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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well documented, scientifically sound study that was conducted according to EPA OTS 798.2650 (90-Day Oral Toxicity in Rodents)
Cross-reference
Reason / purpose for cross-reference:
assessment report

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2015
Report date:
2015

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
EPA OTS 798.2650 (90-Day Oral Toxicity in Rodents)
Deviations:
no
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Disodium wolframate
EC Number:
236-743-4
EC Name:
Disodium wolframate
Cas Number:
13472-45-2
Molecular formula:
Na2WO4
IUPAC Name:
disodium dioxotungstenbis(olate)
Test material form:
solid: crystalline
Specific details on test material used for the study:
Sodium tungstate dihydrate (Tungstic acid sodium salt dihydrate, Na2WO42H2O, CAS # 10213-10-2, Batch # 12330JO) 99% pure

Test animals

Species:
rat
Strain:
other: SD
Details on species / strain selection:
5-week-old SD rats were purchased from Charles River laboratories, Raleigh, North Carolina
Sex:
male/female
Details on test animals or test system and environmental conditions:
Animals were held for 1 week in quarantine prior to initiation of treatments. At the start of testing, rats weighed between 199 and 230 g. Test animals were identified by individual cage cards and microchip implants and were individually housed in
polycarbonate cages. Bedding was placed in the bottom of each cage and replaced twice weekly. Drinking quality water and a certified laboratory diet were available ad libitum. Animal rooms were maintained at 64 F to 79 F, with relative humidity of 30% to 70% and a 12-hour light–dark cycle.

Administration / exposure

Route of administration:
oral: drinking water
Details on route of administration:
Sodium tungstate dihydrate was solubilized with DI water to produce 4 dosing solutions
Vehicle:
water
Details on oral exposure:
The dose levels were selected on the basis of our previous studies where the highest dose used was 200 mg/kg/ d in a subchronic toxicity study. Sodium tungstate dihydrate was solubilized with DI water to produce 4 dosing solutions of
200, 125, 75, and 10 mg Na2WO4/mL.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Tungstate concentrations of the dosing solutions were verified by the Aberdeen Test Center and found to be consistent for purity and stability during the study period
Duration of treatment / exposure:
A 90-day oral toxicity study
Frequency of treatment:
Test chemical solutions were administered daily (7 days per week) for 90 days. A 16 GA 2-in stainless steel gavage needle
Doses / concentrationsopen allclose all
Dose / conc.:
10 mg/kg bw/day (actual dose received)
Dose / conc.:
75 mg/kg bw/day (actual dose received)
Dose / conc.:
125 mg/kg bw/day (actual dose received)
Dose / conc.:
200 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
Following 1-week quarantine/acclimatization period, 50 male and 50 female SD rats were randomly distributed
Control animals:
yes, concurrent vehicle
Details on study design:
Sodium tungstate dihydrate was solubilized with DI water to produce 4 dosing solutions of 200, 125, 75, and 10 mg Na2WO4/mL.

Examinations

Observations and examinations performed and frequency:
A clinical examination was made for each animal prior to initiation of treatment and once weekly during treatment. Observations included but were not limited to changes in skin and fur, eyes, mucous membranes, occurrence of secretions and excretions, and autonomic activity (eg, lacrimation, piloerection, pupil size, and unusual respiratory pattern). Changes in gait, posture, and response to handling as well as the presence of clonic or tonic movements, stereotypes (eg, excessive grooming, repetitive circling), or bizarre behavior (eg, selfmutilation, walking backward) were recorded according to testing guidelines. Body and feeder weights were recorded on days .3, .1, 0 (first day of dosing), 7, and weekly thereafter. Doses were adjusted weekly to reflect the change in individual body weights. Animals were observed daily for any toxic signs.
Sacrifice and pathology:
Blood was collected. Each rat was then submitted for complete necropsy. The brain, heart, liver, kidneys, spleen, adrenals, thymus, epididymis/uterus, and testes/ovaries were removed and weighed for absolute organ weights. The tissues harvested for histopathological evaluation included the brain, pituitary, thyroid with parathyroid gland, thymus, lungs, trachea, heart, bone marrow, salivary gland, liver, spleen, kidney, adrenal gland, pancreas, testis, ovaries, uterus, aorta, esophagus, stomach, duodenum, jejunum, ileum, caecum, colon, urinary bladder, salivary lymph node peripheral nerve (siatic), thigh musculature (vastus lateralis), eye, spinal cord (3 levels), and exorbital lachrymal gland.

Hematology parameters included white blood cell count, neutrophils, lymphocytes, monocytes, eosinophils, basophils, red blood cell count, hemoglobin, hematocrit, mean cell volume, mean cell hemoglobin, mean cell hemoglobin concentration, red blood cell distribution width, platelets, and mean platelet volume.

