Caesium nitrate

Toxicity to reproduction

Administrative data

Endpoint:

screening for reproductive / developmental toxicity

Remarks:

based on test type (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-01-30 to 2013-03-27

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:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

(1995)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OTS 798.4420 (Preliminary Developmental Toxicity Screen)

Version / remarks:

(2000)

Deviations:

no

Principles of method if other than guideline:

No cross-reference

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Caesium nitrate

EC Number:

232-146-8

EC Name:

Caesium nitrate

Cas Number:

7789-18-6

Molecular formula:

Cs.HNO3

IUPAC Name:

caesium nitrate

Test material form:

other: solid

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Toxi-Coop Zrt. Cserkesz u. 90. H-1103 Budapest Hungary
- Age at study initiation: (P) 10 wks; (F1) x wks
- Weight at study initiation: (P) Males: x-x g; Females: x-x g; (F1) Males: x-x g; Females: x-x g

- Fasting period before study:

- Housing: Before mating: 2 animals of the same sex/ cage; mating: 1 male and 1 female / cage; pregnant females will be housed individually. Males after mating: 2 animals / cage
- Diet: 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, and tap water from municipal supply, as for human consumption, from 500 mL bottles ad libitum.
- Water: drinking water
- Acclimation period: 20 days

ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 3 °C
- Humidity: 30 - 70 %
- Air changes: 8-12 air exchanges/hour by central air-condition system.
- Photoperiod: 12 hours daily, from 6.00 a.m. to 6.00 p.m.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

physiological saline

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The test item will be formulated in the vehicle in concentrations of 40, 10 and 2 mg/mL. Formulations will be prepared in the formulation laboratory of Test Facility daily or according to stability results for some days before application.


VEHICLE
- Justification for use and choice of vehicle: Salsol (Physiologic saline); the test item is soluble in the vehicle which is untoxic for rats.
- Concentration in vehicle: 100 %
- Amount of vehicle: 5 mL/kg bw/day
- Lot/batch no.: 4280612

Details on mating procedure:

Mating was started 2 weeks after the initiation of treatment. One female and one male of the same dose group (1:1 mating) were placed in a single cage. Females remained with the same male during 14 days. Pairs were changed within a dose group thereafter; females were paired with not mated males then with proven males, if it was necessary,.
Each morning a vaginal smear was prepared and stained with 1 % aqueous methylene blue solution. The smear was examined with a light microscope. The presence of vaginal plug or sperm in the vaginal smear was considered as evidence of copulation (day 0 of pregnancy as defined by OECD 421). Sperm positive females were caged individually.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The suitability of the chosen vehicle for the test item at the intended concentrations was analytically verified up front. A sufficient recovery and stability in the chosen vehicle were verified over the range of relevant concentrations at the appropriate frequency of preparation. Recovery of cesium nitrate from Physiologic saline formulations was 94 % at ~1 and ~100 mg/mL concentrations. The test item proved to be stable in physiologic saline formulations at ~1 and ~100 mg/mL concentration levels at least for 3 days at room temperature. Concentration of the test item in the dosing formulations varied from 99 % to 100 % of nominal concentrations.

Duration of treatment / exposure:

The test item was administered in a single dose by oral gavage on a 7 days/week basis, every day at a similar time. Control animals were treated concurrently with the vehicle only. Animals were not treated on the day of gross pathology.
Dosing of both sexes began after 20 days acclimatization and was continued up to and including the day before the necropsy.
The mating phase started after 14-days of pre-mating. Rats of this strain have already reached full sexual maturity at the age of 12 weeks.
Males were dosed for 56 days (14 days pre-mating and 9 days mating plus 33 days post mating period), then they were sacrificed. Elongated treatment was reasoned by sperm analysis.
Female animals were dosed for 14 days pre-mating, during mating period, through gestation and up to lactation days 3 - 7 (altogether for 40 – 49 days, depending on date of mating).

Frequency of treatment:

Animals were treated once per day.

Details on study schedule:

Males were dosed for 56 days (14 days pre-mating and 9 days mating plus 33 days post mating period), then they were sacrificed. Elongated treatment was reasoned by sperm analysis. Female animals were dosed for 14 days pre-mating, during mating period, through gestation and up to lactation days 3 - 7 (altogether for 40 – 49 days, depending on date of mating). The day of delivery (viz. when parturition was complete) was defined as day 0 post-partum. Non-pregnant and not delivered female animals were treated up to and including the day before necropsy (altogether for 40 days).

