Registration Dossier

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:
10 February 2003 to 30 May 2003
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2003
Report Date:
2003

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: OECD Guideline 421 (Reproduction/Developmental Toxicity Screening Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Purity: 98.57% dibutyltin dichloride

Test animals

Species:
rat
Strain:
Wistar
Details on species / strain selection:
-
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Deutschland, Sulzfeld, Germany.
- Age at study initiation: about 10-11 weeks old
- Weight at study initiation:
Males: 252-257 g; Females: 178-182 g; The initial body weight variation did not exceed ± 20% of the mean weight for each sex.
- Fasting period before study: None
- Housing:
Dose-range finding study:
During the study the animals were housed in groups of 2/sex in macrolon cages type 1290D (425x266x150 mm) with sterilized wood shavings (Woody Clean) as bedding material and environmental enrichment (shreds of paper).
Main study:
During the premating period, the animals were housed in groups of 4/sex in macrolon cages type 1400U (480x375x210 mm) with sterilized wood shavings (Woody Clean) as bedding material and environmental enrichment (shreds of paper). For mating, one male and one female were housed together in type 1290D cages. Mated females were housed individually in type 1290D cages, which will be placed in another cage rack.
- Diet:
The rats were fed a commercial rodent diet ad libitum (Rat & Mouse No. 3 Breeding Diet, RM3). Each batch of RM3 diet is analysed by the supplier (SDS Special Diets Services, Witham, England) for nutrients and contaminants. The certificate(s) of analysis pertaining to the batch(es) used in this study was included in the study report. The feed was provided as a powder, in stainless cans, covered by a perforated steel plate that serves to prevent spillage. The feed in the feeders was refreshed once per week, unless the stability of the test substance in the diet dictated more frequent refreshing.
- Water:
The drinking water (tap-water) was supplied ad libitum in polypropylene bottles, which was cleaned at least weekly and filled up when necessary.
- Acclimation period:
Upon arrival, the rats were quarantined and checked for overt signs of ill health and abnormalities. During the quarantine period serological examinations of the microbiological status of the rats was conducted in a random sample. If the results of serology are satisfactory, the rats will be transferred to their experimental room and acclimatized to the laboratory conditions for at least 5 days prior to the experimental start date.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): At least 30% and not exceeding 70%
- Air changes (per hr): The room will be ventilated with about 10 air changes per hour
- Photoperiod (hrs dark / hrs light): Lighting will be artificial with a sequence of 12 hours light and 12 hours dark.

Administration / exposure

Route of administration:
oral: feed
Details on route of administration:
-
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:
The test substance will be incorporated in the basal diet by mixing in a mechanical blender.

