Sodium 2-mercaptoethanolate

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

26th of may 1983 and Draft Proposal of 1991

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Sodium 2-mercaptoethanolate

EC Number:

253-523-3

EC Name:

Sodium 2-mercaptoethanolate

Cas Number:

37482-11-4

Molecular formula:

C2H6OS.Na

IUPAC Name:

sodium 2-sulfanylethan-1-olate

Test material form:

liquid

Specific details on test material used for the study:

- Name of the test item (as cited by study report): 2-mercaptoethanol, sodium salt
- Purity: 45.21%
- Batch No.: 927056
- Appearance: Yellow, liquid

Method

Target gene:

his

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced rat liver S-9 mix

Test concentrations with justification for top dose:

0, 125, 250, 1000, 2000 ug/plate. The highest concentration (2000 µg/plate) showing moderate toxicity: decreased by approximately 50% of the number of revertant.

Vehicle / solvent:

Distilled water

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

sodium azide

mitomycin C

other: 2-anthramine (2AM) and danthron (DTH)

Details on test system and experimental conditions:

- Preincubation method : the test substance solution (maximum volume: 0.1 ml), 0.5 ml of S9 mix and 0.1 mL of the strain were incubated for 60 minutes at 37°C prior adding the overlay agar and pouring onto the surface of a minimum agar plate.
- Direct plate incorporation method: the test substance solution (maximum volume: 0.1 ml), 0.5 mL of S9 mix (when required) and 0 .1 mL of the strain were added to 2 mL molten agar containing traces of histidine and biotin and maintained at +45°C. After rapid homogenization, the mixture was spread out on a Petri plate containing minimum medium.
- The methods used were the direct plate incorporation method (both tests without S9 mix, first test with S9 mix) or the preincubation method (second test with S9 mix) described by Maron and Ames.

Evaluation criteria:

The following criteria were used as an aid for determining a positive response: a reproducible and significant dose relationship using a linear regression analysis, considered as significant if p<0 .05 (for n = 18 values, the correlation coefficient must be r >0 .47) and/or a reproducible and significant increase (i.e. a doubling in the number of revertants for at least one of the tested strains when compared to that of the negative and/or solvent controls) for at least one of the tested concentrations.
A test substance is considered as non-mutagenic in this test system if the above two criteria are not fully met. Biological and statistical significances were considered during the evaluation.

Results and discussion

Test results

Key result

Species / strain:

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

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: see additional information on results

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

CYTOTOXICITY IN PRELIMINARY TEST
- Without metabolic activation moderate effects on bacterial lawn at 2260 ug/plate, slight effects at 1130 ug/plate; number of revertants decreased to ca. 50% of solvent control at 1130 ug/plate and ca. 7% at 2260 ug/plate
- With metabolic activation no effects on bacterial lawn but decrease in the number of revertants at 452 and 1130 μg/plate (ca. 50% of solvent control), at 2260 μg/plate ca. 7%.

GENOTOXIC EFFECTS IN THE MAIN STUDY
- The test substance 2-Mercaptoethanol, sodium salt did not induce any significant increase in the number of revertants, with or without S9 mix, in any of the 5 strains tested.
- Negative and positive controls were valid.
- The high dose level decreased the number of revertants to ca. 50% of the solvent control in TA100 and TA102 (with and without MA), to ca. 70% in TA98 and TA1537 (with and without MA) in at least one out of 2 trials.