Doses / concentrations

Remarks:

Doses / Concentrations:
10, 50, 200 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

12/ sex/ dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose setting with 200, 50 and 10 mg/kg bw/day are based on findings obtained in previous acute and repeated dose oral toxicity studies with chemically similar substances. The high dose was chosen with the aim of inducing toxic effects but no mortality or severe suffering of animals. The low dose was chosen to induce no toxic effect. In case of severe signs of toxicity high dose was planned to be reduced.

Positive control:

not applicable

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Animals were inspected for signs of morbidity and mortality twice daily (at the beginning and end of each working day).
- Cage side observations checked in table [No.?] were included.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: General clinical observations were made once a day, after treatment at approximately the same time, considering the peak period of anticipated effects after dosing. Pertinent behavioral changes, signs of difficult or prolonged parturition and all signs of toxicity including mortality were recorded including onset, degree and duration of signs.

BODY WEIGHT: Yes
- Time schedule for examinations: All parental animals were weighed with an accuracy of 1 g. Parental males were weighed on the first day of dosing (day 0), at least weekly thereafter and at termination. Parental females were weighed on the first day of dosing (day 0) then weekly, on gestation days 0, 7, 14 and 21 and on days 0 (within 24 hours after parturition) and 4 post-partum. Body weight of the female animals were additionally weighed on gestational days 10 and 17 in order to give accurate treatment volumes, but these data will not be evaluated statistically. Body weight data were reported individually for adult animals.

FOOD CONSUMPTION:
The food consumption will be determined with a precision of 1 g weekly by reweighing the non-consumed diet during the treatment period (pre-mating, gestation days 0, 7, 14 and 21, lactation days 0 and 4) except during mating phase.

Oestrous cyclicity (parental animals):

Mating was started 2 weeks after the initiation of treatment. One female and one male of the same dose group (1:1 mating) were placed in a single cage. Females remained with the same male during 14 days. Pairs were changed within a dose group thereafter; females were paired with not mated males then with proven males, if it was necessary,.

Sperm parameters (parental animals):

Parameters examined in male parental generations:
Sperm analysis were made from 5 control and 5 high dose males at the necropsy. One-side testes and epididymides was used for enumeration of spermatids and sperm reserves, respectively. For this, same subset of males, sperm from the ductus deferens was collected for evaluation of sperm motility and sperm morphology. As treatment related effects are seen in the high dose group, then the lower dose groups were be evaluated.

Quantitative examination
The total number of homogenization of testes sperm was enumerated. One side testes and epididymides were frozen at the necropsy and enumeration was performed later.

Qualitative examinations
Sperm motility was determined from ductus deferens of the same animals as enumeration at the necropsy. For the determination of the sperm motility the mean percentage of motile sperms was determined. Both numbers of motile and immotile sperms was recorded. Two samples were prepared from each animal. A morphological evaluation of ductus deferens sperms sample was performed from the same animals. Sperm was examined as fixed, wet preparations and classified as either normal or abnormal (isolated heads, misshapen heads and/or tails).

Litter observations:

Each litter was examined as soon as possible after delivery to establish the number and sex of pups, stillbirths, live births, runts (pups that are significantly smaller than normal pups), and the presence of gross abnormalities.
Live pups were counted, sexed and weighed within 24 hours of parturition (on the day when parturition was complete) and day 4 post-partum with an accuracy of 0.01 g.
In addition to the observations on parent animals, any abnormal behaviour of the offspring was observed.
All the litters were checked and recorded daily for the number of viable and dead pups. The dead pups found were subjected to necropsy by a macroscopic examination. On day 0 of lactation, a lung flotation test was performed on all pups found dead to separate stillborns from those that died after delivery. The lung flotation test is negative for stillborns (pups that died intrauterine) but positive for pups that died after delivery.

Postmortem examinations (parental animals):

Gross necropsy was performed on each animal one day after the last treatment. Animals were anesthetized by Isoflurane and then were exsanguinated.
After examination of the external appearance the cranial, thoracic and abdominal cavities were opened and the appearance of the tissues and organs were observed, and any abnormality was recorded with details of the location, color, shape and size. Special attention was paid to the organs of the reproductive system. The number of implantation sites and of corpora lutea was recorded.
The uterus with cervix, vagina, testes, epididymides, prostate, and seminal vesicles with coagulating glands, ovaries, pituitary of all adult animals were preserved. Testes and epididymides were preserved in modified Davidson solution, all other organs in 4 % buffered formaldehyde solution.