DIET PREPARATION
- Rate of preparation of diet (frequency): The experimental diets will be prepared once shortly before the start of the studies, unless the results of the stability analyses dictate more frequent preparation. The feed in the feeders will be refreshed daily.
- Mixing appropriate amounts with (Type of food): In the main study, rats were fed diets containing 0, 5, 30 and 200 mg dibutyldichlorostannane/kg diet for 28 days (males) or during 2 weeks premating, mating, gestation and up to postnatal day 4 - 6 (females). (Rat & Mouse No. 3 Breeding Diet, RM3)
- Storage temperature of food: The test substance DBTC was considered to be stable in the diets upon storage at room temperature for 1 day (but not for 4 days and 7 days) and upon storage at < -18 °C for 6 weeks, with the exception of the 270 mg/kg dose level, which was considered to be stable in the diets upon storage at < -18 °C for at least 24 days.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
From each diet sample, 2.0 g was transferred into a 50 ml Greiner tube.
An aliquot of the internal standard solution (monoheptyltin trichloride, diheptyltin dichloride, tripropyltin chloride and tetrapropyltin in methanol) was added. Subsequently methanol, acetate buffer solution (pH 4.5), 20% aqueous sodium tetraethylborate (NaBEt4) solution and hexane (with naphthalene as internal standard) were added to each sample and this mixture was shaken and heated to 60 °C. During this step, the organotin chlorides were converted into the corresponding ethylated tetraorganotin derivatives, which were extracted into the hexane layer. Prior to GC-MS analysis, the hexane layer was washed with 2 mol/l HCl in order to remove (most of) the ethylboron compounds that interfere with the GC-MS analysis. The concentration of each test substance in feed was determined by GC-MS analysis of the hexane extracts.
Duration of treatment / exposure:
The animals were fed diets containing test substance from the start of the treatment period until sacrifice.
In the main study, rats were fed diets containing 0, 5, 30 and 200 mg dibutyldichlorostannane/kg diet for 28 days (males) or during 2 weeks premating, mating, gestation and up to postnatal day 4 - 6 (females).
Frequency of treatment:
Daily in feed.
Doses / concentrationsopen allclose all
Dose / conc.:
5 mg/kg diet
Remarks:
Doses / Concentrations:
5 mg/kg
Basis:
nominal in diet
Dose / conc.:
30 mg/kg diet
Remarks:
Doses / Concentrations:
30 mg/kg
Basis:
nominal in diet
Dose / conc.:
200 mg/kg diet
Remarks:
Doses / Concentrations:
200 mg/kg
Basis:
nominal in diet
No. of animals per sex per dose:
12 males and 12 females (24 in total per dose group)
Control animals:
yes, plain diet
Details on study design:
- Dose selection rationale:
The dose levels were selected in consultation with the sponsor and were based on the results of the dose-range finding study conducted at 0, 30, 90, 270 and 1080 mg/kg test material/diet.
- Rationale for animal assignment:
Shortly before the start of the studies, the animals (males and females separately) were allocated to the various treatment groups by computer randomization and proportionally to body weight
Positive control:
NDA

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule:
Each animal was observed daily in the morning hours by cage-side observations and, if necessary, handled to detect signs of toxicity starting from the beginning of the study. On working days, all cages were checked again in the afternoon for dead or moribund animals to minimise loss of animals from the study. On Saturdays, Sundays and public holidays only one check per day was carried out. All abnormalities, signs of ill health or reactions to treatment were recorded.
- Cage side observations: No mortalities were observed.
No clinical signs were observed in the male and female animals from the start of the study until sacrifice.


BODY WEIGHT: Yes
- Time schedule for examinations:
Body weights of male and female rats were recorded on day -2 (randomization) and on days 0 (first day of dosing), 7 and 14 of the premating period.
Males were weighed weekly during the mating period until sacrifice. Females were weighed during mating (day 0, 7 and 14) and mated females were weighed on days 0, 7, 14 and 21 during presumed gestation and on day 1 and 4 of lactation. All animals were weighed on the day of sacrifice.


FOOD CONSUMPTION AND COMPOUND INTAKE:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
The test substance intake of the male animals of the low-, mid-, and high-dose groups was respectively:
Premating period
days 0-7 0.4, 2.3 and 12.8 mg/kg body weight/day,
days 7-13 0.3, 2.1 and 13.0 mg/kg body weight/day.
After mating
days 21-28 0.3, 1.9 and 10.4 mg/kg body weight/day,

The test substance intake of the female animals of the low-, mid-and high-dose groups was respectively:
Premating period
days 0-7: 0.4, 2.0 and 12.0 mg/kg body weight/day,
days 7-13: 0.3, 2.0 and 12.5 mg/kg body weight/day,
Gestation period
GD 0-7: 0.4, 2.4 and 15.4 mg/kg body weight/day,
GD 7-14: 0.4, 2.4 and 14.1 mg/kg body weight/day,
GD 14-21: 0.3, 2.1 and 12.6 mg/kg body weight/day,
Lactation period
PN 1-4: 0.3, 1.7 and 6.2 mg/kg body weight/day.
Sacrifice and pathology:
- Parental animals:
SACRIFICE
- Male animals: Male animals were sacrificed on day 28.
- Maternal animals: Female animals with a litter were sacrificed on PN 4 to 6.

GROSS NECROPSY
All animals were subjected to a complete gross necropsy.
Samples of the following tissues and organs of all parent animals were preserved in a neutral aqueous phosphate-buffered 4% solution of formaldehyde; except for the testes which were preserved in Bouin's fixative:
- ovaries
- uterus (after counting the implantation sites)
- testes*
- epididymides*
- seminal vesicles
- prostate
- thymus* (female animals only)
- organs and tissues showing macroscopic abnormalities
*Organs were weighed (paired organs together) as soon as possible after dissection to avoid drying.

