(2-hydroxyethyl)ammonium mercaptoacetate

Repeated dose toxicity: dermal

Administrative data

Endpoint:

sub-chronic toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Dec 2002 - Mar 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: According to the standard protocol posted on the NTP website 

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 411 (Subchronic Dermal Toxicity: 90-Day 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

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Sigma Chemical Company (Columbus, OH), lot #88H1166
- Purity, including information on contaminants, isomers, etc.: ca 99%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: stored under a headspace of inert gas at less than or equal to −20°C, protected from light, in amber glass bottles
- Stability and homogeneity of the test material in the vehicle/solvent under test conditions (e.g. in the exposure medium) and during storage: confirmed for at least 10 days

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Administration / exposure

Type of coverage:

open

Vehicle:

other: 95 % Ethanol in deionized water (1:1, v/v)

Details on exposure:

Treatment: After a 10- to 14-day quarantine period, animals are assigned at random  to treatment groups. The study includes five treatment groups each  administered a different concentrations of the test chemicals plus a  control group. Each group contains 10 animals per sex per species. The  animals receive the subject chemical by dermal route of exposure.  Controls receive vehicle alone. Animals are exposed five times per week,  weekdays only, for 90 days after which they are sacrificed with no recovery period. All animals are housed individually. 

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

13 weeks, 24 h/d

Frequency of treatment:

five times per week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

Doses / concentrations 4

Dose / conc.:

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

Doses / concentrations 5

Dose / conc.:

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

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: none

Positive control:

not appropriate

Examinations

Observations and examinations performed and frequency:

BODY WEIGHT: Yes
Animals are weighed individually on day one on test, after seven days,  and at weekly periods thereafter. 

DETAILED CLINICAL OBSERVATIONS: Yes
Animals are observed twice daily, at  least six hours apart (before 10:00 AM and after 2:00 PM), including  holidays and weekends, for moribundity and death. Animals found moribund  or showing clinical signs of pain or distress are humanely euthanized.  Formal clinical observations are performed and recorded weekly. 

HAEMATOLOGY AND CLINICAL CHEMISTRY: Yes
Blood is collected from both sexes of "special study" rats, at days 4 and  22 and from the core study rats at the end of the study. These are  processed for haematology and clinical chemistry determinations. Blood is  collected from core study mice at the end of the study for haematology  determinations.

-Haematology:
Erythrocyte count,  Mean corpuscular volume,  Haemoglobin,  Packed cell volume,  Mean corpuscular haemoglobin,  Mean corpuscular haemoglobin concentration,  Erythrocyte morphologic assessment,  Leukocyte count,  Leukocyte differential,  Reticulocyte count,  Platelet count and morphologic assessment 
-Clinical chemistry:
Sorbitol dehydrogenase (SDH),  Alkaline Phosphatase (ALP),  Creatine Kinase (CK),  Creatinine,  Total Protein,  Albumin,  Urea Nitrogen (BUN),  Total Bile Acids,  Alanine Aminotransferase (ALT)

OTHER:
Sperm Morphology and Vaginal Cytology Evaluations (SMVCE) (see section  7.8.3): SMVCE are conducted on core study rats and mice. Mortality, body weight  changes and clinical signs of toxicity are used to determine the 3 dose  levels used for the SMVCE evaluations.

Sacrifice and pathology:

GROSS PATHOLOGY AND HISTOPATHOLOGY
Organ weights:  Liver, thymus, right kidney, right testis, heart, and lungs weights are  recorded from all animals surviving until the end of the study. 
A complete necropsy is performed on all treated and control animals that  either die or are sacrificed. All tissues required for complete  histopathology are trimmed, embedded, sectioned and stained with  hematoxylin and eosin for histopathologic evaluation.

HISTOPATHOLOGY:
A complete histopathologic evaluation inclusive of gross lesions is done  on all control animals, all animals in the highest dose group with at  least 60% survivors at the time of sacrifice, and all animals in higher  dose groups inclusive of early deaths and survivors. Chemical-related  lesions (target organs) are identified, and these organs plus gross  lesions are examined for all lower doses. Only those tissues designated  as target tissues and gross lesions are evaluated in lower doses to a  no-effect-level. A complete histopathologic evaluation is performed on  all natural death/moribund sacrifice animals in lower dose groups.