Postmortem examinations (offspring):

GROSS NECROPSY
Parameters listed below were evaluated.
Litter weight on postnatal days 0 and 4
Mean body weight gain per litter between postnatal days 0-4
Number of live births per litter, and number of viable pups per litter on postnatal days 0 and 4
Survival Index of pups on postnatal day 4
Sex ratio % (on postnatal days 0 and 4)

Statistics:

The statistical evaluation of appropriate data will be performed with the statistical program package SPSS PC+4.0. The homogeneity of variance between groups will be checked by Bartlett’s homogeneity of variance test. Where no significant heterogeneity is detected a one-way analysis of variance (ANOVA) is carried out. If the obtained result was significant, Duncan Multiple Range test was used to access the significance of inter-group differences. Getting significant result at Bartlett’s test the Kruskal-Wallis analysis of variance was used and the inter-group comparisons was performed using Mann-Whitney U-test. Chi2 test was performed if feasible.

Reproductive indices:

The following reproductive indices were calculated: Male mating index, female mating index, male fertility index, female fertility index, gestation index. The formulas for calculation can be found below in "Any other information on materials and methods incl. tables".

Offspring viability indices:

The offspring viability indices were calculated: survivla index. The formulas for calculation can be found below in "Any other information on materials and methods incl. tables".

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

effects observed, treatment-related

Reproductive performance:

effects observed, treatment-related

Details on results (P0)

Mortality
There was no mortality in 200, 50 or 10 mg/kg bw/day or control group during the course of study.

Clinical Observations
Daily Observations
There were no toxic signs related to the test item effect at the daily clinical observations. The behavior and physical condition of animals were considered to be normal at each dose level (200, 50 and 10 mg/kg bw/day) during the entire observation period.
Scar was noted for one male and one female animal of 200 mg/kg bw/day group on the nose and on the neck, respectively. Scar is a common dermal finding in this strain of experimental rats and was had no toxicological meaning in this study.

Detailed Weekly Observations
Test item related clinical signs were not detected at the weekly detailed observations in male or female animals at any dose level during the entire observation period (pre-mating, mating, post-mating, gestation or lactation periods).
Scar as described above was observed in one male and one female animal of 200 mg/kg bw/day group.

Body Weight
A test item influence on the body weight development was observed in male and female animals at 200 mg/kg bw/day.
More specifically, when compared to animals of the control group the body weight gain was statistically significantly reduced in male animals of 200 mg/kg bw/day group on weeks 3, 4, 5, if summarized (total body weight gain between Days 0 and 55) which resulted in a slight but statistically significantly reduced body weight during the entire post-mating period. Compared to the control group, statistical significances were detected for reduced mean body weight gain of the male animals of 200 mg/kg bw/day group during the mating period, between Days 27 and 34, and for the total body weight gain.
The mean body weight and body weight gain of dams of 200 mg/kg bw/day were slightly but statistically significantly reduced with respect to the control on gestation day 21, between gestation days 14 and 21, as well as if summarized during the entire gestation period (between gestation days 0 and 21).
The body weight development was not affected in the male or female animals treated with dose levels of 50 or 10 mg/kg bw/day with respect to the concurrent controls.

Food Consumption
Compared to the control animals, statistically significance was observed in 200 mg/kg bw/day group for the slightly reduced mean food consumption of male animals on week 2, during the entire post-mating period and of dams between lactation days 0 and 4.

Delivery Data of Dams
Compared to the control animals, a test item influence on the delivery data (mean number of post-implantation loss, total births, liveborns and viable pups) was detected at 200 mg/kg bw/day.
More specifically, for the 200 mg/kg bw/day treatment group the mean number of post-implantation loss exceeded the control value by a value of 1.7, while the mean number of total births per litter (8.36), liveborns per litter 7.56) and viable pups per litter (7.64) were statistically significantly reduced as compared to the control (10.55, 10.55 and 10.55, respectively). However, these findings only slightly differ with respect to the untreated control and to historical control data but a causal link to the treatment with the test item cannot be excluded.
Furthermore, the mean number of liveborns was slightly higher in dams of 50 mg/kg bw/day group with respect to the control group. This slight difference is due to biological variation has no biological or toxicological significance.

Reproductive Performance
There were no test item related differences between the control and test item treated male animals in the examined parameters of reproductive performance.
Statistical significances were noted for the higher percentage of fertile males and pregnant females, consequently for higher fertility indices (male and female) and for the less percentage of infertile males and non-pregnant females in all test item treated groups (200, 50 and 10 mg/kg bw/day). The gestation index was slightly less in dams of 200 mg/kg bw/day. These slight differences with respect to control were indicative of biological variation and had no toxicological relevance.

