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Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
12 November 2003 to 8 March 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study was conducted in accordance with the standardised testing guideline OECD 422 and in accordance with GLP with no deviations thought to affect the quality of the presented data. The study was reported to a high standard, sufficient to assess the reliability of the data presented.
Cross-referenceopen allclose all
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report date:
2006

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Limit test:
no

Test material

Constituent 1
Reference substance name:
Dioctyltin oxide
EC Number:
212-791-1
EC Name:
Dioctyltin oxide
Cas Number:
870-08-6
Molecular formula:
C16H34OSn
IUPAC Name:
Stannane, dioctyloxo-
Test material form:
solid: particulate/powder
Details on test material:
- Name of test material (as cited in study report):Dioctyloxostannane (DOTO), Dioctyltin oxide
- Physical state: Powder, white
- Storage condition of test material: < - 18 °C in the dark

Test animals

Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Age at study initiation: 10-11 weeks
- Weight at study initiation: The weight variation of the animals for each sex did not exceed 20 %.
- Diet: ad libitum
- Water: tap water ad libitum in polypropylene bottles

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-25 °C
- Humidity (%): 30-70 5
- Air changes (per hr): 10 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours light and 12 hours dark

DOSE-RANGE FINDING TEST IN-LIFE DATES: From: 12 November 2003 To: 26 November 2003
MAIN TEST IN-LIFE DATES: From: 14 January 2004 To: 8 March 2004

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on exposure:
DIET PREPARATION
- Rate of preparation of diet (frequency): The experimental diets were prepared once shortly before the study
- Mixing appropriate amounts with (Type of food): The test substance was weighed and placed in a small grinder. The tray was rinsed with food which was then also added to the grinder and mixed for 2 x 30 seconds. This mixture was moved to a Stephan cutter and the grinder was rinsed with food and moved to the cutter. Approximately 3 kg weighed food was mixed into the cutter for 2 x 2 minutes and moved. This was then moved to the Lödige cutter. The Stephan cutter was rinsed with approximately 3 kg of food and that was also moved to the Lödige cutter. Mixing was continued in the Lödige cutter for 2 minutes with the total amount of food.
- Storage temperature of food: <-18 °C
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The feed was checked for homogenous distribution, stability and concentration of the test substance for all the doses in the dose-range finding study. The same dose preparation for the dose-range finding study was also used for the main test. The homogenous distribution and achieved concentration of the low dose in the main test was also analysed.
Directly after preparation of the diet for the dose-range finding study, samples for homogeneity and stability were taken. Five samples were taken (approximately 50 g each) to examine the homogeneity of the dose from the top centre, middle centre, bottom centre, left centre and right centre of the mixer. Secondly samples (around 50 g) were taken from the top centre part of the mixer to measure the stability. The samples taken for measurement of the homogeneity were also used for dose confirmation. In addition the content (achieved concentration) of the test substance in the batch of diet used in the main study. Diet samples were taken for analysis immediately after preparation and stored at – 18 °C.
Samples of the 0, 25, 75, 200 and 500 mg/kg diets from the dose-range finding study and doses of 0, 25 and 250 mg/kg from the main study as well as all related calibration samples were derivatised.
A calculated amount of internal standard solution (MHT, DHT and TTPT in methanol) was added to 2.0 g of diet in a 50 mL Corning tube. 10 mL of 100 % acetic acid was then added and the Corning tube was closed and shaken for 60 minutes (250 rpm). 10 mL of acetate buffer solution (pH 4.5) was added along with 10 mL methanol. 2.0 mL of 20 % (m/V) aqueous STEB solutions was added, followed by 10 mL hexane (containing naphthalene, approximately 0.1 mg/L). The tube was shaken for 15 minutes (250 rpm) then placed in an oven at 60 °C for 15 minutes. After phase separation, the hexane layer (approximately 3 mL) was removed and washed with 3 mL of 2 mol/L HCl (30 minutes shaking at 250 rpm). The hexane top layer was diluted with hexane: hexane extracts from sample with dose levels of 0, 25 and 75 mg/kg were diluted five times, the higher doses were diluted fifty times. The resulting solutions were transferred into an amber coloured glass vial and anaylysed using GC-MS.
The procedure for the samples from the main study at doses of 0 and 5 mg/kg followed the same derivatisation procedure, except the initial quantity of the diet was 5.0 g not 2.0 g
The concentration of organotin compounds in the extracts was determined using GC-MS. For calculation of the amount of DOTO in the samples, the peak area of DHT was used as an internal standard. Quantitiation was achieved using the calibration graphs constructed from the calibration solutions.
The following conditions were used:
- Column: Fused silica HP5 MS, 30 m, 0.25 mm ID, 0.25 µm film
- Precolumn: fused silica HP5 MS, 2.5 m, 0.25 mm ID, 0.25 µm film
- Column temperature: after 3 minutes at 45 °C at a rate of 5 °C/min to 80 °C; then at a rate of 15 °C/min to 260 °C; 15 min at 260 °C.
- Carrier: helium; 1.5 mL/min constant flow
- Injection volume: 1 µL
- Injection temperature: start at 60 °C, then at a rate of 14.5 °C/s to 300 °C; 5 min at 300 °C
- Injection method: splitless
- Ionisation: electron impact 70 eV
- Mass range: 60-600 amu
- Mass fragments used: DOT m/z = 375*; 263; 151, DHT 347*; 249; 179
Mass fragments marked with an asterisk were used for quantitation
Details on mating procedure:
- M/F ratio per cage: 1:1
- Length of cohabitation: Until pregnancy occurred
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy
- After successful mating each pregnant female was caged individually
Duration of treatment / exposure:
Treated food was available ad libitum
Frequency of treatment:
Daily
Duration of test:
28 days
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (nominal)
Remarks:
Main study
Dose / conc.:
5 mg/kg bw/day (nominal)
Remarks:
Main study
Dose / conc.:
25 mg/kg bw/day (nominal)
Remarks:
Main study
Dose / conc.:
250 mg/kg bw/day (nominal)
Remarks:
Main study
Dose / conc.:
0 mg/kg bw/day (nominal)
Remarks:
Range finding test
Dose / conc.:
75 mg/kg bw/day (nominal)
Remarks:
Range finding test
Dose / conc.:
25 mg/kg bw/day (nominal)
Remarks:
Range finding test
Dose / conc.:
250 mg/kg bw/day (nominal)
Remarks:
Range finding test
Dose / conc.:
500 mg/kg bw/day (nominal)
Remarks:
Range finding test
No. of animals per sex per dose:
22 males and 22 females in the 14-day dose range finding study (5 groups of 4 male and 4 female rats)
52 males and 52 females in the main study (4 groups of 12 male and 12 female rats)
Control animals:
yes, plain diet
Details on study design:
- Dose selection rationale: Doses were selected on the results of the range finding test
- Rationale for animal assignment: Randomised

