Strontium oxide

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Test procedure meets generally accepted scientific principles, acceptable for assessment The study had the following deficiencies: - purity, stability and physical form of the test item was not stated - males were used for the determination of strontium levels in blood, bone and muscle, but females were not investigated. - females were excluded from clinical chemistry examination, whereas males were investigated - food consumption was not measured weekly, but in week 2, 5, 9 and 12. - ophthalmological examination was missing - clotting potential was not investigated - incomplete gross pathology (X-ray photography only) - housing conditions were not described - acclimatisation period was not stated - baseline data for haematology and clinical chemistry were not provided - analytical verification of doses was missing - results were not present for all parameters (no tables)

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Short-term toxicity of strontium chloride in rats

Author:

Kroes, R. et al.

Year:

1977

Bibliographic source:

Toxicology 7: 11 - 21.

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

clinical chemistry only in males, ophthalmological examination missing, haematology incomplete, analytics missing

Principles of method if other than guideline:

A sub-chronic study was conducted with strontium chloride hexahydrate using groups of 10 male and 10 female Wistar rats. The rats were given the test substance at dose levels of 0, 75, 300, 1200 or 4800 ppm (0, 7.5, 30, 120, or 480 mg/kg/day, respectively) ad libitum via diet for a duration of 90 days. The following parameters were investigated: clinical signs/mortality, body weight, food consumption/food efficiency, haematology, clinical chemistry, urinalysis, organ weights, and histopathology. Additional males were used for the determination of the strontium levels in blood, bone and muscle, which were examined at different times during the study.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

strontium chloride hexahydrate

IUPAC Name:

strontium chloride hexahydrate

Constituent 2

Reference substance name:

Strontium chloride

EC Number:

233-971-6

EC Name:

Strontium chloride

Cas Number:

10476-85-4

Molecular formula:

Cl2Sr

IUPAC Name:

strontium dichloride

Constituent 3

Reference substance name:

10025-70-4

Cas Number:

10025-70-4

IUPAC Name:

10025-70-4

Test material form:

not specified

Details on test material:

- Name of test material (as cited in study report): strontium chloride hexahydrate (from Mallinckrodt, St. Louis, Missouri, U.S.A.)
- Molecular formula: SrCl2 6H2O
- Composition of test material, percentage of components: barium content less than 0.02 %

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS - SPF Wistar rats
- Source: National Institute of Public Health
- Weight: 40 - 60 g
- Housing: housed under conventional conditions, littermate-divided in wire cages, two in a cage according to sex
- Diet (ad libitum): semi-purified diet (Muracon SSP-tox, Trouw Ltd., Putten, The Netherlands); diet contained 0.05 % Mg, 0.75 % P, 0.85 % Ca and 1.8 I.U. Vit. D.3 per gram
- Water (ad libitum): tap water

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

no data

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

no data

Duration of treatment / exposure:

90 days

Frequency of treatment:

ad libitum

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 75, 300, 1200 or 4800 ppm strontium chloride hexahydrate
Basis:
nominal in diet

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 7.5, 30, 120 or 480 mg/kg bw/day strontium chloride hexahydrate (calculated from ppm values)
Basis:
nominal in diet

No. of animals per sex per dose:

Treatment group: 10 males / 10 females
(plus 10 males were used for the determination of the strontium levels in blood, bone and muscle in weeks 0, 4, 8 and 12)

Control group: 10 males / 10 females
(plus 15 males were used for the determination of the strontium levels in blood, bone and muscle in weeks 0, 4, 8 and 12)

Control animals:

yes, plain diet

Details on study design:

- Range-finding experiment:
Rats with an initial body weight of 130-170 g were divided into 5 groups each consisting of 3 females and 3 males, receiving 0, 3, 30, 300 and 3000 ppm strontium chloride hexahydrate in the diets respectively during two weeks.
The animals were weighed at the beginning of the experiment and after 1 and 2 weeks. Food intake was recorded during the experimental period and was measured per cage (two rats) and expressed as the average intake per day per rat. Food conversion was calculated, blood samples were taken at the end of the experiment and hematological investigation was restricted to haemoglobin, hematocrit and the number of erythrocytes and leucocytes. The mean cell volume, mean cell haemoglobin concentration, and mean cell haemoglobin were calculated.
At the end of the 2 weeks X-ray photographs were made of all animals. Strontium concentration was measured in blood, bone and muscle. Liver and kidneys were weighed and examined histopathologically by preparing paraffin sections (5 µm) stained with haemalum and eosin.

Results:
Behaviour, growth, food intake and food efficiency were not affected in the range-finding experiment. Haematological investigation revealed only a slight elevation of the total number of erythrocytes in males and females and a slight increase of the white cell count in the males at the highest dose level. No differences were found in liver and kidney weights and histopathological examination revealed no abnormalities. Strontium in blood and muscle were only noted at the highest dose level whereas from 300 ppm onwards increased concentrations were found in bone.