Necropsy
No test item related alterations were found at the macroscopic observations of organs and tissues at the necropsy in male and female animals at any dose level (200, 50 and 10 mg/kg bw/day).
Late embryonic death was observed in both uterine horns of the not delivered dam of 200 mg/kg bw/day and in two dams of the control group (one side, both). Scab on the nose and on the neck was detected in one male and one female animal, respectively, of 200 mg/kg bw/day group. The above mentioned are individual findings which have no toxicological relevance.

Organ Weight
The testes weight (absolute) and epididymides weights (absolute and relative referred to body and brain weights) were slightly but statistically significantly lower than in the control group at 200 mg/kg bw/day. However, the values remained within the ranges of the historical control values.

Sperm Examinations
Sperm examinations revealed a test item related damage in the motility and morphology of sperm cells at 200 mg/kg bw/day.
The mean percentage of immotile sperms and sperm cells with abnormal morphology (separated head and tail) was statistically significantly higher for the 200 mg/kg bw/day group (91.5 and 11.2 %, respectively) as compared to the control group (12.6 and 0.1 %, respectively). Accordingly, the percentage of motile sperm cells and sperms with normal morphology (head and tail connected) was statistically significantly lower in animals of 200 mg/kg bw/day group with respect to the control.
There was no significant difference in the total sperm cell count between the control and test item treated groups (200, 50 and 10 mg/kg bw/day).

Histopathology
Histological examination of the male and female genital organs (testes, epididymides and ovaries) did not reveal any toxic or other test item related alterations at 200 mg/kg/bw/day dose.
In one control (1/12) and in one 200 mg/kg bw/day dose treated (1/12) animal, decreased intensity of spermatogenesis and lack of mature spermatozoa in the seminiferous tubuli of testes and in the ductuli of epididymides. In the seminiferous tubuli of affected animals decreased number of spermatids was observed, however the Sertoli-cells and spermatogonia were intact, suggesting a reversible phenomenon. Some giant-cells were detected in the tubuli of epididymides. Regarding the incidence and severity of these findings (marked degree in one control and moderate degree in one treated animal) these findings were considered as individual disorder and were not related to the test item effect in the high dose group.
In the remaining male animals (11/12 at 200 mg/kg bw/day; 12/12 at 50 mg/kg bw/day; 12/12 at 10 mg/kg bw/day; 11/12 in the control group) the investigated organs of reproductive system (testes, epididymides) were histologically normal and characteristic on the sexually mature organism in all cases of control and treated groups.
The various spermatogenic cells (the spermatogonia, the spermatocytes, the spermatids and spermatozoa), representing different phases in the development and differentiation of the spermatozoons and the interstitial cells were the same in quantity and morphologically in the testes of investigated control and treated animals. Histologically, epididymides were normal in all cases as well. The ductuli of epididymides were crammed with nature spermatozoa.
In the female animals including non-pregnant and not delivered animals, the ovaries had a normal structure characteristic for the species, age and phase of sexual cycle. The cortex contained primary, secondary and tertiary follicles and corpora lutea, indicating the active maturation of oocytes and ovulation. The epithelial capsule and ovarian stroma were normal in all cases as well.

Effect levels (P0)

1

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: reduced body weight, reduced food consumption, slightly reduced weights of testes and epididymides

2

Dose descriptor:

NOAEL

Remarks:

Reproductive perfomance

Effect level:

50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: changes in delivery data of dams, slightly reduced weights of testes and epididymides, reducded sperm motility and changes in sperm morphology.

Results: F1 generation

General toxicity (F1)

Clinical signs:

effects observed, treatment-related

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

effects observed, treatment-related

Histopathological findings:

not examined

Details on results (F1)

Mortality
When compared to the untreated control, a variation on the extra uterine mortality of offspring was observed in 200 mg/kg bw/day group. In the 200 mg/kg bw/day group the litter mean and percentage of dead (missing, found dead and early euthanized) offspring were statistically significantly higher than in the control group between postnatal days 0 and 4. The mean number of the live-borns (male + female, female) and viable offspring on the postnatal days 0 (male + female, female) and 4 (male + female, male and female) were statistically significantly lower than in the control group in group of 200 mg/kg bw/day. However, these findings only slightly differ with respect to the untreated control but a causal link to the treatment with the test item cannot be excluded.
The number and percentage of liveborns and viable offspring, extra uterine mortality between postnatal days 0 and 4 were similar in the control, 50 and 10 mg/kg bw/day groups.

