(2-hydroxyethyl)ammonium mercaptoacetate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

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 1

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Reference 2

Reference Type:

publication

Title:

Developmental Toxicity Evaluation of Sodium Thioglycolate Administered Topically to Sprague-Dawley (CD) Rats and New Zealand White Rabbits

Author:

Tyl RW, Price CJ, Marr MC, Myers BB, van Birgelen APJM and Jahnke GD

Year:

2003

Bibliographic source:

Birth Defects Research (Part B) 68:144-161

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

no

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 substance: Sodium thioglycolate
CAS No.: 367-51-1
Source: Sigma Chemical Company by Midwest Research Institute (Kansas City, MO)
Batch: No. 88H1166
Purity: 99% (identity confirmed by infrared spectrometry) Solvent: 95% ethanol:distilled water (1:1).

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

Test animals:         
- Source: Charles River Laboratories (Raleigh, NC).        
- Age: no data         
- Weight at dosing: ca. 250 g        
-  Acclimation period: no data        
- Diet: Purina Certified Rodent Chow (No. 5002), ad libitum        
-  Water: Tap water, ad libitum         
- Housing: singly housed in solid-bottom  polycarbonate cages with stainless steel wire lids with Sani-Chips certified hardwood bedding

Environmental conditions:         
- Temperature: 70.0-72.81 F         
- Humidity: 28.0-58 %         
- Air changes: no data         
- Photoperiod: Alternating 12-hour light and dark cycles

Administration / exposure

Route of administration:

dermal

Vehicle:

other: 95% ethanol:distilled water, 1:1

Details on exposure:

Treatment: 1.5 ml/kg of test material in vehicle or vehicle alone was applied  directly to a 3x3 inch shaved area on the dorsum of the rat with a glass  syringe fitted with a 16-gauge, stainless-steel, ball-tipped dosing  needle. The formulation was allowed to remain on the animal for a minimum  of 6 hr/treatment day. At the end of each 6-hr period, the application  site was wiped with warmwater-soaked gauze to remove residual vehicle or  sodium thioglycolate.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Prepared weekly based on stability information and were verified to be  within 92.7-103.5 % of target.

Duration of treatment / exposure:

gestation days 6-19

Frequency of treatment:

daily

Duration of test:

necropsy on GD 20

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

200 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

Pregnant Sprague Dawley derived (CD.) rats were topically exposed to sodium thioglycolate in vehicle (50, 100, and 200 mg/kg/day) or vehicle  alone (95% ethanol:distilled water, 1:1) from gestational day (gd) 6  through 19.

Examinations

Maternal examinations:

Females were monitored at regular intervals throughout gestation for clinical signs (including dosing site condition), feed and water intake, and body weight. At necropsy on GD 20, the following were recorded: maternal clinical condition; body, liver and gravid uterine weights; and pregnancy status.

Ovaries and uterine content:

The number of ovarian corpora lutea and uterine implantations (resorbed,  dead, or live fetuses) was recorded.

Fetal examinations:

All live foetuses were counted, weighed, and examined for external alterations, including cleft palate. Approximately 50% of the live foetuses per litter were sexed internally  and examined for visceral alterations. These foetuses were decapitated  and the heads fixed, decalcified, and examined for soft tissue  craniofacial alterations. All foetal carcasses were eviscerated (and  foetuses not scheduled for a visceral examination were sexed internally),  macerated, and stained with alizarin red S and alcian blue. Intact  foetuses (those not decapitated) were examined for ossified and  cartilaginous skeletal alterations.

Statistics:

The unit for statistical measurement was the pregnant female or the  litter. Quantitative continuous data (e.g., maternal body weights, foetal  body weights, feed consumption, etc.) were compared among treatment  groups, per species, by parametric statistical tests whenever Bartlett  test for homogeneity of variance was not significant.  General linear models (GLM) procedures were applied to the ANOVA and the  tests for linear trend. Before GLM analysis, an arc sine-square root  transformation was carried out on all litter-derived percentage data  (e.g., % resorptions/litter, % malformations/litter, % variations/litter)  (Snedecor and Cochran, 1967). For litter-derived percentage data, the  ANOVA was weighted according to litter size. When a significant (p <  0.05) main effect for dose occurred, Dunnett's multiple comparison test  (Dunnett, 1955, 1964) was used to compare each treatment group to the  control group for that measure. A one-tailed (i.e., Dunnett's test) was used for all pairwise comparisons  to the vehicle control group, except that a two-tailed test was used for maternal body and organ weight  parameters, maternal feed consumption, fetal body weight, and percent  males per litter.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

effects observed, treatment-related

Description (incidence and severity):

see below

Mortality:

mortality observed, treatment-related

Description (incidence):

see below

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

see below

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

see below

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

effects observed, treatment-related

Description (incidence and severity):

see below

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not specified

Details on results:

Sodium thioglycolate treatment was associated with one maternal death at 200 mg/kg/day (only clinical observations at the dosing site preceded death). Other effects, dependent on dose and exposure duration, included body weight and weight gain reductions, changes in relative feed and water intake, and discolouration and slight erythema at the application site. Feed consumption in g/kg/day was significantly increased above the control at 50 (5.4%) and 100 (6.1%) mg/kg/day, but not at 200 mg/kg/day (2.2%). Maternal water consumption in g/kg/day was significantly increased at 200 mg/kg/day, (12.7%) and slightly (but not statistically significantly) increased at 50 (3.2%) and 100 (5.1%) mg/kg/day. Maternal body weights and body weight changes were decreased only at 200 mg/kg/day. At scheduled necropsy, there were no macroscopic indications of organ toxicity. In addition, organ weights and gravid uterine weights were equivalent across groups; maternal body weight was significantly reduced at 200 mg/kg/day.

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Effect levels (maternal animals)

1

Key result

Dose descriptor:

NOAEL

Effect level:

< 50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

clinical signs

food consumption and compound intake

2

Key result

Dose descriptor:

LOAEL

Effect level:

<= 50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

clinical signs

food consumption and compound intake

Maternal abnormalities

Key result

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

see below

Reduction in number of live offspring:

effects observed, treatment-related

Description (incidence and severity):

see below

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

effects observed, treatment-related

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Visceral malformations:

no effects observed

Other effects:

not specified

Details on embryotoxic / teratogenic effects:

Details on embryotoxic / teratogenic effects:
Prenatal viability was unaffected by maternal exposure to sodium  thioglycolate. The incidences of foetal external, visceral, and skeletal  alterations were also unaffected. A significant, dose-related, upward  trend was present for % foetuses with skeletal variations per litter, but  there were no significant pairwise comparisons to the vehicle control  group value. The historical data presented in the study report shown a  range of 0.58 to 25.65 % for this parameter, with 9 out of 21 studies  (43%) with a % higher than 15.1% (the highest value observed at 200 mg/kg  bw/d). Accordingly, this effect was not considered as treatment-related.  Body weights of male and female foetuses per litter at 200 mg/kg/day were  significantly lower than control values.

Effect levels (fetuses)

1

Key result

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reduction in number of live offspring

fetal/pup body weight changes

changes in litter size and weights

2

Key result

Dose descriptor:

LOAEL

Effect level:

200 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reduction in number of live offspring

fetal/pup body weight changes

changes in litter size and weights

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Any other information on results incl. tables

Maternal Toxicity in CD Rats Exposed to Sodium Thioglycolate by Topical Application on Gestational Days 6 Through 19

                                              

