2-ethylhexyl mercaptoacetate

Genetic toxicity: in vitro

Administrative data

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:

From 28 April to 24 June 1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1994

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

2-ethylhexyl mercaptoacetate

EC Number:

231-626-4

EC Name:

2-ethylhexyl mercaptoacetate

Cas Number:

7659-86-1

Molecular formula:

C10H20O2S

IUPAC Name:

2-ethylhexyl 2-sulfanylacetate

Constituent 2

Reference substance name:

2-ethylhexyl thioglycolate

IUPAC Name:

2-ethylhexyl thioglycolate

Details on test material:

- Name of test material (as cited in study report): 2-ethylhexyl thioglycolate
- Expiration date of the lot/batch: January 1994
- Storage condition of test material: at room temperature, away from light

Method

Target gene:

This test enables the detection of base-pair substitution and frameshift mutagens. Mutagenic substances can induce reversion in histidine-deficient strains, which are then able to grow and form colonies in a histidine-limited medium, while non-revertants can not.

Species / strain

Species / strain / cell type:

S. typhimurium, other: TA98, TA100, TA102, TA1535 & TA1537

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

S9 mix

Test concentrations with justification for top dose:

Without S9: 2.5, 5, 10, 20 & 50 µg/plate
With S9: 250, 500, 1000, 2000 & 4000 µg/plate (1st assay); 31.25, 62.5, 125, 250 & 500 µg/plate (2nd assay)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: not reported but commonly used for this type of study.

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Without S9 mix: · 1 µg/plate of sodium azide (NaN3): TA 1535 and TA 100 strains, · 50 µg/plate of 9-Aminoacridine (9AA): TA 1537 strain, · 0.5 µg/plate of 2-Nitrofluorene (2NF): TA 98 strain, · 0.5 µg/plate of Mitomycin C (MMC): TA 102 strain. With S9 mi

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation) and preincubation
- Type and identity of media:
Direct plate incorporation method:
Molten agar containing traces of histidine and biotin and maintained at 45°C. Then Petri plate containing minimum medium.

Preincubation method:
Minimum agar plate.

DURATION
- Preincubation period: 14 hours
- Exposure duration: 48 to 72 hours

SELECTION AGENT (mutation assays): Histidine

NUMBER OF REPLICATIONS: 2 independent tests, using 3 plates/concentration

DETERMINATION OF CYTOTOXICITY
- other: observation whether the bacterial lawn is sparse and whether the number of colonies is decreased.

Evaluation criteria:

Positive response if:
- a reproducible and significant (if p <= 0.05) dose relationship, and/or
- a reproducible and significant (doubling in the number of revertants) increase

Test valid because:
- Results of the negative and vehicle controls in the range of corresponding historical data, and
- Results of the positive control higher than results of negative and vehicle controls and in the range of corresponding historical data

Statistics:

Linear regression analysis

Results and discussion

Test results

Species / strain:

S. typhimurium, other: TA98, TA100, TA102, TA1535 & TA1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Without S9: >= 50 µg/plate|with S9: >= 5000 µg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA:
The negative and solvent control results were equivalent to those usually obtained in the laboratory. The number of revertants induced by the
positive controls was higher than the controls, indicating the sensitivity of the test.
RANGE-FINDING/SCREENING STUDIES:
Precipitation was observed from 500 µg/plate in the first cytotoxicity test conducted without S9. It was not observed in the corresponding test
conducted with S9.

COMPARISON WITH HISTORICAL CONTROL DATA:
The negative and solvent control results were equivalent to those usually obtained in the laboratory. The number of revertants induced by the
positive controls was higher than the controls, indicating the sensitivity of the test.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Table 1: Mean Revertants per Plate – Direct plate incorporation method

Test Material	TA-1535		TA-1537		TA-102		TA-98		TA-100
	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Nonactivation
Negative Control	11	2	12	2	160	17	18	3	92	4
Solvent Control	11	2	6	2	219	8	12	4	71	16
2.5 µg/plate	13	1	9	1	196	16	18	1	80	5
5 µg/plate	13	3	11	2	199	22	13	3	81	4
10 µg/plate	9	3	7	2	245	20	14	4	80	13
20 µg/plate	11	2	7	1	222	33	13	1	84	4
50 µg/plate	5	1	8	2	226	8	17	2	86	12
Positive Control	188	36	149	13	1005	236	109	10	323	23
Activation
Solvent Control	13	1	10	1	297	20	25	3	108	7
250 µg/plate	13	4	8	1	261	14	24	4	101	12
500 µg/plate	10	5	7	2	278	35	22	7	119	7
1000 µg/plate	11	3	6	1	304	23	22	6	115	6
2000 µg/plate	13	2	8	2	320	27	20	5	105	7
4000 µg/plate	11	1	10	1	324	31	23	3	100	28
Positive Control	252	35	147	9	895	66	1767	131	1573	43

Table 2: Mean Revertants per Plate – Preincubation method

Test Material	TA-1535		TA-1537		TA-102		TA-98		TA-100
	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Nonactivation
Negative Control	10	4	12	3	261	8	15	1	79	5
Solvent Control	7	3	13	2	210	8	15	5	69	8
2.5 µg/plate	9	3	13	3	254	23	14	4	84	4
5 µg/plate	7	1	10	3	258	10	18	5	84	8
10 µg/plate	6	3	13	2	264	11	17	2	74	7
20 µg/plate	8	0	13	4	238	30	14	4	82	10
50 µg/plate	7	2	9	2	353	15	20	2	76	7
Positive Control	232	5	185	21	1676	185	133	12	296	23
Activation
Solvent Control	9	4	12	1	414	23	25	1	110	19
31.25 µg/plate	13	4	9	2	383	11	24	1	98	13
62.5 µg/plate	10	1	13	3	354	24	30	8	106	6
125 µg/plate	12	4	9	3	355	41	24	5	91	4
250 µg/plate	11	0	9	1	348	7	30	3	95	4
500 µg/plate	4	3	6	3	344	26	14	2	22	39
Positive Control	158	5	222	9	871	76	1710	75	1397	27

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

The test substance was found to be negative in the in vitro genotoxicity Ames assay both in the presence and absence of metabolic activation.

Executive summary:

The genotoxicity of the substance was determined in a reverse mutation assay conducted in vitro with salmonella typhimurium TA 1535, TA 1537, TA 102, TA 98 and TA 100 according to the OECD Guideline 471. Concentrations tested ranged from 2.5 to 50 µg/plate and from 31.5 to 4000 µg/plate in the absence of S9 and in the presence of S9, respectively. The test substance did not induce any significant increase in the number of revertants, with or without S9 mix, in any of the 5 strains.