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Every morning throughout the study, and a second observation in the afternoon of working days.
- Cage side observations were included.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Prior to the first exposure and then once weekly

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights of male and female rats were taken on day -2 (randomisation) and on days 0 (first day of dosing), 7 and 13 of the premating period.
Males were weighed weekly during the mating period until sacrifice. Females were weighed during mating (day 0, 7 and 13) and mated females were weighed on day 0, 7, 14 and 21 during presumed gestation and on day 1 and 4 of lactation. All animals were weighed at sacrifice.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, also calculated as g/animal/day

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of the premating period
- Anaesthetic used for blood collection: Yes, CO2/02 anaesthesia
- Anit-coagulant: K2-EDTA
- Animals fasted: Yes, overnight
- How many animals: 5 rats/group
- Parameters checked:
Haemoglobin
Packed cell volume
red blood cell count
reticulocytes
Total white blood cell count
Prothrombin time
Thrombocyte count
Mean corpuscular volume (MCV)
Mean corpuscular haemoglobin (MCH)
Mean corpuscular haemoglobin concentration (MCHC)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of the premating period
- Anaesthetic used for blood collection: Yes, CO2/02 anaesthesia
- Animals fasted: Yes, overnight
- How many animals: 5 rats /group
- Parameters checked:
Fasting glucose
Alkaline phosphatase activity (ALP)
Aspartate aminotransferace activity (ASAT)
Alanine aminotransferace activity (ALAT)
Gamma glutamyl transferase activity (GGT)
Total protein
Albumin
Ratio albumin to globulin
Urea
Creatinine
Bilirubin (total)
Cholesterol (total)
Triglycerides
Phospholipids
Calcium (Ca)
Sodium (Na)
Potassium (K)
Chloride (Cl)
Inorganic phosphate

