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Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
no data available
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented publication

Data source

Reference
Reference Type:
publication
Title:
Oral toxicity of bismuth in rat: Single and 28-day repeated administration studies.
Author:
Sano, Y.; et al.
Year:
2005
Bibliographic source:
Journal of Occupational Health 47, 293-298

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: the Chemical Substances Control Law (1986)
Deviations:
not specified
GLP compliance:
not specified
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Bismuth
EC Number:
231-177-4
EC Name:
Bismuth
Cas Number:
7440-69-9
Molecular formula:
Bi
IUPAC Name:
bismuth
Details on test material:
- Name of test material (as cited in study report): Bismuth
- Mean particle diameter: 10 µm
- Storage condition of test material: at room temperature
- Purity: 99.9%

Test animals

Species:
rat
Strain:
Crj: CD(SD)
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Japan, Inc.
- Age at study initiation: 5 weeks at study initiation
- Weight at study initiation: 154-176 g (males) and 128-147 g (females)
- Fasting period before study: about 18 hours prior to dosing
- Diet: animals were fed with a pellet diet (MF, Oriental Yeast Co., Ltd.)
- Water: ad libitum; tap water inradiated by UV rays after passing through a 5-µm filter
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2
- Humidity (%): 55 +/- 15
- Air changes (per hr): about 12 changes per hour
- Photoperiod: 12 hours dark/light cycle

No further details are given.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
The dosing volume (10 mL/kg) for individual animals was calculated based upon the most recent body weight.
No further details are given.
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
No details are reported.
Duration of treatment / exposure:
Throughout the 28-day dosing period.
Frequency of treatment:
Once a day in the morning.
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
40 mg/kg
Basis:
other: nominal concentration
Remarks:
Doses / Concentrations:
200 mg/kg
Basis:
other: nominal concentration
Remarks:
Doses / Concentrations:
1000 mg/kg
Basis:
other: nominal concentration
No. of animals per sex per dose:
6 rats of each sex in the low and mid dose group and 12 rats of each sex in the control and high dose group.
Control animals:
yes
Details on study design:
Dose selection rationale:
- Prior to the 28-d oral toxicity study, a preliminary dose-finding study (dose Ievels: 0, 100, 500, and 1000 mg/kg; number of animals, 3 males and 3 females per group) was conducted.
- No changes attributable to the test substance on clinical signs, body weights, haematology, organ weights (brain, thymus, liver, kidney, adrenal glands, spleen, testis, and ovary) and during necropsy were observed.
- Thus, the highest dose level was set at 1000 mg/kg and the medium and lower dose levels were set at 200 and 40 mg/kg, respectively.
Positive control:
No positive control was tested.

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: clinical signs were observed twice a day (before and after administration) throughout the dosing period, and once a day in the morning during the recovery period.

BODY WEIGHT AND FOOD CONSUMPTION: Yes
- Time schedule for examinations: body weights of all animals and gross weights of feeders were measured once a week.

FOOD EFFICIENCY: No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on days of the scheduled necropsy.
- Anaesthetic used for blood collection: Yes; animals were anesthetised by intraperitoneal injection of sodium thiopental, and blood samples were collected via the posterior vena cava .
- Parameters examined: erythrocyte count (RBC), haemoglobin concentration (Hb), haematocrit value (Ht), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), reticulocyte count, platelet count (PLI), prothrombin time (PT), activated partial thromboplastin time (APTT), leukocyte counts (WBC), and differential leukocyte counts.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on days of the scheduled necropsy.
- Parameters examined: aspartate aminotransferase (ASAI), alanine aminotransferase (ALAT), y-glutamyltransferase (y-GT), alkaline phosphatase (ALP), total bilirubin, blood urea nitrogen (BUN), creatinine, glucose, total cholesterol, triglycerides, total protein, albumin, A/G ratio, calcium, inorganic phosphorus, sodium (Na), potassium (K), and chlorine (Cl).

URINALYSIS: Yes
- Time schedule for collection of urine: fresh urine samples from six males and six females in each group were collected on day 27. Because no changes attributed to bismuth were found during the dosing period, no examinations were conducted at the end of the recovery period.
- Parameters examined: pH, protein, glucose, ketone bodies, bilirubin, occult blood, urobilinogen.