Tissues examined histopathologically:  Adrenal glands,  Brain (3 sections including frontal cortex and basal ganglia, parietal  cortex and thalamus, and cerebellum and pons), Clitoral glands,  Esophagus,  Eyes,  Femur, including diaphysis with marrow cavity and epiphysis (femoral  condyle with epiphyseal cartilage plate, articular cartilage and  articular surface),  Gallbladder (mouse),  Gross lesions,  Harderian glands,  Heart and aorta,  Intestine, large (cecum, colon, rectum),  Intestine, small (duodenum, jejunum, ileum), Kidneys,  Liver (2 sections including left lateral lobe and median lobe),  Lungs and mainstem bronchi,  Lymph nodes  - mandibular and mesenteric - inguinal, gluteal, internal iliac (chronic studies only, if lesion  observed, not merely discolouration),  Mammary gland with adjacent skin,  Muscle, thigh (only if neuromuscularsigns were present),  Nasal cavity and nasal turbinates (3 sections),  Ovaries,  Pancreas,  Parathyroid glands,  Pituitary gland,  Preputial glands,  Prostate,  Salivary glands,  Seminal vesicle,  Skin: site of application (topical studies),  Spinal cord and sciatic nerve (if neurologic signs were present),  Spleen, Stomach (forestomach and glandular),  Testes with epididymus,  Thymus,  Thyroid glands,  Tissue masses and regional lymph nodes,  Trachea,  Urinary bladder,  Uterus

Statistics:

yes

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Dermal irritation:

effects observed, treatment-related

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

1.Survival
All Core Study male and female rats survived until terminal sacrifice.

2.Clinical observations
Significant observations noted in both sexes were limited to dermal  irritation at the site of application (SOA), thickened skin at the SOA  and ulcerations at the SOA.
In the males, the incidence of dermal irritation at the SOA was 10/10 for  all five test article treatment groups. Thickening of the skin at the SOA  was observed in 1/10 and 2/10 rats from the 90.0 and 180.0 mg/kg dose  groups, respectively. Ulceration at the SOA was observed in 1/10, 1/10,  5/10 and 8/10 rats from the 11.25, 22.5, 90.0 and 180.0 mg/kg dose  groups, respectively. All other observations noted during the study were  not considered to be biologically significant.
In the females, the incidence of dermal irritation at the SOA was also  10/10 for all five treatment groups. Thickening of the skin at the SOA  was observed in 3/10 rats from the 45.0 mg/kg dose group and in 10/10  rats each from the 90.0 and 180.0 mg/kg dose groups. Ulceration at the  SOA was observed in 10/10 rats from each of the 90.0 and 180.0 mg/kg dose  groups. All other observations noted during the study were not considered  to be biologically significant.

3.Body Weights
Statistical analysis of the Core Study final (terminal) body weights  revealed statistically significant (p<0.05) decreased values in the male  group treated with 90.0 mg/kg when compared to the vehicle control. No  statistically significant differences in body weights were noted for the  female rats when the test article groups were compared to the vehicle  control group.

4.Organ Weights
a.Absolute Organ Weights
The absolute liver weights of the male rats treated with 45.0 mg/kg were significantly (+10%; p<=0.05) increased when compared to the vehicle  control group. There were no other statistically significant differences  in any other absolute organ weights in the male rats. There were no  statistically significant differences in any absolute organ weights in  the female rats.

b.Organ to Body Weight Ratios
The relative kidney and testes weights of the male rats treated with 90.0  (+7.6% and 6.7%, respectively) and 180.0 mg/kg (+8.2 and 7.6%,  respectively) were significantly (p<=0.05) increased when compared to the  vehicle control group. The relative liver weights for the male rats  treated with 45.0 mg/kg were significantly (+8.5%; p<=0.05) increased  when compared to the vehicle control group. The relative spleen weights  of the male rats treated with 90.0 mg/kg were significantly (+6.0%;  p<=0.05) increased when compared to the vehicle control group. The  relative kidney weights of the female rats treated with 180.0 mg/kg were  significantly (+6.6%; p<=0.05) increased when compared to the vehicle  control group. The relative thyroid/parathyroid weights of the female  rats treated with 22.5 mg/kg were significantly (-20%; p<=0.05) decreased  when compared to the vehicle control group. There were no other  statistically significant differences in any relative organ weight for  the male or female rats.