HISTOPATHOLOGY / ORGAN WEIGHTS
The animals were euthanized by exsanguination under CO2/O2-anaesthesia and then examined grossly for pathological changes.
At necropsy the following organs were weighed:
kidney
liver
spleen
testes
thymus
brain

- Offspring:
SACRIFICE
Pups were examined externally for gross abnormalities and killed by hypothermia at <-18°C on PN 4 or shortly thereafter.

GROSS NECROPSY
A necropsy was performed on stillborn pups and pups that died during the study; macroscopic abnormalities were recorded.
Other examinations:
Sperm parameters (Parental animals)
Parameters examined in male parental generations:
No abnormalities were detected in the Prostate, Seminal, Vesicle and Testes of any males

Litter observations
PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
Number and sex of pups, stillbirths, live births, pup mortality, pup observations and pathology of pups.

GROSS EXAMINATION OF DEAD PUPS:
A necropsy was performed on stillborn pups and pups that died during the study; macroscopic abnormalities were recorded. Pups were examined externally for gross abnormalities and killed by hypothermia at <-18°C on PN 4 or shortly thereafter.
Statistics:
Statistics
The resulting data was analyzed using the methods mentioned below. Other statistical tests may be performed when considered appropriate. As a level of significance will be considered: p< 0.05.
- Clinical findings will be evaluated by Fisher's exact probability test.
- Body weight, body weight gain, organ weights and food consumption data will be subjected to one-way analysis of variance (ANOVA) followed by Dunnett's multiple comparison tests.
- Fisher's exact probability test will be used to evaluate the number of mated and pregnant females and females with live pups.
- Number of implantation sites, live and dead pups will be evaluated by
Kruskal- Wallis nonparametric analysis of variance followed by the MannWhitney U-test.
Histopathological changes: Fisher's exact probability test.

Reproductive indices
- pre-coital time = time between the start of mating and successful copulation
- duration of gestation = time between gestation day 0 and day of delivery
- mating index = (number of females mated/number of females placed with males) x 100
- male fertility index = (number of males that became sires/number of males placed with females) x 100
- female fertility index = (number of pregnant females/number of females placed with males) x 100
- female fecundity index = (number of pregnant females/number of females mated) x 100
- gestation index = (number of females with live pups/number of females pregnant) x 100

Offspring viability indices
- live birth index = (number of pups born alive/number of pups born) x 100
- pup mortality day n = (number of dead pups on day n/total number of pups on day n) x 100
- sex ratio day n = (number of live male pups on day n/ number of live pups on day n) x 100
- number of lost implantations = number of implantations sites - number of pups born alive
- post-implantation loss = [(number of implantation sites - number of pups born alive)/number of implantation sites] x 100

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Description (incidence and severity):
-
Mortality:
no mortality observed
Description (incidence):
-
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
-
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
-
Food efficiency:
not examined
Description (incidence and severity):
-
Water consumption and compound intake (if drinking water study):
not examined
Description (incidence and severity):
-
Ophthalmological findings:
not examined
Description (incidence and severity):
-
Haematological findings:
not examined
Description (incidence and severity):
-
Clinical biochemistry findings:
not examined
Description (incidence and severity):
-
Urinalysis findings:
not examined
Description (incidence and severity):
-
Behaviour (functional findings):
not examined
Description (incidence and severity):
-
Immunological findings:
effects observed, treatment-related
Description (incidence and severity):
-
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
-
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
-
Neuropathological findings:
not examined
Description (incidence and severity):
-
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
-
Histopathological findings: neoplastic:
not specified
Description (incidence and severity):
-
Other effects:
not specified
Description (incidence and severity):
-
Details on results:
- Parental results:

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
No mortalities were observed.
No clinical signs were observed in the male and female animals from the start of the study until sacrifice.