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Arena testing was performed prior to the first exposure and then once weekly until the end of dosing and in females until the end of lactation. Males and females selected for the functional observation battery test (FOB) and spontaneous activity measurements were excluded from the final arena testing.
At the end of the study, FOB test and spontaneous motor activity measurements were performed on day 27 for males and on post natal day for for females.
- Dose groups that were examined: All animals were subject to the arena testing. For the other two tests, 5 animals were randomly selected from each dose group.
- Battery of functions tested:
Autonomic: lacrimation, salivation, pupil response to light, palpebral closure, piloerection, defecation and urination
Neuromuscular: gait, mobility, forelimb and hindlimb gripstrength, landing foot splay, righting reflex
Sensorimotor: response to tail pinch, click, tough and approach of a visual object
Convulsive: clonic and tonic movements
Excitability: ease of removal, handling reactivity, arousal and vocalisations
Activity: rearing and motor activity
Physiological: body temperature

SACRIFICE
- Maternal animals: Sperm positive females that were not pregnant were killed 25 days after copulation, mothers with litters were killed on post natal day 4.

GROSS PATHOLOGY: Yes
The following were taken from all animals:
Ovaries
Uterus
Organs and tissues showing macroscopic abnormalities
The following were taken from 5 rats/group:
Adrenals
Axillary lymph node
Bone marrow (femur)
Brain
Caecum
Coagulation glands
Colon
Duodenum
Eyes
Heart
Jejunum
Lungs
Kidneys
Liver
Mammary gland (females only)
Mesentric lymph node
Parathyroids
Peyer's patches
Pituitary
Rectum
Sciatic nerve
Spinal cord
Spleen
Stomach
Thymus
Thyroids
Trachea
Urinary bladder

The following organs were weighed:
Adrenals
Brain
Heart
Kidneys
Liver
Spleen
Thymus

HISTOPATHOLOGY: Yes Microscopic examination was performed on the collected organs of all rats in the control and high-dose group.
The liver and ovaria of females and the thymus of the male and female rats in the low and mid-dose groups were also evaluated
The following tissues, though collected were not subject to histopathological examination:
Coagulation glands
Mammary gland (females only)
In addition, reproductive organs of females that were non-mated or non-pregnant of the mid and low dose groups were microscopically examined.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Number of corpora lutea: Yes
- Number of implantations: Yes
Fetal examinations:
- External examinations: Yes: all still born pups and pups that died during lactation
Statistics:
Clinical findings and histopathological changes of the maternal animals were evaluated using Fisher’s exact probability test.
Number of implantation sites, live and dead pups were evaluated by Kruskal-Wallis nonparametric analysis of variance followed by the Mann Whitney U-test.
Bodyweight, bodyweight gain, organ weights, food consumption, red blood cell and coagulation variables, total white blood cell counts, absolute differential white blood cell counts, clinical chemistry values and organ weights were assessed by one-way ANOVA followed by Dunnett’s multiple comparison tests.
Reticulocytes and relative differential white blood cell counts were assessed using Kruskal-Wallis non-parametric ANOVA followed by Mann-Whitney U-tests.
The results of the functional observations were measured on different scales. Continuous measurements were analysed by one-way analysis of variance at each time point, if found to be statistically significant, a post-hoc group comparison was performed. Rank order data were analysed by Kruskal-Wallis analysis of variance at each test time point, followed by planned multiple comparisons between dose groups were a significant results occurred. Categorical data were assessed using Pearson chi-square analysis.
Motor activity data were assessed by one-way analysis of variance at each time point with a post-hoc group comparison performed on significant results.
All tests were two sided and the level of probability p<0.05 was considered as significant. Effects of treatment on habituation were analysed by repeated measures of analysis variance in five 6 minute time blocks. Statistical evaluations on pup variables were considered on a litter basis. Additional evaluations on a pup basis were performed to identify any specific dose-related effect that may have occurred.
Indices:
Sex ratio day n = (number of live male pups on day n/number of live pups on day n) x 100