5.Clinical Pathology
There were limited statistically significant (p<0.05) differences in the  chemistry and haematology results when compared to the control group, but  these were not dose responsive nor considered to be biologically  significant.

6.Anatomic Pathology
a.Gross Lesions
For the males, abnormal gross necropsy findings were limited to skin  accumulation (no mass noted) at the SOA in 1/10 rats from the 11.25, 45.0  and 180.0 mg/kg dose groups, a nodule on the thoracic inlet of the  thoracic cavity in 1/10 rats from both the 11.25 and 22.5 mg/kg dose  groups, a mass on the median lobe of the liver in 1/10 rats from the  180.0 mg/kg dose group and a nodule on the liver in 1/10 rats from the  22.5 mg/kg dose group. In addition, one male from the 180.0 mg/kg dose  group had retained the right testis in its abdominal region. There were  no other significant abnormal gross lesions noted in any of the male  treatment groups. These findings were not considered to be test article  related or biologically significant.
For the females, abnormal gross necropsy findings were limited in number.  In the vehicle control group, one female rat was noted as having a focus  on the left kidney. In the 11.25 mg/kg test article treatment group, four  females were noted as having a nodule on the liver, one with a nodule on  the pancreas, one rat with a nodule on the thoracic cavity and one rat  with dilated uterine horns: One rat from the 22.5 mg/kg dose group had a  cyst on the left ovary. There were two and three rats from the 45.0 and  90.0 mg/kg treatment groups, respectively, noted as having a nodule on  the liver. In the high dose treatment group (180.0 mg/kg), there were two  animals with nodules on the liver, two animals with nodules in the  thoracic cavity, one rat with enlarged mediastinal lymph nodes and one  rat with dilated uterine horns. These findings were not considered to be  test article related or biologically significant. Findings which may be  contributed to the treatment of NaT were limited to the 180.0 mg/kg  treatment group where three rats were noted as having an irritation on  the SOA.

b.Microscopic Pathology Repeated dermal administration of Sodium Thioglycolate (NaT) for thirteen  weeks (excluding weekends) resulted in test article related microscopic  changes at the site of application (SOA) in both male and female rats at  all treatment doses. Changes in the skin SOA revealed minimal to mild  hyperplasia of the epidermis accompanied, in many animals, by sebaceous  gland hyperplasia and hyperkeratosis. The severity of the changes was  comparable between all treatment groups in both the male and female rats.  A NOEL was not reached in female or male rats.

Microscopic evaluation of the other tissues required by the protocol  revealed a few findings which were observed either in small numbers  and/or in both control and treated animals. And, all of these changes are  commonly observed in F344 rats. For these reasons, these changes were  considered incidental findings.
[NOTE: The pathologist used the following criteria for severity scoring  of the epidermal hyperplasia; minimal 2-3 cell layers thick, mild 4-6  cell layers thick, moderate 7-8 cell layers thick and marked >9 cell  layers thick (at the thickest point).]

