Caesium chloride

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: genome mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007-12-04 to 2008-01-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP and guideline compliant study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

1997

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

EEC Directive 2000/32, L 136/50

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5395 (In Vivo Mammalian Cytogenetics Tests: Erythrocyte Micronucleus Assay)

Version / remarks:

1998

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Caesium chloride

EC Number:

231-600-2

EC Name:

Caesium chloride

Cas Number:

7647-17-8

Molecular formula:

ClCs

IUPAC Name:

caesium chloride

Test material form:

solid: crystalline

Test animals

Species:

mouse

Strain:

other: CRL:NMRI BR mice

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: CHARLES RIVER (EUROPE) LABORATORIES INC. Toxi Coop Ltd. 1103 Budapest, Cserkesz u. 90.
- Age at study initiation: Young adult mice (8-9 weeks)
- Weight at study initiation: Preliminary test: Male: 27.5-30.8, Female: 23.2-25.7 g; main test (MNT): Male: 25.3-29.1 g; Female: 23.2-25.7 g
- Assigned to test groups randomly: yes: All animals were sorted according to body weight by computer and divided to weight ranges. There were equal number of animals from each weight group in each of the experimental groups assigned by randomisation.
- Housing: 5 animals/cage, expect of highest dose, where 7 animals/cage); cage type: II type polypropylene/polycarbonate
- Diet (e.g. ad libitum): Ssniff® SM R/M-Z+H "Autoclavable complete feed for rats and mice – breeding and maintenance" produced by ssniff Spezialdiäten GmbH, D-59494 Soest, Germany, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3 °C
- Humidity (%): 30-70 %
- Air changes (per hr): 12 air exchanges/hour
- Photoperiod (hrs dark / hrs light): 12 h light daily

IN-LIFE DATES: From: 04.12.2007 To: 03.01.2008

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

distilled water

Details on exposure:

A preliminary toxicity test was performed to identify the appropriate maximum dose level for the main test. The preliminary test also was used to determine whether there are large differences in toxicity between the sexes or not. Groups of three male and female mice were treated on two occasion, 24 hrs. apart by intraperitoneal injections at dose levels of 250, 500, 1000, 1250 and 1500 mg/kg bw. Animals were examined regularly for toxic signs and mortalities. The treatment volume was 10 mL/kg bw.

Duration of treatment / exposure:

The test/vehicle control items were administred by intraperitoneal injection on two occasions, 24 hrs. apart.

Frequency of treatment:

The test/vehicle control items were administred by intraperitoneal injection on two occasions, 24 hrs. apart.

Post exposure period:

Sampling was made once at 24 hours after final treatment.

Doses / concentrations

Remarks:

Doses / Concentrations:
250, 500, 1000 mg/kg bw /day on two occasions, 24 hrs apart, with a constant treatment volume of 10 mL/kg body weight
Basis:
other: intraperitoneal injection

No. of animals per sex per dose:

Five male and five female animals per dose group

Control animals:

yes, concurrent vehicle

Positive control(s):

Cyclophosphamide (positive control) was administered intraperitonealy on one occasion at a treatment volume of 10 mL/kg bw/day. Sampling was perfonned 24 hours after the treatment and five male and five female animals were used for sampling.

Examinations

Tissues and cell types examined:

Bane marrow smears

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION:
A preliminary toxicity test was performed to identify the appropriate maximum dose Ievel for the main test. Groups of three male and female mice
were treated on two occasions, 24 hrs apart with solutions of cesium chloride by intraperitoneal injection at dose Ievels of 250, 500, 1000, 1250 and 1500 mg/kg bw/day.

DETAILS OF SLIDE PREPARATION:
The bone marrow was flushed with foetal bovine serum (5 mL). After vortex mixing, the cell suspension was concentrated by centrifugation and the supernatant was discarded. Smears of the cell pellet was made on standard microscope slides. Slides were then dried at room temperature. Subsequently the slides were stained as follow: 1. Fixed for a minimum of 5 miutes in methanol and allowed to air-dry. 2. Stained with Giemsa solution (99 mg/mL distilled water) for 25 minutes. 3. Rinsing in distilled water. 4. Drying at room temperature (at least 12 hours). 5. Coating with E-Z-Mount xylene (SHANDON).

METHOD OF ANALYSIS:
Prior to microscopic analysis, one slide from each animal was given a code number for blind microscopic analysis. The code Iabels were covered the
original animal numbers to ensure that the slides were scored without bias. Two thousand polychromatic erythrocytes (PCEs) was scored per animal to assess the micronucleated cells. The frequency of micronucleated cells were expressed as percent of micronucleated cells based on the first 2000 PCEs counted in the optic field. The proportion of immature among total (immature + mature) erythrocytes was determined for each animal by counting a total of at least 200 immature erythrocytes.