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
adverse effects in the immune system (thymus)
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Immunological findings:
effects observed, treatment-related
Description (incidence and severity):
thymus
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
increase in liver weight, decrease of thymus weight
Gross pathological findings:
not specified
Neuropathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Other effects:
not specified

Maternal developmental toxicity

Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
not specified
Early or late resorptions:
no effects observed
Dead fetuses:
effects observed, non-treatment-related
Description (incidence and severity):
only with high maternal toxicity
Changes in pregnancy duration:
no effects observed
Changes in number of pregnant:
no effects observed
Other effects:
not specified
Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
CLINICAL SIGNS AND MORTALITY
One female in the high dose group was found dead on gestation day 24; this animal was pregnant and 11 dead foetuses were found in the uterus.
The only finding during the gestation period (gestation day 21) was a sparsely haired animal in the 250 mg/kg group. During the lactation period, sparsely haired animals were noted in the control (n = 1), 5 mg/kg (n = 1) and in the 250 mg/kg group (n = 1). No other findings were noted.

BODY WEIGHT AND WEIGHT GAIN
Mean bodyweights of the dams of the high-dose group was statistically significantly decreased on gestation day 21 (8.5% lower than controls) and post-natal day 1 (9.3% lower than controls). Mean bodyweight changes of the dams of the high-dose group were more markedly affected during pregnancy, as the overall mean weight gain for the control animals accounted to 74.31 g, whereas that in the high-dose animals it was only 51.43 g (approx. 31% lower); during gestation day 14 to 21, the reduction in mean weight gain in the high-dose animals attained statistical significance, compared to controls, and was approximately 52% lower. Bodyweights and bodyweight change of the dams of all the treated groups were comparable to the controls group at all other times of the study.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
During the gestation period and lactation period (gestation days 7-14 and 14-21 and post-natal days 1-4), food consumption (expressed as g/animal/day and g/kg bodyweight/day) of the dams in the high-dose group was significantly decreased. Considering the entire pregnancy period, high-dose animals ate approx. 13% less food than controls (in terms of g/kg/day), and approx. 24% less food than controls during the 4-day lactation period. No other treatment-related effects were observed.

- Females (listed as low, mid and high dose groups; 5, 25 and 250 mg/kg diet respectively)
premating days 0-7: 0.4, 1.7 and 17.4 mg/kg bodyweight/day
premating days 7-13: 0.3, 1.6 and 15.4 mg/kg bodyweight/day
gestation days 0-7: 0.4, 2.0 and 17.4 mg/kg bodyweight/day
gestation days 7-14: 0.4, 1.9 and 16.7 mg/kg bodyweight/day
gestation days 14-21: 0.3, 1.4 and 11.2 mg/kg bodyweight/day
Post-natal days 1-4: 0.5, 2.4 and 17.4 mg/kg bodyweight/day

HAEMATOLOGY
All treated groups were found to be comparable to controls

CLINICAL CHEMISTRY
Bilirubin (µmol/L) was found to be statistically significantly increased in the high-dose females. this finding were considered to be treatment related. Other effects such as the statistically significant increase in calcium in the 5 mg/kg group was not considered to be related to treatment. No other changes were observed.

NEUROBEHAVIOUR
No treatment-related effects were observed.

ORGAN WEIGHTS
The absolute and relative weight of the female animals of the high dose group was significantly decreased (-69 and -66%, respectively, compared to controls). In the mid-dose group the relative thymus weight was also statistically significantly decreased (-36% compared to controls).
In the female animals of the high-dose group, the relative kidney and liver weights were statistically significantly increased (+14 and +22%, respectively, compared to controls).
No other effects were observed.

GROSS PATHOLOGY
At necropsy, a decrease in thymic size was seen in all animals in the 250 mg/kg diet groups, 11 animals in the 25 mg/kg diet group, 7 animals in the 5 mg/kg diet group and 5 animals in the control group.
Examination of the female that was found dead revealed hydrothorax, haemorrhagic lungs, dilation of the vena cava and haemorrhagic discharge in the vagina, these were considered to be indicative of problems during parturition.

