Barium nitrate

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: Test procedure in accordance with generally accepted scientific standard and described in sufficient detail.

Data source

Reference

Reference Type:

publication

Title:

Subchronic toxicity of barium chloride dihydrate administered to rats and mice in the drinking water

Author:

Dietz DD, Elwell MR, Davis WE Jr, Meirhenry EF

Year:

1992

Bibliographic source:

Fundamental and applied toxicology 19, 527-537

Materials and methods

Principles of method if other than guideline:

Barium chloride dihydrate (BaCl2 * 2H2O) was given for 92 days to Fischer 344/N rats in their drinking water at levels of 0, 125, 500, 1000, 2000 and 4000 ppm.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

BaCl2.2H2O

IUPAC Name:

BaCl2.2H2O

Details on test material:

- Name of test material (as cited in study report): BaCl2.2H2O
- Analytical purity: 99.5% (EDTA titration)
- Lot/batch No.: 123120
- Other: source: Baker Chemical Co.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Simonsen Laboratories (Gilroy, CA)
- Age at study initiation: 32 days old
- Housing: five per cage in drawer-type polycarbonate cages. The shelves supporting the cages were covered with filter sheets.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: The animals were quarantined for 10 to 11 days after arrival, and representatives were necropsied to verify that they were grossly free of disease.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 - 24°C
- Air changes (per hr): 13.5 room vol/hour
- Photoperiod (hrs dark / hrs light): 12 hours on (from 06h30 to 18h30) and 12 hours off

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Solutions were made weekly in 19-liter quantities by dissolving weighed portions of the chemical in glass-distilled water.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The test substance was analyzed by EDTA titration. Dosage analyses performed on all levels before and after use, and at the beginning and midway through the test period, indicated that the concentrations were within 1 to 6% of the theoretical concentration.

Duration of treatment / exposure:

92 days

Frequency of treatment:

Exposures were continuous.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm

Remarks:

BaCl2.H2O, nominal in water

Doses / concentrations 2

Dose / conc.:

125 ppm

Remarks:

BaCl2.H2O, nominal in water

Doses / concentrations 3

Dose / conc.:

500 ppm

Remarks:

BaCl2.H2O, nominal in water

Doses / concentrations 4

Dose / conc.:

1 000 ppm

Remarks:

BaCl2.H2O, nominal in water

Doses / concentrations 5

Dose / conc.:

2 000 ppm

Remarks:

BaCl2.H2O, nominal in water

Doses / concentrations 6

Dose / conc.:

4 000 ppm

Remarks:

BaCl2.H2O, nominal in water

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

Animals were randomly assigned to groups of 10 per dose level after weight-sorting them by sex.

Examinations

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- All animals were observed twice daily for clinical signs of toxicity.

BODY WEIGHT: Yes
- Body weights were determined weekly

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Water consumptions were measured twice weekly.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: Yes
- Serum electrolyte determination: Blood for serum electrolyte determinations was taken by heart puncture from sodium pentobarbital-anesthetized rats before they were terminated for necropsy. Serium sodium and potassium were measured by flame ion emission using a Coleman Ca-51 fmale photometer. Calcium and phosphorus were measured using a Germeni miniature centrifugal analyzer in conjunction with a Gemeni loader.

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: Yes
- The behavioral test battery consisted of (1) undifferentiated motor activity, (2) forelimb and hindlimb grip strengths, (3) thermal sensitivity to a 55°C water bath, (4) startle response to acoustic and air-puff stimuli, and (5) hindlimb foot splay. These tests were performed on each animal at 0, 45 to 48, and 91 days of exposure and were performed sequentially in the above mentioned order. For the activity measurements, the movements of each animal were monitored electronically for 30 min. Grip strength and foot splay results were averaged after three trials while thermal sensitivity and startle response tests were conducted one time. The startle response test was repeated up to two times if no response was attained on the first trial.

OTHER:
Reproductive and fertility assessment are discussed in IUCLID section 7.8.1 Toxicity to reproduction.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
All animals were examined for gross lesions.
HISTOPATHOLOGY: Yes
The tissues of the animals were fixed in neutral-buffered 10% formalin. The brain, liver, right kidney, lung, thymus, right testis, heart, and adrenals were weighed before fixation. Complete histologic exams were performed on 30 or more tissues from animals of the 4000 ppm and the control groups. Tissues were trimmed, embedded in paraffin, sectioned to 6 µm thickness and stained with hematoxylin and eosin for microscopic examination.
Because histopathologic changes were observed in several tissues (thymus, spleen, kidneys, and lymph nodes) from rats in the 4000 ppm group, these tissues were examined from lower dose animals to determine a no-effect level.