Target organ toxicity disccused / summerizied under effect leffels (cp IUCLID 5)

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
Mean body weight of the male animals of the high-dose group was statistically significantly decreased from day 14 until sacrifice on day 28 of the study. Body weight change of the male animals of the high-dose group was statistically significantly decreased during the entire study and in the animals of the mid-dose group from days 14-21. Body weight change was increased in the male animal of the low- and mid-dose groups from days 0-7. This finding was considered as a incidental finding of no toxicological relevance.
During the premating, gestation and lactation periods, the mean body weight and body weight change of the female animals of the high-dose group was decreased when compared to the control group. Statistical significance for the difference in body weight was observed on day 14 of the premating period, the entire gestation period and during the lactation period on PN 4. Statistical significance for the difference in body weight change was observed from days 0-7 of the premating period and during the gestation days 7-14 and 14-21.
Mean food consumption of the male animals of the high-dose group was decreased; statistical significance was only reached when food consumption was expressed as g/animal/day from days 7-14 of the premating period.
During the premating period food consumption (expressed as g/animal/day and g/kg body weight/day) of the female animals of the high-dose group was statistically significantly decreased from days 0-7, during the entire gestation period and during the lactation period from PN 1-4 (expressed as g/animal/day and g/kg body weight/day). Food consumption of the animals of the low- and mid-dose groups was comparable to the control group.

TEST SUBSTANCE INTAKE (PARENTAL ANIMALS)
The test substance intake of the male animals of the low-, mid-, and high-dose groups was respectively:
Premating period
days 0-7 0.4, 2.3 and 12.8 mg/kg body weight/day,
days 7-13 0.3, 2.1 and 13.0 mg/kg body weight/day.
After mating
days 21-28 0.3, 1.9 and 10.4 mg/kg body weight/day,

The test substance intake of the female animals of the low-, mid-and high-dose groups was respectively:
Premating period
days 0-7: 0.4, 2.0 and 12.0 mg/kg body weight/day,
days 7-13: 0.3, 2.0 and 12.5 mg/kg body weight/day,
Gestation period
GD 0-7: 0.4, 2.4 and 15.4 mg/kg body weight/day,
GD 7-14: 0.4, 2.4 and 14.1 mg/kg body weight/day,
GD 14-21: 0.3, 2.1 and 12.6 mg/kg body weight/day,
Lactation period
PN 1-4: 0.3, 1.7 and 6.2 mg/kg body weight/day.


REPRODUCTIVE FUNCTION: ESTROUS CYCLE (PARENTAL ANIMALS)
nda

REPRODUCTIVE FUNCTION: SPERM MEASURES (PARENTAL ANIMALS)
Male animals were sacrificed on day 28. Terminal body weight was statistically significantly decreased in the males of the high-dose group. No relevant treatment-related observations in organ weight and microscopic examination of the reproductive organs were observed.

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
One female of the low-dose group was not mated at the end of the mating period. Pre-coital time was comparable for the control and dibutyldichlorostannane-treated groups. The number of pregnant females, the number of males that became sires amounted 9, 8, 7 and 7 for the control, low-, mid- and high-dose groups, respectively.
The number of females with liveborn pups was 9, 8, 7 and 3 for the control, low-, mid-and high-dose groups, respectively.
The mating index ranged from 92-100%.
The female fecundity index, female fertility index and male fertility index were comparable among the control and dibutyldichlorostannane-treated groups.
The gestation index was 100 % in the control, low- and mid-dose groups.
The live birth index was 99, 99,and 94% in the control, low- and mid-dose groups, respectively.
In the high-dose group, the gestation index and the live birth index were decreased (43 and 56%, respectively).
Stillborn pups were observed in 1, 1, 3, and 3 litters of the control, low-, mid- and high-dose group, respectively.
During the observation period no females with all still born pups were noted.
However, at necropsy, females D173, D179, D183 and D185 appeared to be pregnant and 3 of these females appeared to have autolytic fetuses and resorptions (noted as late resorptions) in the uterus.
In one female D179 only implantation sites were observed; this female probably delivered overnight and immediately cannabilized her pups.
Post-implantation loss was 13.4, 7.5, 20.4 and 87.6% for the control, low-, mid- and high-dose groups, respectively.