Clinical chemistry parameters measured included The clinical chemistry analytes ialkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, calcium, cholesterol, creatinine kinase, creatinine, glucose (GLU; nonfasting), lactate dehydrogenase, total bilirubin, total protein, triglycerides, Na, K, and Cl

Urinalysis included appearance, pH, specific gravity, GLU, bilirubin, urobilinogen, ketone, blood, protein, nitrite, and leukocytes.
Other examinations:
Ophthalmic examinations were performed on all control and treated animals prior to the scheduled start of the study and within a week of the scheduled 90-day necropsies. Urinalysis was also performed on 8 of 10 animals from all dose
groups (including negative control) within 2 weeks of the final (90-day) necropsies
Statistics:
Food consumption, body weights, and absolute organ weights were compared among dosage groups and controls using ANOVA. When significance was observed, the data were further analyzed using a Dunnett test to compare the doses to the control group. Statistical significance was defined at the P <05 level. Clinical chemistry, hematology, and urinalysis data were analyzed with ANOVA and Bonferroni post hoc test to compare dosage groups to the control group.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Description (incidence and severity):
- No evidence of overt toxicity and no treatment-related clinical signs were seen in any dose levels.
- Results showed that rats dosed with sodium tungstate in water for 90 consecutive days had no abnormal clinical signs at any of the dose levels
Mortality:
mortality observed, non-treatment-related
Description (incidence):
No unscheduled deaths (a single male rat in 200 mg/kg/d dose group was moribund and was euthanized on day 79; a few tissues from this rat were submitted for histopathological examination and death was determined to be not compound related
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
There were significant decreases in food consumption in male rats at 200 mg/kg/d from weeks of 4 to 13, while there was no change in food consumption in female rats during the 90-day study
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
There were significant decreases in food consumption in male rats at 200 mg/kg/d from weeks of 4 to 13, while there was no change in food consumption in female rats during the 90-day study changes in female rats in any dose groups throughout study
period when compared to control rats.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
no effects observed
Description (incidence and severity):
Ophthalmic examinations prior to study initiation and within
a week of the scheduled necropsies revealed no abnormalities
Haematological findings:
no effects observed
Description (incidence and severity):
Male and female rats showed no significant differences in any hematological parameters at any dose levels of sodium tungstate
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
The results of clinical chemistry parameters studied in rats showed no significant changes in any dose levels of sodium tungstate in rats. The parameters studied showed some changes in levels that were not dose related and insignificant and considered within normal range limits when compared to controls. All other parameters were found to be similar to control rats.

Urinalysis findings:
no effects observed
Description (incidence and severity):
Examination of urine samples taken approximately 1 week prior to necropsy revealed no significant changes in volume, specific gravity, or pH. No distinct dose-related trends were observed in GLU, bilirubin, ketone, blood, protein, urobilinogen,
nitrite, or leukocytes
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
The body weights, absolute heart, liver, and thymus weights were significantly lower in male rats dosed at 200 mg/kg/d compared to control rat, but there were no effects on body weights and organ weights of female rats
Gross pathological findings:
not specified
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
- Histopathology examination revealed effects on the urogenital system of the sodium tungstate-treated rats. Changes included mild to severe basophilia of renal cortical tubules in 1 of 9 and 10 of 10 males and 1 of 10 and 8 of 10 females in 2 high-dose
groups (125 and 200 mg/kg/d), respectively.
- Histopathological analysis of epididymides of rats dosed with sodium tungstate showed considerable effects in the high-dose group, Intraluminal cellular debris with and without hypospermia was noted in the epididymides of 3 of 10 males in the 200 mg/kg/d dose group. The lesion was not observed in the 10, 75, and 125 mg/kg/d dose groups.
- Histologic changes were also noted in the glandular stomach of males and females in high dosage groups. The changes included subacute inflammation consisting primarily of EOSs admixed with fewer mononuclear cells observed throughout the submucosa of 5 of 9, 4 of 10 males, and 8 of 10, 9 of 10 females in, 125 and 200 mg/kg/d dosage groups, respectively. Goblet cell metaplasia was also observed in the mucosa of the glandular stomach 8 of 9, 8 of 10 males and 8 of 10, 10 of 10
females of 125 and 200 mg/kg/d dosage groups, respectively. The gastric histologic findings in the lower dosed group were negative when compared to 2 high-dose groups
Histopathological findings: neoplastic:
no effects observed

Effect levels

open allclose all
Key result
Dose descriptor:
BMDL10
Effect level:
102 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
NOAEL
Effect level:
75 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
LOAEL
Effect level:
125 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
LOAEL
Effect level:
175 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
food consumption and compound intake
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
body weight and weight gain
Key result
Dose descriptor:
NOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
clinical signs
haematology
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
histopathology: non-neoplastic

Target system / organ toxicity

Key result
Critical effects observed:
yes
Lowest effective dose / conc.:
125 mg/kg bw/day (actual dose received)
System:
urinary
Organ:
kidney
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
yes

Applicant's summary and conclusion

Conclusions:
Based on histopathology effects seen in the kidneys, the lowest observable adverse effect level was 125 mg/kg/d and the no observable adverse effect level was 75 mg/kg/d in both sexes of rats for oral subchronic toxicity
Executive summary:

Subchronic toxicity of sodium tungstate was assessed in in male and female Sprague-Dawley rats by daily oral gavage of 0, 10, 75, 125, or 200 mg/kg/d for 90 days. There was a significant decrease in food consumption and body weight gain in males at 200 mg/kg/d from days 77 to 90; however, there was no effect in food consumption and body weights in females. There were no changes in the hematological and clinical parameters studied. Histopathological changes were seen in kidney of male and female and epididymis of male rats. Histopathological changes were observed in the kidneys of male and female rats dosed at 125 or 200 mg/k/d consisting of mild to severe cortical tubule basophilia in 2 high-dose groups. Histological changes in epididymides included intraluminal hypospermia with cell debris in the 200 mg/kg/d dosed male rats. Histopathological changes were observed in the glandular stomach including inflammation and metaplasia in the high-dose groups (125 or 200 mg/kg/d) of both sexes of rats. Based on histopathology effects seen in the kidneys, the lowest observable adverse effect level was 125 mg/kg/d and the no observable adverse effect level was 75 mg/kg/d in both sexes of rats for oral subchronic toxicity