Effect levels

1

Key result

Dose descriptor:

NOAEL

Remarks:

systemic toxicity

Effect level:

>= 180 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

2

Key result

Dose descriptor:

LOAEL

Remarks:

Local effects

Effect level:

11.25 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

dermal irritation

Target system / organ toxicity

Key result

Critical effects observed:

no

Any other information on results incl. tables

Female rats organ weight summary table

Dose Group (mg/kg)

Body Wt (Sac)(g)

Heart Wt (g)

%Heart/Body

Liver Wt (g)

%Liver/Body

Lung Wt (g)

%Lungs/Body

R Kidney Wt (g)

%R Kidney/Body

Spleen Wt (g)

%Spleen/Body

Thyroid Wt (g)

%Thyroid/Body

Day 93

0

177.3 ± 2.98

0.65 ± 0.013

0.37 ± 0.004

5.60 ± 0.173

3.16 ± 0.068

1.053 ± 0.0289

0.59 ± 0.008

0.70 ± 0.014

0.392 ± 0.0041

0.44 ± 0.007

0.25 ± 0.002

0.026 ± 0.0009

0.014 ± 0.0006

11.25

185.4 ± 2.56

0.65 ± 0.016

0.35 ± 0.005

5.59 ± 0.123

3.01 ± 0.048

1.001 ± 0.0427

0.54 ± 0.020

0.73 ± 0.009

0.391 ± 0.0025

0.45 ± 0.009

0.24 ± 0.004

0.026 ± 0.0010

0.014 ± 0.0006

22.5

184.5 ± 2.74

0.66 ± 0.008

0.36 ± 0.007

6.04 ± 0.156

3.27 ± 0.057

0.978 ± 0.0219

0.53 ± 0.010

0.72 ± 0.010

0.389 ± 0.0044

0.44 ± 0.006

0.24 ± 0.004

0.023 ± 0.0007

0.012 ± 0.0004

45

185.9 ± 2.75

0.65 ± 0.011

0.35 ± 0.004

5.90 ± 0.153

3.17 ± 0.048

1.101 ± 0.0468

0.59 ± 0.027

0.72 ± 0.020

0.389 ± 0.0086

0.45 ± 0.012

0.24 ± 0.005

0.024 ± 0.0013

0.013 ± 0.0007

90

179.9 ± 3.54

0.67 ± 0.016

0.37 ± 0.008

5.94 ± 0.141

3.31 ± 0.066

1.059 ± 0.0414

0.59 ± 0.018

0.75 ± 0.021

0.415 ± 0.0090

0.44 ± 0.012

0.25 ± 0.007

0.026 ± 0.0009

Organ Weights Summary Table in male rats

(Mean ± SEM)

Dose Group (mg/kg)

Body Wt (Sac)(g)

Heart Wt (g)

%Heart/Body

Liver Wt (g)

%Liver/Body

Lung Wt (g)

%Lungs/Body

R Kidney Wt (g)

%R Kidney/Body

R Testis Wt (g)

%R Testis/Body

Spleen Wt (g)

%Spleen/Body

Thyroid Wt (g)

