.3
	MF	0.00	0.45	0.00	0.29	0.10	0.51	0.00	0.29	0.67	0.72
1581	Mean	4.3*	27.7	30.3*	42.0	4.0*	7.3	1.0*	7.0	22.7	30.0
	MF	0.14	0.82	0.32	0.41	0.57	0.63	0.12	0.51	0.87	0.71
500	Mean	7.7*	33.0	68.7*	52.7	4.0*	8.3	2.3*	8.0	23.7	39.7
	MF	0.25	0.98	0.73	0.51	0.57	0.71	0.27	0.59	0.91	0.94
158.1	Mean	27.3	32.0	94.7	62.7	6.7	12.7	9.0	9.7	23.7	40.3
	MF	0.89	0.95	1.01	0.60	0.95	1.09	1.04	0.71	0.91	0.96
50	Mean	23.3	33.3	99.3	86.7	7.3	13.0	8.3	11.7	19.7	42.3
	MF	0.76	0.99	1.06	0.84	1.05	1.11	0.96	0.85	0.76	1.01
5	Mean	29.0	36.3	96.3	106.0	9.7	12.3	11.0	11.0	27.7	34.3
	MF	1.08	1.03	1.02	1.38	1.06	1.27	0.80	1.06	0.82	1.08
1.581	Mean	26.3	32.7	97.0	103.7	5.0	11.7	7.3	8.7	21.0	30.3
	MF	0.86	0.97	1.04	1.00	0.71	1.00	0.85	0.63	0.81	0.72

MF = Mutation factor

* = Growth inhibition observed.

Bold italics = Cytotoxic effects observed.

Table 2: Confirmatory Mutation Assay Results

Concentration (µg/plate)		S. typhimurium Tester Strains								E. coli
		TA98		TA100		TA1535		TA1537		WP2 uvrA
		- S9	+ S9	- S9	+ S9	- S9	+ S9	- S9	+ S9	- S9	+ S9
Untreated control	Mean	25.7	35.0	92.3	127.7	10.0	8.3	5.3	9.3	30.7	41.0
	MF	1.03	0.86	1.02	1.02	1.20	0.86	1.45	1.00	0.94	0.91
DMSO control	Mean	19.7	32.0	--	117.3	--	11.7	3.0	9.0	--	40.7
	MF	0.79	0.79	--	0.94	--	1.21	0.82	0.96	--	0.90
Distilled Water Control	Mean	25.0	40.7	90.7	125.0	8.3	9.7	3.7	9.3	32.7	45.0
	MF	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
5000	Mean	1.3*	14.0	2.0*	27.0*	0.3*	8.0	0.0*	2.0	23.7	33.3
	MF	0.05	0.34	0.02	0.22	0.04	0.83	0.00	0.21	0.72	0.74
1581	Mean	3.0*	21.7	43.5*	46.7*	3.7*	6.0	0.7*	4.7	26.7	38.3
	MF	0.12	0.53	0.48	0.37	0.44	0.62	0.18	0.50	0.82	0.85
500	Mean	13.3	28.0	61.7*	49.3	6.3*	7.3	1.7*	5.0	30.7	40.7
	MF	0.53	0.69	0.68	0.39	0.76	0.76	0.45	0.54	0.94	0.90
158.1	Mean	25.0	29.0	92.7	81.3	7.7	6.0	4.3	8.0	28.0	52.7
	MF	1.00	0.71	1.02	0.65	0.92	0.62	1.18	0.86	0.86	1.17
50	Mean	24.0	33.0	87.0	94.0	7.3	10.3	6.3	7.0	28.7	41.0
	MF	0.96	0.81	0.96	0.75	0.88	1.07	1.73	0.75	0.88	0.91
5	Mean	29.0	33.7	84.0	96.0	6.0	9.3	5.0	7.3	34.3	52.7
	MF	1.16	0.83	0.93	0.77	0.72	0.97	1.36	0.79	1.05	1.17
1.581	Mean	26.7	30.7	96.7	119.3	4.0	15.3	5.7	7.3	34.3	38.7
	MF	1.07	0.75	1.07	0.95	0.48	1.59	1.55	0.79	1.05	0.86

MF = Mutation factor

* = Growth inhibition observed.

Bold italics = Cytotoxic effects observed.

 

Conclusions:

Under the conditions of this mutagenicity assay the test material did not induce gene mutations by base pair changes or frameshifts in the genome of the bacterial strains used. In the Initial Mutation Test and Confirmatory Mutation Tests none of the observed revertant colony numbers were above the respective biological threshold value. There were no reproducible dose-related trends and no indication of any treatment related effect.

Executive summary:

The mutagenic potential of the test material, was determined in an Ames test, conducted with the bacterial strains S. typhimurium TA98, TA100 TA1535 and TA1537, and E. coli WP2 uvrA. The study was conducted in accordance with the OECD 471, EU Method B.13/14 and EPA OPPTS 870.5100 guidelines.

Bacterial cultures were exposed to the test material in triplicate, using the pre-incubation method at concentrations up to 5000 µg/plate either in the presence or absence of a metabolic activation system. Two independent experiments were performed the initial mutation assay followed by the confirmatory assay.

Under the conditions of this mutagenicity assay the test material did not induce gene mutations by base pair changes or frameshifts in the genome of the bacterial strains used. In the Initial Mutation Test and Confirmatory Mutation Tests none of the observed revertant colony numbers were above the respective biological threshold value. There were no reproducible dose-related trends and no indication of any treatment related effect.

In conclusion the test material is considered to be non-mutagenic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In Vitro Bacterial Gene Mutation

In the key study (Hargitai, 2012) the mutagenic potential of the test material, was determined in an Ames test, conducted with the bacterial strains S. typhimurium TA98, TA100 TA1535 and TA1537, and E. coli WP2 uvrA. The study was conducted in accordance with the OECD 471, EU Method B.13/14 and EPA OPPTS 870.5100 guidelines.

Bacterial cultures were exposed to the test material in triplicate, using the pre-incubation method at concentrations up to 5000 µg/plate either in the presence or absence of a metabolic activation system. Two independent experiments were performed the initial mutation assay followed by the confirmatory assay.

Under the conditions of this mutagenicity assay the test material did not induce gene mutations by base pair changes or frameshifts in the genome of the bacterial strains used. In the Initial Mutation Test and Confirmatory Mutation Tests none of the observed revertant colony numbers were above the respective biological threshold value. There were no reproducible dose-related trends and no indication of any treatment related effect.

In conclusion the test material is considered to be non-mutagenic.

Justification for classification or non-classification

In accordance with OECD guideline 471, the negative result from the Ames test indicates that the test material is not mutagenic in S. typhimurium TA98, TA100 TA1535 and TA1537, and E. coli WP2 uvrA. On this basis, the test substance is not classified for genetic toxicity in accordance with Regulation (EC) No. 1272/2008.