	Sodium thioglycolate (mg/kg/day, dermal)
	0	50	100	200
Maternal pregnancy status
Treated, n	25	25	25	25
Removed, n	0	0	0	0
Dead or euthanized, n	0	0	0	1a
Pregnant at sacrifice, n(%)	25(100)	23(92)	23(92)	21(88)b
Maternal body weight changes (g)c,d
Pretreatment wt. gain (GD 0–6)	32.2±1.3h	29.21±1	28.4±2.1	26.5±1.6
Gestation weight gain (GD 0–20)	135.6±3.3i	129.7±4.4	127.0±5.0	112.5±5.9k
Treatment weight gain (GD 6–20)	110.1±3.1i	106.5±4.0	104.8±3.8	92.7±5.7j
Corrected weight gaine	49.6±1.8i	45.6±2.4	43.9±3.3	34.8±2.8k
Gravid uterine wt.	86.0±3.2	84.1±3.1	83.0±3.1	77.6±4.9
Maternal organ weightsc,f
Liver Absolute (g)	17.78±0.23	17.64±0.40	17.69v0.29	17.02±0.27
Relative (% sacrifice wt.)f	4.53±0.04	4.56±0.07	4.62±0.05	4.65±0.08
Kidney Absolute (g)	2.22±0.04	2.19±0.05	2.26±0.05	2.20±0.04
Relative (% sacrifice wt.)f	0.57±0.01h	0.57±0.01	0.59±0.01	0.60±70.01
Maternal feed consumptionc,g
Pretreatment period (gd 0–6)
Absolute (g/day)	23.4±0.5	23.2±0.6	22.6±0.6	22.5±0.4
Relative (g/kg/day)	85.0±1.4	84.6±1.7	83.3±2.0	83.6±1.3
Treatment period (GD 6–20)
Absolute (g/day)	26.3±0.3	27.5±0.4	27.3±0.5	25.5±0.4
Relative (g/kg/day)	77.1±0.5	81.3±0.9k	81.8±0.8k	78.8±0.8
Maternal water consumptionc,g
Pretreatment period (gd 0–6)
Absolute (g/day)	35.7±1.2	34.2±0.9	32.4±1.1	34.1±0.9
Relative (g/kg/day)	129.8v4.3	125.2v2.9	119.0±3.5	126.9±3.1
Treatment period (gd 6–20)
Absolute (g/day)	43.6±1.3	44.1±1.3	44.4±1.1	46.2±1.2
Relative (g/kg/day)	127.1±3.2i	131.2±3.3	133.6±2.6	143.3v3.9k

aDam 4 was found dead on the morning of gd 18.

bDam 31 had only one implantation site, and no live fetuses on gd 20.

cIncludes all dams pregnant at sacrifice; mean 7 SEM; gd, gestational day.

dBody weights were recorded in the morning of each designated gestational day.

eWeight change during gestation minus gravid uterine weight.

fCalculated using body weight at the time of sacrifice on gd 20.

gRelative feed and water consumption (g/kg/day) were calculated using appropriate body weights.

hp<0.05; Test for linear trend.

ip<0.01; Test for linear trend.

jp<0.05; Dunnett’s test

k p<0.01; Dunnett’s test.

Developmental Toxicity in CDsRat Fetuses Following Maternal Exposure to Sodium Thioglycolate by Topical. Application on Gestational Days 6 Through 19

	Sodium Thioglycolate (mg/kg/day, dermal)
	0	50	100	200
All littersa,b	25	23	23	21
No. corpora lutea/dam	17.5±0.4	16.7±0.5	16.4±0.5	16.8±0.7
No. implantation sites/litter	15.6±0.5	15.1±0.6	14.7±0.7	15.4±v0.8
% preimplantation loss/litter	11.2±2.7	10.3±2.4	11.6±3.6	10.5±4.1
% resorptions/litter	3.9±1.3	4.6±1.4	3.0±0.9	11.2±5.1
% litters with resorptions	40	48	35	52
% late fetal deaths/litter	0.0±0.0	0.3±0.3	0.0±0.0	0.0±0.0
% litters with late fetal deaths	0	4	0	0
Live littersb,c	25	23	23	20d
No. live fetuses/litter	15.0±0.6	14.4±0.6	14.2±0.6	15.1±0.6
Avg. male fetal body wt./litter (g)	3.73±0.06f	3.70±0.05	3.75±0.08	3.42±0.08g
Avg. female fetal body wt./litter (g)	3.50±0.05e	3.56±0.05	3.61±0.10	3.2570.08g
% male fetuses/litter	45.173.6	52.373.5	50.673.2	52.5±2.3
% externally malformed fetuses/litter	0.0±0.0	0.0±0.0	0.9±0.7	0.3±0.3
% viscerally malformed fetuses/litter	0.0±0.0	0.5±0.5	0.0±0.0	2.2±1.7
% skeletally malformed fetuses/litter	2.3±1.8	2.2±1.0	1.2±0.8	4.5±2.6
% malformed fetuses/litter	1.1±0.9	1.4±0.6	1.5±0.7	3.4±2.2
% fetuses with external variations/litter	0.5±0.5	0.5±0.4	0.0±0.0	0.3±0.3
% fetuses with visceral variations/litter	3.3±1.3	5.0±1.5	3.7±1.7	3.7±2.2
% fetuses with skeletal variations/litter	3.9±1.3f	6.4±2.3	11.2±3.0	15.1±4.2
% fetuses with variations/litter	4.1±1.0	6.3±1.4	7.3±1.7	9.9±2.6

aIncludes all dams pregnant at sacrifice; litter size¼no. implantation sites per dam.