ORGAN WEIGHTS (PARENTAL ANIMALS)
Male animals were sacrificed on day 28. In the males of the high-dose group terminal body weight was statistically significantly decreased. Relative testes weight of the male animals of the high-dose group was statistically significantly increased; this finding was the result of the decreased terminal body weight and therefore of no toxicological significance.
Female animals with a litter were sacrificed on PN 4 to 6. Terminal body weight of the female animals of the high-dose group was statistically significantly decreased. The absolute and relative thymus weight of the high-dose groups was statistically significantly decreased. Furthermore, the relative thymus weight of the females of the mid-dose group was statistically significantly decreased whereas the absolute thymus weight of females of this group was not statistically significantly decreased compared to the thymus weight of the females of the control group (absolute thymus weight mid-dose 0.080 versus 0.124 g control). No effect on thymus weight was observed in the females of the low-dose group.

GROSS PATHOLOGY (PARENTAL ANIMALS)
At necropsy an increased incidence of late resorption of foetuses was seen in the uteri of three (out of seven pregnant) high-dose females.
The remaining macroscopic observations are common findings in rats of this strain and age and occurred only incidentally.
The decreased size of the thymus was not reported as a gross lesion as decreases in thymus weights were considered to reflect the diminished size of the thymus in individual animals more accurately.

HISTOPATHOLOGY (PARENTAL ANIMALS)
In the present study only reproductive organs and, in females, thymuses were examined microscopically.
Examination of the thymus revealed severe to very severe lymphoid depletion in 12/12 high-dose females, and moderate to severe lymphoid depletion in 6/12 (pregnant) mid-dose females (no lymphoid depletion of the thymus was observed in all 5 non-pregnant and one pregnant female).
Lymphoid depletion was characterized by a decrease in the size of the thymic lobules because of an extensive loss of cortical and medullary small lymphocytes. Consequently the distinction between the cortical and medullary areas was blurred. In the (very) severe cases the cortex was very small, or partially absent. The remaining lymphoid cells visible in the cortical areas were mainly lymphoblasts. Lymphoblastic cells and reticular epithelial cells had increased, and/or greater numbers of these cells were visible because of the disappearance of small lymphocytes and collapse of thymic stroma.
Examination of the ovaries revealed a statistically significant increase in the incidence of cysts in nine high-dose females.
The remaining histopathological observations are common findings in rats of this strain and age. The lesions occurred only in a few animals, and the incidence of these lesions was comparable in the treated groups and control.

- Offspring results:

VIABILITY (OFFSPRING)
Pup mortality in the highest dose was 50 % compared to 5% in the control group.

CLINICAL SIGNS (OFFSPRING)
The incidence of runts (pup weight less than mean pup weight of the control group minus 2 standard deviations) in the high-dose group was statistically significantly increased on PN 1 and 4. No statistically significant difference was observed between the other dibutyldichlorostannane-treated groups and the control group. The other findings were normal for pups of this age and are considered not to be related to treatment.

BODY WEIGHT (OFFSPRING)
The pup weight on PN 1 and 4 of the high-dose group was statistically significantly decreased. Pup weight change of the pups of this group between PN 1-4 was not statistically significantly decreased. No effect on pup weight and pup weight change was observed in the other dibutyldichlorostannane-treated groups when compared to the control group.

SEXUAL MATURATION (OFFSPRING)
n/a

ORGAN WEIGHTS (OFFSPRING)
n/a

GROSS PATHOLOGY (OFFSPRING)
Macroscopic observation of the stillborn pups revealed 1 pup with a missing tailtip in the high-dose group. In addition some pups (mid- and high-dose groups) were autolytic and 1 pup of the mid-dose group was partly cannibalized.