Sex Distribution
There were no significant differences between control and test item treated groups in the ratio or in the litter means of genders on postnatal days 0 or 4.

Clinical Observations
The number and percentage of offspring with clinical signs (not suckled, cold) and number and percentage of missing (cannibalized) offspring were significantly higher in the 200 mg/kg bw/day group comparing to their control.
A hole on the skullcap was observed in one male pup of 200 mg/kg bw/day group, which therefore was euthanized on postnatal day 0. This individual findings was considered as incidental.
Test item related clinical signs did not appear in the pups of 50 or 10 mg/kg bw/day groups. Abnormal mandible as individual variation was noted for one male pup in group of 10 mg/kg bw/day.

Body Weight
Variations on the body weight of offspring in 200 mg/kg bw/day group were detected.
More specifically, compared to the control group, the mean litter weight and the mean litter weight gain were statistically significantly less at 200 mg/kg bw/day group on postnatal days 0 and 4, as well as between postnatal days 0 and 4, respectively. Although different to the untreated control, these values remained within the ranges of the historical control data. Similarly, the mean offspring’s weight and weight gain remained below the control value in 200 mg/kg bw/day group on postnatal days 0 and 4, as well as between postnatal days 0 and 4. However, these findings only slightly differ with respect to the untreated control but a causal link to the treatment with the test item cannot be excluded. Statistical significances were also detected at the less mean body weight of pup in 50 mg/kg bw/day group at the birth and on postnatal day 4. However the differences were with low degree in the middle dose group with respect to the control therefore was not considered to be toxicologically relevant.
The mean litter weight and mean pup weight were similar in the control and 10 mg/kg bw/day dose treated groups, no test item related changes were found.

Necropsy
The external examinations revealed abnormal findings in individual pups of 200 mg/kg bw/day: one with edemic and deformed lips, one stillborn pup with morphological alterations on the head (cranium and splancnocranium) and one euthanized pup with a hole on the skullcap. As these isolated findings were observed only in individual pubs from different litters and were not associated with other morphological alterations, a test item relationship is considered as unlikely. Thus, these scattered occurrences are finally considered as incidental.
In one pup of 10 mg/kg bw group, the mandible was abnormal.
Test item related macroscopic alterations were not found in viscera of offspring subjected to gross pathological examination.

Effect levels (F1)

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: variations in offspring development were detected between postnatal days 0 and 4.

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The reprotoxic and developmental properties of cesium nitrate were assessed in a study performed according to OECD Guideline 421 in rats.
Based on the results, the No Observed Adverse Effect Levels (NOAEL) were determined as follows:
NOAEL for male rats: 50 mg/kg bw/day
NOAEL for female rats: 50 mg/kg bw/day
NOAEL for reproductive performance of the male rats: 50 mg/kg bw/day
NOAEL for reproductive performance of the female rats: 50 mg/kg bw/day
NOAEL for F1 Offspring: 50 mg/kg bw/day

Executive summary:

The purpose of this reproduction/developmental toxicity screening test, conducted according to OECD Guideline 421, was to provide initial information concerning the effect of the test item cesium nitrate on male and female reproductive performance such as gonadal function, mating behavior, conception, pregnancy, parturition as well as on development of the F1 offspring from conception to day 4 post-partum associated with oral administration to rats at repeated doses. Four groups of Hsd.Brl.Han:Wist rats (n=12/sex/group) were administered orally (by gavage) once a day at 0 (vehicle only), 200, 50 and 10 mg/kg bw/day at concentrations of 0, 40, 10 and 2 mg/mL corresponding to 5 mL/kg bw dose volume. The suitability of the chosen vehicle for the test item at the intended concentrations was analytically verified upfront. Cesium nitrate in physiologic saline was stable for 72 hours at room temperature. Concentration of the test item in the dosing formulations varied from 99 % to 100 % of nominal concentrations at both analytical occasions, thereby confirming proper dosing. All animals of the parent (P) generation received test item or vehicle prior to mating (14 days) and throughout mating. Test item or vehicle was administered to male animals post mating (altogether for 56 days) up to the day before the necropsy. For dams, test item was administered through the gestation period and up postpartal days 3 - 7 (altogether for 40 – 49 days), i.e. up to the day before the necropsy. Observations included mortality, clinical signs, body weight, food consumption, mating, pregnancy and delivery process, as well as development of pups. The dams were allowed to litter, and rear their young up to termination on days 4 postpartum. Pups were weighed and observed for possible abnormalities. Four pups were fixed in isopropanol and stained with Alizarin-Red for skeletal examinations due externally observed abnormalities. All parental animals were subjected to gross pathology one day after the last treatment. Histopathology examination was performed on the testes, epididymides in all male animals (control, low, mid and high dose groups) and on ovaries in female animals of the control and high dose groups.