%Thyroid/Body

Day 93

0

334.5 ± 3.86

0.97 ± 0.014

0.29 ± 0.003

11.22 ± 0.270

3.35 ± 0.048

1.532 ± 0.0627

0.46 ± 0.019

1.14 ± 0.021

0.340 ± 0.0044

1.442 ± 0.0248

0.432 ± 0.0089

0.72 ± 0.010

0.21 ± 0.002

0.026 ± 0.0015

0.008 ± 0.0004

11.25

333.7 ± 4.16

0.98 ± 0.022

0.29 ± 0.005

11.90 ± 0.264

3.57 ± 0.062

1.502 ± 0.0512

0.45 ± 0.014

1.20 ± 0.026

0.359 ± 0.0065

1.468 ± 0.0227

0.440 ± 0.0042

0.72 ± 0.012

0.21 ± 0.003

0.026 ± 0.0010

0.008 ± 0.0004

22.5

332.0 ± 7.07

0.95 ± 0.018

0.29 ± 0.004

11.71 ± 0.341

3.52 ± 0.062

1.541 ± 0.0849

0.46 ± 0.019

1.17 ± 0.024

0.352 ± 0.0054

1.386 ± 0.0247

0.418 ± 0.0075

0.72 ± 0.017

0.22 ± 0.004

0.027 ± 0.0011

0.008 ± 0.0004

45

339.4 ± 4.77

0.97 ± 0.010

0.29 ± 0.003

12.36 ± 0.292

3.64 ± 0.046

1.518 ± 0.0535

0.45 ± 0.016

1.18 ± 0.019

0.348 ± 0.0053

1.419 ± 0.0286

0.418 ± 0.0067

0.72 ± 0.016

0.21 ± 0.003

0.030 ± 0.0049

0.009 ± 0.0014

90

312.1 ± 8.54

0.95 ± 0.023

0.31 ± 0.005

10.46 ± 0.349

3.35 ± 0.074

1.451 ± 0.0448

0.47 ± 0.012

1.14 ± 0.023

0.366 ± 0.0041

1.435 ± 0.0300

0.461 ± 0.0082

0.71 ± 0.016

0.23 ± 0.004

0.028 ± 0.0018

0.009 ± 0.0007

180

319.3 ± 5.89

0.93 ± 0.019

0.29 ± 0.004

11.26 ± 0.261

3.53 ± 0.066

1.497 ± 0.0268

0.47 ± 0.008

1.17 ± 0.024

0.368 ± 0.0048

1.482 ± 0.0282

0.465 ± 0.0081

0.72 ± 0.016

0.23 ± 0.003

0.027 ± 0.0011

0.008 ± 0.0004

Hematology Summary Table in male rats

(Mean ± SEM)

Dose Group (mg/kg)

Erythrcyt (10^6/uL)

Hgb (g/dL)

HCT (Automated) (%)

MCV (fL)

MCH (pg)

MCHC (g/dL)

Retics (10^6/uL)

Platelet (10^3/uL)

Leukocytes (10^3/uL)

Neut (10^3/uL)

Lymph (10^3/uL)

Mono (10^3/uL)

EOS (10^3/uL)

Basophils (10^3/uL)