Statistics:

Each parameter for which individual values were available was subjected to a linear least squares regression over the dose levels and the direction of the slope and the p value indicating the significance of the deviation of the slope from 0 was determined. Group means and standard deviations or standard errors were calculated from continuous variables. The multiple comparison procedure of Dunnett was employed for pairwise comparisons of these variables between dosed groups and controls. Fisher's exact test was used to make pairwise comparisons of discrete variables between dosed groups and controls and the Cochran-Armitage test was used to assess the significance of dose-related trends. Temporal and dose-related variations were evaluated using a repeated measures analysis of variance. When a collection of measurements was made on each animal, a multivariate analysis of variance was used to test for simultaneous equality of measurements across dose levels.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

effects observed, treatment-related

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

effects observed, treatment-related

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
Three of 10 male and 1 of 10 female rats in the 4000 ppm groups died during the last week of the study.

BODY WEIGHT AND WEIGHT GAIN
Body weights of both sexes in the 4000 ppm groups were significantly (p < 0.05) lower than controls.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
Water consumption was decreased in rats at some dose levels. Rats consumed approximately 70%.

NEUROBEHAVIOUR
Compared to their controls, rats exposed to 2000 ppm BaCl2 or lower did not show any consistent changes in behavioral indices (motor activity, fore-and hindlimb grip strength, and thermal sensitivity). Marginal although significant behavioral effects were noted at the 4000 ppm level in rats. These changes were probably a result of the overall BaCl2 toxicity observed at the 4000 ppm dose level. The behavioral effects observed at 4000 ppm level are as follows: decreased undifferentiated motor activity in female rats on day 91. No significant or dose-related effects were seen in the startle response to acoustic and air-puff stimuli or the hindlimb foot splay.

ORGAN WEIGHTS
Treatment-related depressed liver weights were observed among rats drinking 4000 ppm barium chloride. Absolute kidney weights were elevated in the 1000 and 4000 ppm female rats. Relative kidney weights were elevated among treated rats (males, 4000 ppm; females, 1000 ppm or greater) and mice (4000 ppm). Thymus weights were depressed among high-dose (4000 ppm) female rats who became moribund or died early in the study.

HISTOPATHOLOGY: NON-NEOPLASTIC
Treatment-related lesions associated with the barium chloride toxicity were present in the kidneys. The kidney changes were limited to a few foci of dilated tubules in the outer medulla or medullary rays. Tubular cell regeneration, casts, and crystals were not a feature of the renal lesions in rats. Lymphoid depletion was also present in the spleen and thymus of the early death rats.
There were no treatment-related histopathologic effects in the brain or other tissues of rats. In one female rat administered 4000 ppm BaCl2, there was moderate degeneration of the myocardium. This lesion was not clearly related to treatment; the morphologic features were similar to those seen in the spontaneously occurring cardiomyopathy (minimal to mild severity) which was present in most treated and control male and female rats in this study.

Effect levels

1

Dose descriptor:

NOEL

Effect level:

2 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: depressed body weight gains and chemically related lesions in the kidney and lymphoid tissue

2

Dose descriptor:

NOEL

Effect level:

61.1 mg/kg bw/day (nominal)

Based on:

other: Calculated as Ba2+

Sex:

male

Basis for effect level:

other: Individual effects observed at 2000 ppm barium chloride in drinking water (corresponding to the final barium dose of 61.1 mg Ba/kg bw/day to male rats) were regarded as not treatment-related and this dose levels represents the NOEL.

3

Dose descriptor:

NOEL

Effect level:

80.9 mg/kg bw/day (nominal)

Based on:

other: calculated as Ba2+

Sex:

female

Basis for effect level:

other: Individual effects observed at 2000 ppm barium chloride in drinking water (corresponding to the final barium dose of 80.9 mg Ba/kg bw/day to female rats respectively) were regarded as not treatment-related and this dose levels represents the NOEL.

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The no effect level for barium toxicity in this study based on depressed body weight gains and chemically related lesions in the kidney and lymphoid tissue was 2000 ppm BaCl2.2H2O (corresponding to the final barium dose of 61.1 and 80.9 mg Ba/kg bw/day (116.27 and 153.95 mg Ba nitrate/kg/day ) to male and female rats respectively) in the drinking water.