bReported as the mean 7 SEM.

cIncludes only dams with live fetuses; litter size¼no. live fetuses per dam.

dOne female at 200 mg/kg/day had a fully resorbed litter at scheduled necropsy.

ep<0.05; Test for linear trend.

fp<0.01; Test for linear trend.

gp<0.05; Dunnett’s test.

Applicant's summary and conclusion

Conclusions:

Topically applied sodium thioglycolate resulted in toxicity to the dam at 200 mg/kg/day (expressed as reduced body weights and weight gain, increased relative water consumption, observations at the dosing site and one death). Treatment-related increases in feed consumption (and observations at the application site) were also present at 50 and 100 mg/kg/day, in the absence of increased body weights or body weight change. This is an uncommon finding and has been previously observed in rats exposed to sodium thioglycolate, attributed to a block in fatty acid metabolism. Sodium thioglycolate at 200 mg/kg/day also resulted in significantly decreased male and female foetal body weights per litter, with no other evidence of embryofoetal toxicity and no evidence of treatment-related teratogenicity. Based on the study findings, a no observed adverse effect level (NOAEL) could not be identified for maternal toxicity while for developmental toxicity, 100 mg/kg/day was the NOAEL.

Executive summary:

The developmental toxicity of sodium thioglycolate was evaluated in pregnant rats in a study performed according to a method comparable to the OECD guideline # 414. Pregnant Sprague-Dawley rats were exposed topically, 6 hr/day, to sodium thioglycolate (99% pure) in vehicle (95% ethanol:distilled water, 1:1) from gestational day (gd) 6 through 19 at dose levels of 0, 50, 100, and 200 mg/kg bw/d. Twenty-five timed-mated female rats were assigned to each group and monitored at regular intervals throughout gestation for clinical signs (including dosing site condition), feed and water intake, and body weight. At necropsy on gestational day 20; the following were recorded: maternal clinical condition; body, liver and gravid uterine weights; and pregnancy status. The number of ovarian corpora lutea and uterine implantations (resorbed, dead, or live foetuses) was recorded. All live foetuses were counted, weighed, and examined for external alterations, including cleft palate. Approximately 50% of the live rat foetuses per litter were sexed internally and examined for visceral alterations. These foetuses were decapitated and the heads fixed, decalcified, and examined for soft tissue craniofacial alterations. All foetal carcasses were eviscerated (and rat foetuses not scheduled for a visceral examination were sexed internally), macerated, and stained with alizarin red S and alcian blue. Intact rat foetuses (those not decapitated) were examined for ossified and cartilaginous skeletal alterations.

Sodium thioglycolate treatment was associated with one maternal death at 200 mg/kg/d (only clinical observations at the dosing site preceded death). Other effects, dependent on dose and exposure duration, included body weight and weight gain reductions, changes in relative feed and water intake, and discoloration and slight erythema at the application site. Feed consumption was significantly increased above the control at 50 (5.4%) and 100 (6.1%) mg/kg bw/d, but not at 200 mg/kg bw/d (2.2%). Maternal water consumption was significantly increased at 200 mg/kg bw/d (12.7%) and slightly (but not statistically significantly) increased at 50 (3.2%) and 100 (5.1%) mg/kg bw/d. Maternal body weights and body weight changes were decreased only at 200 mg/kg bw/d. At scheduled necropsy, there were no macroscopic indications of organ toxicity. In addition, organ weights and gravid uterine weights were equivalent across groups; maternal body weight was significantly reduced at 200 mg/kg/d. Prenatal viability was unaffected by maternal exposure to sodium thioglycolate. The incidences of foetal external, visceral, and skeletal alterations were also unaffected. A significant, dose-related, upward trend was present for % foetuses with skeletal variations per litter, but there were no significant pairwise comparisons to the vehicle control group value and the % were in the range of the historical control data . Body weights of male and female foetuses per litter at 200 mg/kg bw/d were significantly lower than control values. The maternal NOAEL could not be identified.