Day 4

0

6.79 ± 0.115

13.40 ± 0.228

40.3 ± 0.70

59.25 ± 0.250

19.71 ± 0.058

33.25 ± 0.033

6.790 ± 6.3157

594.38 ± 26.679

10.613 ± 0.6269

1.18 ± 0.065

8.550 ± 0.5125

0.645 ± 0.0619

0.034 ± 0.0032

0.228 ± 0.0272

11.25

6.87 ± 0.099

13.53 ± 0.175

40.8 ± 0.53

59.44 ± 0.294

19.72 ± 0.101

33.18 ± 0.086

0.540 ± 0.0181

560.00 ± 39.746

9.267 ± 0.5191

1.03 ± 0.084

7.437 ± 0.3901

0.580 ± 0.0488

0.022 ± 0.0036

0.189 ± 0.0182

22.5

6.70 ± 0.062

13.18 ± 0.122

39.7 ± 0.39

59.22 ± 0.324

19.64 ± 0.053

33.21 ± 0.090

0.526 ± 0.0253

530.56 ± 25.532

10.133 ± 0.4269

1.17 ± 0.075

8.011 ± 0.4151

0.614 ± 0.0411

0.047 ± 0.0231

0.289 ± 0.0648

45

6.75 ± 0.088

13.21 ± 0.193

39.7 ± 0.55

58.78 ± 0.222

19.58 ± 0.092

33.23 ± 0.078

0.526 ± 0.0233

591.00 ± 15.200

9.467 ± 0.4304

1.05 ± 0.053

7.679 ± 0.3323

0.550 ± 0.0610

0.027 ± 0.0041

0.183 ± 0.0213

90

6.62 ± 0.131

12.99 ± 0.231

39.1 ± 0.74

59.11 ± 0.200

19.64 ± 0.071

33.28 ± 0.072

0.454 ± 0.0250

561.78 ± 30.219

10.333 ± 0.6727

1.13 ± 0.068

8.326 ± 0.5376

0.620 ± 0.0624

0.032 ± 0.0066

0.224 ± 0.0306

180

6.90 ± 0.127

13.55 ± 0.257

41.0 ± 0.76

59.38 ± 0.183

19.68 ± 0.067

33.15 ± 0.060

0.528 ± 0.0228

569.50 ± 29.019

10.788 ± 0.4951

1.33 ± 0.189

8.556 ± 0.4194

0.689 ± 0.0282

0.025 ± 0.0038

0.203 ± 0.0230

Day 22

0

7.71 ± 0.209

15.18 ± 0.393

45.6 ± 1.20

59.11 ± 0.200

19.72 ± 0.060

33.32 ± 0.064

0.297 ± 0.0262

522.44 ± 36.472

15.089 ± 2.0608

1.27 ± 0.142

12.442 ± 1.7536

0.987 ± 0.1496

0.048 ± 0.0092

0.323 ± 0.0401

11.25

7.42 ± 0.086

14.63 ± 0.169

43.9 ± 0.53

59.20 ± 0.200

19.73 ± 0.091

33.34 ± 0.079

0.307 ± 0.0153

563.70 ± 18.524

15.520 ± 3.0618

1.47 ± 0.262

12.694 ± 2.5321

0.905 ± 0.2006

0.059 ± 0.0109

0.390 ± 0.0828

22.5

7.45 ± 0.151

14.68 ± 0.286

44.1 ± 0.91

58.90 ± 0.180

19.72 ± 0.053

33.36 ± 0.083

0.278 ± 0.0182

534.10 ± 31.043

18.050 ± 3.1819

1.60 ± 0.247

14.848 ± 2.6952

1.090 ± 0.1804

0.073 ± 0.0133

0.456 ± 0.0953

45

7.45 ± 0.082

14.72 ± 0.113

44.2 ± 0.36

59.30 ± 0.213

19.78 ± 0.088

33.36 ± 0.072

0.318 ± 0.0104

512.30 ± 20.314

16.740 ± 4.6934

1.61 ± 0.472

13.853 ± 4.0386

0.785 ± 0.1583

0.059 ± 0.0135

0.443 ± 0.1542

90

7.54 ± 0.108

14.87 ± 0.192

44.6 ± 0.56

59.30 ± 0.153

19.73 ± 0.075

33.37 ± 0.079

0.301 ± 0.0120

545.30 ± 14.062

14.410 ± 2.2688

1.42 ± 0.206

11.944 ± 1.9392

0.714 ± 0.0967

0.056 ± 0.0120

0.287 ± 0.0404

180

7.38 ± 0.103

14.58 ± 0.208

43.8 ± 0.64

59.30 ± 0.213

19.78 ± 0.090

33.32 ± 0.076

0.301 ± 0.0197

519.00 ± 17.491

16.770 ± 3.2436

1.47 ± 0.265

14.046 ± 2.7995

0.885 ± 0.1514

0.039 ± 0.0071

0.346 ± 0.0533

Day 93

0

9.13 ± 0.056

15.66 ± 0.130

45.3 ± 0.34

49.70 ± 0.213

17.17 ± 0.062

34.54 ± 0.078

0.200 ± 0.0114

511.60 ± 13.123

10.910 ± 0.3854

2.88 ± 0.178

7.087 ± 0.2720

0.591 ± 0.0522

0.122 ± 0.0087

0.228 ± 0.0256

11.25

9.10 ± 0.105

15.62 ± 0.197

45.1 ± 0.55

49.40 ± 0.163

17.18 ± 0.057

34.64 ± 0.075

0.216 ± 0.0170

503.60 ± 12.751

11.080 ± 0.3797

3.03 ± 0.211

6.865 ± 0.3349

0.739 ± 0.0562

0.148 ± 0.0061

0.288 ± 0.0179

22.5

9.19 ± 0.116

15.83 ± 0.205

45.8 ± 0.56

49.90 ± 0.180

17.26 ± 0.058

34.56 ± 0.109

0.221 ± 0.0067

518.30 ± 13.856

10.600 ± 0.4487

2.57 ± 0.221

7.083 ± 0.3183

0.602 ± 0.0525

0.117 ± 0.0118

0.222 ± 0.0224

45

9.04 ± 0.107

15.45 ± 0.194

44.6 ± 0.55

49.30 ± 0.153

17.08 ± 0.049

34.60 ± 0.058

0.211 ± 0.0087

525.50 ± 12.172

10.990 ± 0.5098

2.76 ± 0.138

7.203 ± 0.3873