Evaluation criteria:

The Micronucleus Test is considered acceptable if it meets the following criteria:
- The proportion of polychromatic erythrocytes among total erythrocytes in treated groups is not less than 20% ofthe control value.
- The frequencies of micronucleated polychromatic erythrocytes found in the negative and /or solvent controls falls within the range of historical Iabaratory control data.
- The positive control item should produce biologically relevant increases in the number ofmicronucleated polychromatic erythrocytes.
- Each treated and control group should include at least 5 analysable animals per sex.

Statistics:

The frequencies of micronucleated polychromatic erythrocytes in animals in the test and positive control groups were compared to the values found in the corresponding negative control group. Statistically analysis was performed using Kruskall Wallis Non Parametrie ANOV A test. Data were analysed separately formale and female animals.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range: 250, 500, 1000, 1250 and 1500 mg/kg bw/day
- Clinical signs of toxicity in test animals: No adverse reactions to treatment were observed in the mice dosed 250 mg/kg body weight/day. The male and female animals dosed at 500 mg/kg body weight/day showed a slight decrease in activity, straub tail, salivation, diarrhoea, piloerection and dyspnoea. The symptoms were observed between 5 min. and 1 hour after the treatment. No symptoms were observed thereafter. In the 1000 mg/kg body weight dose group, moderate decreased activity, straub tail, salivation, diarrhoea, piloerection and dyspnoea were observed after the treatment. The symptoms were observed between 5 min. and 2 hours after the treatment. The mice dosed at the 1250 mg/kg body weight/day dose Ievel showed moderate decreased activity , salivation, diarrhoea, piloerection, straub tail and strong dyspnoea. The symptoms were observed between 5 min. and 2 hours after the treatment. In the group dosed at 1500 mg/kg body weight/day, moderate decreased activity, salivation, diarrhoea, piloerection, straub tail and strong dyspnoea. The death (one male and one female) was observed within halfhour after the first treatment. On the second day the death was observed (two males and two females) within a similar timeframe.
- Evidence of cytotoxicity in tissue analyzed: Necropsy in group 1500 mg/kg bw/day: In animals which died early ( 4 of 6), pale raised areas were found in the lungs.


RESULTS OF DEFINITIVE STUDY
-Slight, statistically significant (p<0.05) differences were observed in the number of MPCE in the male mice at 24 hours after the last treatment with 500 and 1000 mg/kg bw/day of cesiumchloride. However, the values observed in these groups were well below the mean historical control value of this laboratory, consequently they were considered to be of no biologically significance. The intraperitoneal administration on two occasions, 24 hrs apart of 250 mg/kg bw/day, 500 mglkg bw/day and 1000 mg/kg body weight/day of cesium chloride did not induce any biologically relevant increase in the frequency of MPCEs in male or female mice at 24 after the last treatment compared to the vehicle control.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Under the conditions of this assay the test item cesium chloride did not induce any biologically relevant increase in the number of micronucleated polychromatic erythrocytes at dose Ievels of 250, 500 and 1000 mg/kg body weight after intraperitoneal administration on two occasions, 24 hrs apart in NMRI BR mice.
Cesium chloride did not show any genotoxic activity in this Mouse Micronucleus Test.

Executive summary:

Potential mutagenic activity of cesium chloride was examined in bone marrow of male and female NMRI BR mice. The frequencies of MPCEs for the untreated control mice were within an acceptable range and compatible with the historical control data for this laboratory. Cyclophosphamide treated mice (60 mg/kg bw) showed a large, statistically significant increase in the MPCEs number compared to the vehicle control, demonstrating an acceptable sensitivity of the test.

Slight, statistically significant (p<0.05) differences were observed in the number of MPCE in the male mice at 24 hours after the last treatment with 500 and 1000 mg/kg bw/day of cesiumchloride. However, the values observed in these groups were well below the mean historical control value of this laboratory, consequently they were considered to be of no biologically significance.

The intraperitoneal administration on two occasions, 24 hrs apart of 250 mg/kg bw/day, 500 mglkg bw/day and 1000 mg/kg body weight/day of cesium chloride did not induce any biologically relevant increase in the frequency of MPCEs in male or female mice at 24 after the last treatment compared to the vehicle control.

The percentage of PCE among total (polychromatic and normachromatic) erythrocytes in 1000 mg/kg bw/day dose groups of male was slightly lower than concurrent negative control value, but there was no clear evidence for test item induced hone marrow toxicity.

Under the conditions of this assay the test item cesium chloride did not induce any biologically relevant increase in the number of micronucleated polychromatic erythrocytes at dose Ievels of 250, 500 and 1000 mg/kg body weight after intraperitoneal administration on two occasions, 24 hrs apart in NMRI BR mice.

Cesium chloride did not show any genotoxic activity in this Mouse Micronucleus Test.