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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1976
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study performed with the substance analogue Strontium chloride hexahydrate. The study was not performed according to OECD guidelines, or GLP Principles. It is however a well-documented study and fulfills the data requirements of OECD guideline 408 with regard to the most important parameters. The hypothesis for the analogue approach is attached in section 13.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1977

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Rats received SrCl2 hexahydrate in a diet at dose levels of 0, 75, 300, 1200, and 4800 ppm for 90 days. Growth, food intake, behaviour and mortality were measured, extensive haematology and clinical biochemistry were carried out, organ weight was determined and complete histopathological examination was performed. In addition, X-ray photographs of the bones were taken and the Sr content of blood, bone and muscles was determined in additional groups of rats.
GLP compliance:
no
Remarks:
Study performed before GLP guidelines were in place.
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Strontium chloride hexahydrate
- Molecular formula (if other than submission substance): SrCl2.6H2O
- Impurities (identity and concentrations): Barium < 0.02%
- Supplier: Mallinckrodt, St. Louis, Missouri, USA

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: National Institute of Public Health
- Housing: wire cages, two in a cage according to sex
- Weight at study initiation: 40-60g (males and females; 90-day experiment; )130-170g (males and females; range-finding experiment)
- Diet: semi-purified diet (Muracon SSP-tox, Trouw Ltd., Putten, The Netherlands), ad libitum
- Water: tap water, ad libitum

ENVIRONMENTAL CONDITIONS
- conventional conditions

Administration / exposure

Route of administration:
oral: feed
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
90 days
Frequency of treatment:
Continuous exposure through diet
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 75, 300, 1200 or 4800 ppm
Basis:
nominal in diet
No. of animals per sex per dose:
10
Control animals:
yes, plain diet
Details on study design:
- Dose selection rationale:
The dosing was determined based on a range-finding experiment with 0, 3, 30, 300 and 3000 ppm in the diet.
Positive control:
No

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption was measured in week 2, 5, 9 and 12.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes

HAEMATOLOGY:Yes
- Time schedule for collection of blood: after 90 days (all animals); after 6 and 12 weeks (5 males/ group)
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10 females and 10 males of each group
- Parameters examined: Hb, Ht, erythrocute count, leucocyte count, MCV, MCHC and MCH


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: after 4 and 12 weeks (5 males/ group)
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10 females and 10 males of each group
- Parameters examined: ALT, Alkaline phosphatase, glycogen and urea content in the serum
- Microsomal liver enzymes (AH and APDM; 5 males/ dose in weeks 4 and 12), glycogen content in the liver (5 males at 8 weeks and 6/sex in week 12)

URINALYSIS: Yes
- Time schedule for collection of urine: after 12 weeks
- Animals fasted: No data
- How many animals: 10 female and 10 male rats
- Parameters examined: protein, blood, bilirubin and ketones, and pH (using Bililabstix® (Ames Cy.))

OTHER:
Strontium content was determined in bone, muscle and blood by X-ray spectrometry with a limit of detection of 1 mg/kg. Magnesium and calcium concentrations in the serum were determined by atomic absorption spectrometry. This was done in 5 controls in the beginning of the experiment and in 5 males per group after 4, 8 and 12 weeks. In weeks 9 and 12 analysis of the bones were performed of 2/sex of the controls and 5/dex at 4800ppm.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- Weight of brain, pituitary gland, heart, thyroid, liver, kidneys, spleen, adrenals, ovaries or testes, uterus or prostate was determined
HISTOPATHOLOGY: Yes
- Organs above, and also lungs, thymus, pancreas, mesenterial lymph nodes, stomach, duodenum, ileum, jejunum, coecum, colon, rectum, urinary bladder, nervus ischiadicus, musculus quadriceps and femur
Statistics:
Student's t-test was used to compare seperate 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 examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
After more than 11 weeks one control animal died during bleeding procedure.

BODY WEIGHT AND WEIGHT GAIN
No effects observed.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
No effects observed.

FOOD EFFICIENCY
No effects observed.

HAEMATOLOGY
A lower leucocyte count was found in males at 300 ppm, in absence of a dose-response this is considered not to be substance related.