0.610 ± 0.0577

0.141 ± 0.0219

0.295 ± 0.0668

90

9.26 ± 0.083

15.90 ± 0.146

46.1 ± 0.44

50.00 ± 0.149

17.16 ± 0.054

34.46 ± 0.076

0.232 ± 0.0125

524.80 ± 15.867

10.770 ± 0.3821

2.98 ± 0.139

6.784 ± 0.2742

0.606 ± 0.0611

0.132 ± 0.0178

0.259 ± 0.0316

180

9.15 ± 0.081

15.79 ± 0.148

45.4 ± 0.44

49.70 ± 0.153

17.24 ± 0.062

34.73 ± 0.088

0.209 ± 0.0077

502.90 ± 13.825

9.750 ± 0.4143

2.19 ± 0.191

6.769 ± 0.3326

0.474 ± 0.0309

0.097 ± 0.0070

0.209 ± 0.0247

Abbreviations:

NA: Not Available,SEM: Standard Error of Means,V: Vehicle Control,Erythrcyt: Erythrocytes,Hgb: Hemoglobin,HCT: Hematocrit,MCV: Mean Corpuscular Volume,MCH: Mean Corpuscular Hemoglobin,MCHC: Mean Corpuscular Hemoglobin Concentration,Retics: Reticulocytes,Platelet: Platelets,Leukocytes: Leukocytes,Neut: Neutrophils,Lymph: Lymphocytes,Mono: Monocytes,EOS: Eosinophils,Basophils: Basophils, CL = Sample clotted

Applicant's summary and conclusion

Conclusions:

The Lowest-Observed-Effect-Level (LOEL) at the application site was 11.25 mg/kg based on histopathologic examination. There was no No-Observed-Effect-Level (NOEL) at the application site.
The NOAEL for systemic toxicity can be estimated to be higher than 180 mg/kg bw/d.

Executive summary:

The potential subchronic dermal toxicity of sodium mercaptoacetate was evaluated according to a NTP protocol. Sodium mercaptoacetate was applied once daily in Sprague-Dawley rats (10 Males and 10 Females) skin, at the dose-levels of 11.25, 22.5, 45.0, 90.0, and 180.0  mg/kg bw/d during 90 days, 5 days a week. A control group was tested with vehicle (ethanol in water). No satellite group was tested for reversibility or persistence occurrence of toxic effects.

Body weights were recorded on day one on test, weekly and prior necropsy. Animals were observed twice daily for morbidity and mortality. Blood was collected from both sexes of "special study" rats, at days 4 and 22 and from the core study rats at the end of the study. These was processed for haematology and clinical chemistry determinations. Blood was collected from core study mice at the end of the study for haematology determinations. All animals were examined for gross pathology, and organs were weighted and submitted to histopathology.

No death were reported in any treated group. Significant observations noted in both sexes were limited to dermal irritation at the site of application (SOA), thickened skin at the SOA and ulcerations at the SOA. There were only limited statistically significant differences in the body weight, organ weight, chemistry and haematology results. No gross lesions finding were considered to be test article related or biologically significant. Repeated dermal administration of Sodium Thioglycolate (NaTG) for thirteen weeks (excluding weekends) resulted in test article related microscopic changes at the site of application (SOA) in both male and female rats at all treatment doses. Changes in the skin SOA revealed minimal to mild hyperplasia of the epidermis accompanied, in many animals, by sebaceous gland hyperplasia and hyperkeratosis. The severity of the changes was comparable between all treatment groups in both the male and female rats.

The Lowest-Observed-Effect-Level (LOEL) at the application site was 11.25 mg/kg based on histopathologic examination. There was no No-Observed-Effect-Level (NOEL) at the application site. The NOAEL for systemic toxicity can be estimated to be higher than 180 mg/kg bw/d.