(2-hydroxyethyl)ammonium mercaptoacetate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

GLP compliance:

yes

Type of assay:

mammalian erythrocyte micronucleus test

Test material

Test material information

Constituent 1

Reference substance name:

Sodium mercaptoacetate

EC Number:

206-696-4

EC Name:

Sodium mercaptoacetate

Cas Number:

367-51-1

Molecular formula:

C2H4O2S.Na

IUPAC Name:

sodium sulfanylacetate

Details on test material:

Test article name: Sodium thioglycolate
CAS no. : 367-51-1
Source: Bruno Bock Chemische Fabrik GmbH & Co KG
Batch no. : 10640
Purity: 99.4%

Test animals

Species:

mouse

Strain:

NMRI

Sex:

male/female

Details on test animals or test system and environmental conditions:

- Animals . 
. Source: Harlan Winkelmann GmbH D-33178 Borchen
. Number of Animals: 72 (36 males/36 females), 6 males and 6 females per  group
. Initial Age at Start of Acclimatisation: 8-10 weeks
. Acclimatisation: minimum 5 days
. Initial Body Weight at Start of Treatment: males mean value 37.1 g (SD  ± 2.9 g) females mean value 31.5 g (SD ± 1.9 g)

- Environmental conditions
. Housing: single Cage Type: Makrolon Type I, with wire mesh top (EHRET  GmbH, D-79302 Emmendingen)
. Bedding: granulated soft wood bedding (Harlan Winkelmann GmbH, D-33178  Borchen)
. Temperature 22 ± 3 °C
. Relative humidity 30 - 70 %
. Artificial light 6.00 a.m. - 6.00 p.m.

- Food and water
. Feed: pelleted standard diet, ad libitum (Harlan Winkelmann GmbH,  D-33178 Borchen)
. Water: tap water, ad libitum, (Gemeindewerke, D-64380 Roßdorf)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

Name: deionised water         
Route and Frequency of Administration: orally, once         
Volume Administered: 10 mL/kg b.w.

Duration of treatment / exposure:

single administration

Frequency of treatment:

single

Post exposure period:

24 and 48 hours

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

62.5 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

125 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

250 mg/kg bw/day

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control(s):

Name: CPA; Cyclophosphamide         
Dissolved in: deionised water         
Dosing: 40 mg/kg b.w.         
Route and frequency of administration: orally, once         
Volume administered: 10 mL/kg b.w.

Examinations

Tissues and cell types examined:

Bonne marrow

Details of tissue and slide preparation:

- Preparation of the bone marrow smears
Ten animals (5 males, 5 females) per test group (all groups after 24  hours and only the high dose group after 48 hours) were killed by CO2  inhalation, following by bleeding. The femurs of the animals were removed  and the bone marrow was flushed out using foetal calf serum. After  centrifugation, the supernatant was removed and the cells in the sediment  were resuspended by shaking. A drop of this cell suspension was placed  and spread on a slide. The slides were air dried and stained with  May-Grünwald. The slides were coded so that the scorer is unaware of the  treatment group of the slide under evaluation ("blind" scoring).

- Microscopic examination of the slides
For each animal, the number of the micronucleated polychromatic  erythrocytes (MPE) was counted in 2000 polychromatic erythrocytes; the  polychromatic (PE) and normochromatic (NE) erythrocyte ratio was  established by scoring a total of 1000 erythrocytes (PE + NE). 

Evaluation criteria:

The study was considered valid as the following criteria are met:
- the negative controls are in the range of our historical control data.
- the positive controls are in the range of our historical control data.
- at least 4 animals per group and sex can be evaluated
- PCE to erythrocyte ratio should not be less than 20 % of the negative  control.

A test item is classified as mutagenic if it induces either a  dose-related increase or a clear increase in the number of micronucleated  polychromatic erythrocytes in a single dose group. 

Statistics:

Statistical methods (nonparametric Mann-Whitney test (8)) will be used  as an aid in evaluating the results. However, the primary point of  consideration is the biological relevance of the results. A test item that fails to produce a biological relevant increase in the  number of micronucleated polychromatic erythrocytes is considered  non-mutagenic in this system.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

clinical signs

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

As estimated by a pre-experiment 250 mg Sodium Thioglycolate 98%, Pure  per kg b.w. was suitable.
The mean number of polychromatic erythrocytes was not decreased after  treatment with the test item as compared to the mean value of PCEs of the  vehicle control indicating that Sodium Thioglycolate 98%, Pure had no  cytotoxic properties in the bone marrow. In comparison to the corresponding vehicle controls there was no  statistically significant or biologically relevant enhancement in the  frequency of the detected micronuclei at any preparation interval and  dose level after administration of the test item. 
The mean values of micronuclei observed after treatment with Sodium Thioglycolate 98%,  Pure were below or near to the value of the vehicle control group.
40 mg/kg b.w. cyclophosphamide administered orally was used as positive  control which showed a statistically significant increase of induced  micronucleus frequency.

Any other information on results incl. tables

Summary of Micronucleus Test Results

test group	dose (mg/kg b.w)	sampling time (h)	PCEs with micronuclei (%)	range	PCE per 2000 erythocytes
vehicle	0	24	0.050	0 - 2	1098
test item	62.5	24	0.060	0 - 2	1124
test item	125	24	0.025	0 - 1	1123
test item	250	24	0.055	0 - 3	1100
Positive control	40	24	1.500	10 -43	1099
test item	250	48	0.095	0 - 6	1123

Historical Controls (1999 – 2004)

	Vehicle Controls			Positive Controls (CPA)
	Males	Females	Total	Males	Females	Total
Mean*±SD	0.078±0.04	0.058±0.033	0.069±0.028	1.867±0.57	1.368±0.497	1.632±0.468
Range**	0.01 - 0.23	0.0 - 0.19	0.01 - 0.15	0.70 -3.46	0.49 -3.55	0.77 - 3.48
No. of Experiments	229	217	230	228	217	229

*: mean value (percent micronucleated cells)

**: range of the mean group values (percent micronucleated cells)

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Sodium Thioglycolate 98%, Pure is considered to be non-mutagenic in this micronucleus assay.

Executive summary:

The clastogenic potential of sodium thioglycolate was evaluated in a micronucleus assay on mouse bone marrow performed according to the OECD guideline # 474. Sodium thioglycolate was administered by single gavage to three groups of five male and five female NMRI mice at dose-levels of 0, 62.5, 125 and 250 mg/kg bw. The positive control was the cyclophosphamide administered orally. The polychromatic erythrocytes/normochromatic erythrocytes ratio (PE/NE) in the treated groups were equivalent to those of the control groups. However, systemic exposure (and thus bone marrow exposure) was confirmed by the clinical signs observed in males and females receiving 250 mg/kg bw of sodium thioglycolate. No increase of the frequency of the micronucleated polychromatic erythrocytes was observed in the bone marrow harvested 24 or 48 hours after the treatment. Positive and vehicle controls gave the expected results.