HISTOPATHOLOGY (OFFSPRING)
n/a

OTHER FINDINGS (OFFSPRING)
Although the number of pups delivered in the high-dose group was substantially lower than in the control group no statistical significance was observed for this observation; the number of pups delivered amounted 11.3, 10.6, 11.4 and 6.0 for the control, low-, mid- and high-dose groups, respectively.
The number of liveborn pups amounted 101, 84, 75 and 10 for the control, low-, mid- and high-dose groups, respectively.
The number of stillborn pups was 1, 1, 5 and 8 for the control, low-, mid- and high-dose groups, respectively.
Pup mortality on PN 1 was 1.0, 1.2, 6.3 and 44.0% in the control, low-, mid- and high-dose groups, respectively.
Pup mortality on PN 4 amounted 5, 1, 8 and 5 (incidences: 5.0, 1.2, 11.0 and 50.0%) in the control, low-, mid- and high-dose groups, respectively.
No litters were lost entirely between PN 0-4.
The number of live pups per litter on PN 1 amounted 11.2, 10.5, 10.7 and 3.3 for the control, low-, mid- and high-dose groups, respectively) and on PN 4 the number of live pups per litter amounted 10.7, 10.4, 9.6 and 1.7 for the control, low-, mid- and high-dose groups, respectively.
No difference was observed in the sex ratio between the groups.

Effect levels

open allclose all
Key result
Dose descriptor:
NOAEL
Remarks:
(general toxicity)
Effect level:
> 0.3 - < 0.4 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: based on the observed effects in the high- and mid-dose animals (decreased weight and microscopic findings in the thymus of the female animals).
Key result
Dose descriptor:
NOAEL
Remarks:
(reproductive effects)
Effect level:
> 1.9 - < 2.3 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male
Basis for effect level:
food efficiency
Dose descriptor:
NOAEL
Remarks:
(reproductive effects)
Effect level:
> 1.7 - < 2.3 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
other: -

Target system / organ toxicity

Key result
Critical effects observed:
no
Lowest effective dose / conc.:
0.3 mg/kg bw/day (nominal)
System:
immune system
Organ:
other: based on the observed effects in the high- and mid-dose animals (decreased weight and microscopic findings in the thymus of the female animals).
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
yes

Any other information on results incl. tables

The following significant effects on reproduction and litter data were observed in the high-dose group when compared to the control group:

  High dose Control
number of females pregnant no delivery       4.0 0.0
number of females with liveborn pups        3.0 9.0
gestation index (%)                          43.0 100.0
post-implantation loss (%)                     87.6 13.4
number of pups delivered                            6.0 11.3
number of liveborn pups                         10.0 101.0
number of live pups/litter PN 1                3.3 11.2
number of live pups/litter PN  1.7 10.7
number of stillborn pups    8.0 1.0
pup mortality PN 4 (%)  50 5
pup weight PN 1(g)                                      4.4 5.6
pup weight PN 4 (g)                             6.0 8.0
percentage of runts PN 1 (%)  80.0 5.9
percentage of runts PN 4 (%) 40.0 4.2

No effect on reproduction and litter data was observed in the low- and mid-dose group.

Female animals with a litter were sacrificed on PN 4 to 6. Three females showed late resorptions (autolytic fetuses) in the uterus.

Applicant's summary and conclusion

Conclusions:
Based on the observed effects in the high- and mid-dose animals (decreased weight and microscopic findings in the thymus of the female animals, the NOAEL for general toxicity is established on the low-dose level (5 mg/kg diet which is equivalent to 0.3-0.4 mg/kg body weight/day for the male and female animals).
In view of the reproductive effects observed in the high-dose group, the NOAEL for reproductive toxicity was established at the mid-dose level (30 mg/kg diet which is equivalent to 1.9-2.3 mg/kg body weight/day in the male animals and 1.7-2.4 mg/kg body weight/day in the female animals).
Executive summary:

In the Reproduction/developmental toxicity screening test in rats (TNO study number: V 4906) the test material was determined to have a NOAEL for general toxicity established on the low-dose level of 5 mg/kg diet and the NOAEL for reproductive toxicity was established at the mid-dose level of 30 mg/kg diet.

The study was performed in accordance with the OECD Guideline for Testing of Chemicals no. 421 (adopted 27 July 1995). and was carried out in accordance with the OECD Principles of Good Laboratory Practice (as revised in 1997). No mortalities were observed. No clinical signs were observed in the male and female animals from the start of the study until sacrifice. Examination of the thymus revealed severe to very severe lymphoid depletion in 12/12 high-dose females, and moderate to severe lymphoid depletion in 6/12 (pregnant) mid-dose females.

Three females showed late resorptions (autolytic fetuses) in the uterus during necropsy.