CLINICAL CHEMISTRY
No significant changes in alkaline phosphatase activity, ALT and urea in serum were observed. The levels of Ca, Mg, and P in the blood were not changed at any dose level, and the Ca/P ratio remained constant. No significant changes in microsomal liver enzyme activities were detected. The glycogen concentration in the liver after 12 weeks showed a dose-related decrease, only significant in females at the highest dose level.

URINALYSIS
No significant changes detected.

ORGAN WEIGHTS
A significant increase of the relative thyroid weights was found for the males at the two highest dose levels. Relative pituitary weights of the females at 300 ppm and 4800 ppm were statistically significantly decreased. The relative prostate weights were statistically significantly decreased at 75 and 1200 ppm. In the absence of a dose-relationship, the effects on organ weights were considered not toxicologically relevant.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological examination revealed slight changes in the liver and thyroid. The changes consisted of a loss of glycogen in the liver and a slightly increased activity of the thyroid of the males in the highest dose group.

OTHER FINDINGS
Neither after 9 nor after 12 weeks changes could be noticed in the X-ray photographs of the animals.
Detectable amounts of Sr in blood and muscle were only noticed at the highest dose level: approx. 3 µg/ g wet tissue after 4 and 8 weeks, approx. 2 µg/ g wet tissue after 12 weeks in blood; approx. 2 µg/ g wet tissue in muscle at all examined time points compared to below detection limit in controls. Sr concentration in bone was elevated at all dose levels (at 4, 8 and 12 weeks (30, 68, 160 and 660 times control at 75, 300, 1200 and 4800 ppm resp. after 12 weeks). Concentrations did not increase over time (results are included in table).

Effect levels

Dose descriptor:
NOAEL
Effect level:
> 1 200 ppm
Based on:
test mat.
Sex:
female
Basis for effect level:
other: Based on decreased glycogen content in the liver at 4800 ppm. Based on an average weight of 250g and a daily intake of 21.7 g food, the NOAEL of 1200 ppm correlates with 104 mg test material/kg bw/day.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Results range-finding experiment:

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. Sr in blood and muscle were only noted at the highest dose level (3000 ppm): appr. 2 and 1 µg/ g wet tissue for resp. blood and muscle in females and appr. 2 and 4 µg/ g wet tissue for resp. blood and muscle in males. In the bone, Sr concentrations were raised at 300 and 3000 ppm to resp. 266 and 1451 µg/ g wet tissue in females and 232 and 1711 µg/ g wet tissue in males (approximate values) versus 43 and 28 µg/ g wet tissue in resp control females and males.

Strontium-content in µg/ g bone tissue in 5 male rats per group after 0, 4, 8 and 12 weeks:

   start 4 weeks  8 weeks  12 weeks
 0  35 ± 2  20 ± 17 10 ± 4  9 ± 4
 75 ppm    276 ± 30  240 ± 19  273 ± 49
 300 ppm    619 ± 64  463 ± 76  523 ± 87
 1200 ppm   1473 ± 107  1237 ± 103  1430 ± 100
 4800 ppm    6088 ± 267  5259 ± 486 5941 ± 783

Applicant's summary and conclusion

Conclusions:
A feeding study was conducted for 90 days with strontium chloride hexahydrate, with doses of 0, 75, 300, 1200 and 4800 ppm with male and female rats. If the increased concentrations of strontium in the bone can be considered a non-adverse effect, a NOAEL of 1200 ppm SrCl2.6H2O can be derived from this study, based on decreased glycogen content in the liver at 4800 ppm.
Executive summary:

A feeding study was conducted for 90 days with strontium chloride hexahydrate, with doses of 0, 75, 300, 1200 and 4800 ppm with male and female rats (10/ sex/ dose). No substance related mortality occurred, no clinical signs were noted. No effects were seen on body weight gain, food consumption and haematological parameters. The glycogen concentration in the liver after 12 weeks showed a dose-related decrease, only significant in females at the highest dose level. Detectable amounts of Strontium in blood and muscle were only noticed at the highest dose level (both sexes). Strontium concentration in bone was elevated at all dose levels in both sexes, the concentrations did not increase over time. A NOAEL of 1200 ppm strontium chloride hexahydrate can be derived from this study

(if the increased concentrations of strontium in the bone can be considered a non-adverse effect), based on decreased glycogen concentration in the liver at 4800 ppm. Based on an average weight of 250 g and a daily intake of 21.7 g food, the NOAEL of 1200 ppm correlates with 104 mg test material/kg bw/day.