Positive control:

no data

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations checked: behaviour and mortality

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- food intake was measured in week 2, 5, 9 and 12.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

FOOD EFFICIENCY: Yes

WATER CONSUMPTION AND COMPOUND INTAKE: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: after 90 days of treatment
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10 males / 10 females
- Parameters examined: haemoglobin, haematocrit, number of erythrocytes, number of leucocytes, mean cell volume, mean cell haemoglobin concentration, and mean cell haemoglobin; blood picture was studied

CLINICAL CHEMISTRY: Yes
1) strontium, calcium, magnesium, phosphorous
- time schedule for collection of blood: in the beginning of the experiment (control group only) and after 4, 8 and 12 weeks (treatment groups only).
- animals fasted: No data
- how many animals: 5 control males and 5 males per treatment group

2) alanine aminotransferase, alkaline phosphatase, and urea content
- time schedule for collection of blood: after 6 and 12 weeks
- animals fasted: No data group
- how many animals: 5 males per group

3) microsomal liver enzymes (aniline hydroxylase and aminopyrine demethylase)
- time schedule for collection of blood: after 4 and 12 weeks
- animals fasted: No data group
- how many animals: 5 males per group

URINALYSIS: Yes
- Time schedule for collection of urine: after 12 weeks of treatment
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters examined: protein, blood, bilirubin, ketones and pH

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

In the ninth and the twelfth week of the experiment X-ray photographs were prepared from 2 females and 2 males of the control group and from 5 females and 5 males of the 4800 ppm dose group.

After 12 weeks the remaining animals were killed and the weight of brain, pituitary, heart, thyroid, liver, kidneys, spleen, adrenals, ovaries or testes, uterus or prostate was determined.
Histopathology of these organs and also of lungs, thymus, pancreas, mesenterial lymph nodes, stomach, duodenum, ileum, jejunum, coecum, colon, rectum, urinary bladder, nervus ischiadicus, musculus quadriceps and femur was carried out by preparing paraffin sections (5 µm) stained by haemalum and eosin.

The glycogen content in the liver was determined in 5 males after 8 weeks and in 6 females and 6 males after 12 weeks.

Determination of strontium in bone and muscle was conducted by X-ray spectrometry.

Statistics:

Student's t-test was used in order to observe differences between separate treatment groups and corresponding controls.

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:

no effects observed

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:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not specified

Details on results:

CLINICAL SIGNS AND MORTALITY
- behaviour was not affected.
- after more than 11 weeks one control female died during bleeding procedure.

BODY WEIGHT AND WEIGHT GAIN
- growth was not affected.

FOOD CONSUMPTION AND COMPOUND INTAKE
- food intake was not affected.

FOOD EFFICIENCY
- food efficiency was not affected

HAEMATOLOGY
- slightly elevated erythrocyte count noticed in the range-finding experiment was not confirmed in the 90-day study.
- 300 ppm dose group: lower leucocyte count was noticed in the males (not considered to be caused by the treatment, since at higher dose levels such an effect was not observed).

CLINICAL CHEMISTRY
- analysis of alkaline phosphatase, alanine aminotransferase and urea in serum did not reveal any significant changes although in the 4800 ppm dose group an indication of an increased activity of alkaline phosphatase was noticed.
- aniline hydroxylase and aminopyrine demethylase activities did not show any changes.
- levels of calcium, magnesium and phosphorous in the blood were not changed at any dose level, and the calcium/phosphorous ratio remained constant.
- calcium, magnesium and phosphorous concentrations in blood in all dose groups were higher after 8 weeks than after 12 weeks, which seems a physiological condition.
- detectable amounts of strontium were only noticed at the 4800 ppm dose level

URINALYSIS
- urinalysis did not show any abnormalities.

ORGAN WEIGHTS
- significant increase of the relative thyroid weights was found for the males at the 1200 ppm (control group: 0.0054 %; treatment group: 0.0072 %; P < 0.01) and 4800 ppm dose levels (control group: 0.0054 %; treatment group: 0.0068 %; P < 0.001).
- relative pituitary weights of the females at 300 ppm dose level (control group: 0.0074 %; treatment group: 0.0062 %; P < 0.05) and at 4800 ppm dose level (control group: 0.0074 %; treatment group: 0.0056 %; P < 0.01)were significantly decreased.
- relative prostate weights were significantly decreased at 75 ppm (control group: 0.128 %; treatment group: 0.092 %; P < 0.01) and 1200 ppm dose levels (control group: 0.128 %; treatment group: 0.101 %; P < 0.05).

GROSS PATHOLOGY
- neither after 9 nor after 12 weeks changes could be noticed in the X-ray photographs of the animals.

HISTOPATHOLOGY: NON-NEOPLASTIC
- slight changes in the liver and thyroid after blind examination.
- changes consisted of a loss of glycogen in the liver at the 4800 ppm dose group and a slightly increased activity in the thyroid of the males of the 4800 ppm dose group
- detectable amounts of strontium in muscle were only noticed at the 4800 ppm dose level
- detectable amounts of strontium in bone were elevated at all dose levels.
- glycogen concentration in the liver after 12 weeks showed a dose-related decrease, which was only significant in the females in the 4800 ppm dose group (control group: 22.4 ± 6.1 in mg/g liver; treatment group: 7.8 ± 3.7 in mg/g liver; P < 0.001).

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

300 ppm

Based on:

test mat.

Sex:

male

Basis for effect level:

other: NOAEL for strontium chloride hexahydrate is based on the significant increase of the relative thyroid weights, which was found for the males at the 1200 ppm and 4800 ppm dose levels.

2

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: NOAEL for strontium chloride hexahydrate calculated from ppm value.

3

Dose descriptor:

NOAEL

Effect level:

9.9 mg/kg bw/day (nominal)

Based on:

element

Remarks:

strontium

Sex:

male

Basis for effect level:

other: NOAEL calculated for strontium from data obtained for strontium chloride hexahydrate.

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

NOAEL (males): 300 ppm strontium chloride hexahydrate (equivalent to 30 mg/kg/day (nominal))
NOAEL (males): 9.9 mg strontium/kg/day (nominal)
The NOAEL is based on the significant increase of the relative thyroid weights, which was found for the males at the 1200 ppm and 4800 ppm dose levels (120 or 480 mg/kg/day strontium chloride hexahydrate, respectively).