NEUROBEHAVIOURAL EXAMINATION: No data
Sacrifice and pathology:
GROSS PATHOLOGY: Yes.
After blood sampling, all animals were sacrificed by exsanguination via the abdominal aorta and then subjected to necropsy. The following organs of all animals were weighed: brain, liver, kidney, adrenal glands, thymus, spleen, testis, and ovary. Relative organ weights were calculated from body weights on each necropsy day.

HISTOPATHOLOGY: Yes.
Histopathological examination was performed on the heart, liver, spleen, kidneys, and adrenals obtained from the animals of the control and 1000 mg/kg groups, and on gross lesions of low and mid dose group animals. Haematoxylin and eosin staining specimens were prepared according to the standard procedure and then microscopically examined. Because no changes attributed to bismuth were found, no histopathological examination of organs and tissues, except for gross lesions, was conducted in animals of the recovery groups.
Other examinations:
No further data are reported.
Statistics:
A multiple comparison test to analyse statistical significance in the numerical data (body weight, food consumption, haematology, blood chemistry, and organ weights) was used. If there was statistical significance in the data between groups, Dunnett's test or a Dunnett-type rank-sum test was conducted. Statistical significance in graded categorical data (urinalysis, necropsy findings and histopathological findings) was analysed by a x b chi-square test. If statistically significant data were found, data obtained from the control group were compared with those obtained from each dose group using Armitage's chi-square test. A significance level of 5% and 1% was set for all statistical analysis.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
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:
no effects observed
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
No abnormal clinical signs were observed in any animal during the dosing and recovery periods.

BODY WEIGHT AND WEIGHT GAIN
No significant body weight differences between the control group and any treatment group were observed in any animal during the dosing and recovery periods.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
No significant food consumption differences between the control group and any treatment group were observed in any animal during the dosing and recovery periods.

HAEMATOLOGY
No significant haematological change was found attributable to bismuth after the dosing period.
After the recovery period, a significantly higher value of the ratio of monocytes versus leukocytes (%) was observed in males of the 1000 mg/kg group, and a significantly lower value of leukocyte count was observed in females of the 1000 mg/kg group, as compared with the control group.

CLINICAL CHEMISTRY
A significantly higher value of potassium was observed in males of the 40 mg/kg group, and a significantly higher value of total protein in females of the 1000 mg/kg group was seen after the dosing period. After the recovery period, a significantly lower value of urea nitrogen was observed in males of the 1000 mg/kg group.
The higher value of potassium in males observed after the dosing period and the lower value of blood urea nitrogen in males after the recovery period were not related to bismuth administration, based upon their incidences (no dose-dependency). The higher value of total protein may not be related to the effect of bismuth, because there were neither changes in other parameters of protein nor changes in the liver involved in protein synthesis.

URINALYSIS
There were no significant differences between the control group and any treatment group in the urinalysis during the dosing period.

ORGAN WEIGHTS
Significantly lower values of absolute and relative thymus weights were found in female rats of the 200 mg/kg group after the dosing period, and significantly higher values of these weights were seen after the recovery period in males of the 1000 mg/kg group, whereas female rats of the 1000 mg/kg group showed a significantly higher value of absolute adrenal organ weight after the recovery period.
The significantly lower values of absolute and relative thymus weights in females after the dosing period, the significantly higher values of these weights after the recovery period in males, and the significantly higher values of absolute adrenal organ weights after the recovery period in females were not related to bismuth administration, since their incidences were not dose-dependent.

GROSS PATHOLOGY AND HISTOPATHOLOGY
Focal myocardial degeneration and fibrosis in the heart, microgranuloma and focal necrosis in the liver, basophilic urinary tubules, cysts, pelvic dilatation, hyaline droplets in the proximal urinary tubular epithelium, and focal interstitial infiltration of lymphocytes in the kidneys were observed, but these changes were not statistically significant.

No further details are given.

Effect levels

Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: clinical signs; mortality; body weight; food consumption; haematology; clinical chemistry; urinalysis; gross pathology; organ weights and histopathology

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
There were no significant changes attributed to treatment with bismuth on clinical signs, body weights, food consumption, haematology, clinical chemistry, urinalysis, organ weights, necropsy, or histopathological findings in the 28-day repeated oral dose toxicity study. As a result of the findings, the no-observed-adverse-effect level (NOAEL) of bismuth was determined to be 1000 mg/kg for males and females.