 

Results

Mortality

There was no mortality in parental animals at any dose level (200, 50 10, and 0 mg/kg bw/day groups).

 

Clinical observation

Toxic signs related to the test item were not found at general daily and detailed weekly clinical observations. The behavior and physical condition of animals were normal during the entire observation period (pre-mating, mating, post-mating, gestation and lactation periods).

 

Body weight and body weight gain

A test item related depression of the body weight development was detected in male animals at 200 mg/kg bw/day from week 3 up to the end of the study. The body weight development of the parental female animals of 200 mg/kg bw/day was reduced during the last week of the gestation.

 

Food consumption

The daily mean food consumption was reduced in male animals at 200 mg/kg bw/day on week 2 and during the entire post mating period and in female animals of 200 mg/kg bw/day during the lactation period.

 

Reproduction

Variations on the delivery data of dams (higher mean number of post-implantation loss, less total births, less live-borns and viable pups with respect to their controls) were detected at 200 mg/kg bw/day. These findings only slightly differ with respect to the untreated control but a causal link to the treatment with the test item cannot be excluded. There were no differences between the control and test item treated groups (200, 50 and 10 mg/kg bw/day) in the reproductive performance of male and female animals.

 

Necropsy

Specific macroscopic alterations related to the test item were not found in the parental animals during the necropsy.

 

Organ weight

The testes weight (absolute) and epididymides weights (absolute and relative to body and brain weights) were slightly less at 200 mg/kg bw/day with respect to the untreated control. However, the values remained within the ranges of the historical control values.

 

Sperm examinations

Sperm examinations revealed a test item related damage with regards to motility and morphology of sperm cells at 200 mg/kg bw/day.

 

Histopathology

Histopathological examinations did not reveal any toxic or other test item related changes in the testes and epididymides of male animals at 200, 50 or 10 mg/kg bw/day dose level or in ovaries of female animals of 200 mg/kg bw/day group.

 

Offspring

Variations on the offspring development were observed in the slightly higher extra uterine mortality (number and percentage) between postnatal days 0 and 4, and in the less litter weight, litter weight gain and mean pup’s weight and weight gain on postnatal days 0 and 4 in 200 mg/kg bw/day group. These findings only slightly differ with respect to the untreated control but a causal link to the treatment with the test item cannot be excluded. Morphological alterations of the skull were detected in single pups of different litters in the 200 mg/kg bw/day group. As these isolated findings were observed only in individual pubs from different litters and were not associated with other morphological alterations, a test item relationship is considered as unlikely. Thus, these scattered occurrences are finally considered as incidental.

 

Conclusion

Under the conditions of the present study, cesium nitrate caused reduced body weight, body weight gain, and reduced food consumption (male and female), and changes in delivery data of dams (post-implantation loss, live-borns, viable pups), damage in sperm motility and morphology, slightly reduced weights of testes, epididymides, after oral(by gavage) administration at 200 mg/kg bw/day to Hsd.Brl.Han:Wistar rats during the Reproduction/ Developmental Toxicity Screening Test. At 50 and 10 mg/kg bw/day, there were no test item related toxic alterations in the parental male or female animals. At 200 mg/kg bw/day, variations in offspring development were detected between postnatal days 0 and 4: higher incidence of clinical signs, higher extra uterine mortality, depressed body weight development (for litter and pup’s weights). These findings only slightly differ with respect to the untreated control but a causal link to the treatment with the test item cannot be excluded. Also morphological alterations of the skull in individual pubs of different litters were observed. These scattered occurrences, only observed in individual pubs from different litters, are considered as incidental.

Based on these observations the No Observed Adverse Effect Levels (NOAEL) were determined as follows:

NOAEL for male rats: 50 mg/kg bw/day

NOAEL for female rats: 50 mg/kg bw/day

NOAEL for reproductive performance of the male rats: 50 mg/kg bw/day

NOAEL for reproductive performance of the female rats: 50 mg/kg bw/day

NOAEL for F1 Offspring: 50 mg/kg bw/day