HISTOPATHOLOGY
Microscopic evaluation of the thymus revealed moderate to very severe lymphoid depletion in all animals of the 250 and 25 mg/kg diet groups. Lymphoid depletion was characterised by a decrease in the thymic lobules due to an extensive loss of cortical and medullary small lymphocytes. The distinction between the cortical and medullary areas was unclear. In the more extreme effects observed, the cortex was very small, or absent. The remaining lymphoid cells visible in the cortical areas were mainly lymphoblasts. Lymphoblastic cells and reticuloepithelial cells had increased, and/or higher numbers of these cells were visible due to the disappearance of small lymphocytes and the collapse of the thymic stroma. In 3 high-dose animals, lymphoid depletion was accompanied by lymphoid depletion in the PALS (periateriolar lymphocyte sheath areas) in the spleen. The macroscopically observed thymi in 5 control and 7 low dose females exhibited no microscopic abnormalities. In the thymi of the 2 control and 2 low dose females pregnancy/lactation involution was observed. The thymic lobules were decreased in size but exhibited normal structure with the histological appearance of age-involution. Increased glycomeric vacuolation, viz moderate versus very slight was seen in the liver of 4 high dose females and was considered to be a potential cause of the increased weight.
Examination of the reproductive organs revealed a statistically significant increased in the incidence of cysts in the ovaries of 8 high-dose females.

Effect levels (maternal animals)

Key result
Dose descriptor:
NOAEL
Effect level:
> 0.3 - < 0.5 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity

Maternal abnormalities

Key result
Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Reduction in number of live offspring:
effects observed, non-treatment-related
Description (incidence and severity):
only with high maternal toxicity
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
effects observed, non-treatment-related
Description (incidence and severity):
only with high maternal toxicity
External malformations:
not examined
Skeletal malformations:
not examined
Visceral malformations:
not examined
Other effects:
not specified
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
VIABILITY
The number of females with liveborn pups was 11, 11, 11 and 8 for the control, low, mid and high dose respectively.
One female was found dead in the high dose group on gestation day 24; the animal was pregnant and 11 dead foetuses were discovered in the uterus. Stillborn pups were observed in the high dose in three litters. In the high-dose group 1 female with all stillborn pups was observed.
Pre-implantation loss was 8.4. 2.2. 12.3 and 6.2% for the control, low-, mid- and high-dose groups and was considered comparable.
Pos-implantation loss was 9.8, 11.6, 7.5 and 38.7% for the control, low-, mid- and high-dose groups respectively. The post-implantation loss recorded in the high-dose group was considered to be statistically significantly increased.
The number of pups delivered per litter was comparable in all groups, 9.8, 10.8, 9.6 and 8.0 in the control, low-, mid- and high-dose groups respectively. The number of liveborn pups was 108, 129, 104 and 64 in the control, low-, mid- and high-dose groups and was considered to be statistically significantly decreased in the high dose group.
The number of stillborn pups in the control, low- and mid-dose groups were 0, in the high-dose group a statistically significant increase was noted, with 8 stillborns recorded (6 of these from the same litter, 1 each in two additional litters).
Pup mortality on post-natal day 4 (PN 4) was comparable in all groups except the high dose groups in which there was a statistically significant increase. 1, 2, 2 and 22 mortalities (incidences 0.9, 1.6, 1.9 and 34.0%) were recorded in the control, low-, mid- and high-dose groups respectively.
Only in the high-dose group, 3 litters were lost entirely between post-natal day 0 and 4.
The number of live pups per litter on PN 1 (9.8, 10.8, 9.6 and 8.0) and PN 4 (9.7, 10.6, 9.4 and 7.0), was not found to be statistically significantly different even though the number of live pups was decreased in the high-dose group and PN1 and 4.
No difference was observed in the sex ratio

CLINICAL SIGNS (OFFSPRING)
On post-natal day 1, the number of runts was statistically significantly increased in the 250 mg/kg diet group. No other treatment related abnormalities were recorded.

BODY WEIGHT (OFFSPRING)
On post-natal day 1 and 4, a statistically significant decrease in pup bodyweight in the high-dose group was recorded (day 1 mean value for males+females in the high dose group was 4.54 g, compared to 5.08 in the control group). The pup weight change (PN 1-4) was significantly decreased in the male pups of the high-dose group (mean body weight gain of 1.38 g, compared to 2.56 g in the controls). No effects were noted in the other treatment groups.

GROSS PATHOLOGY (OFFSPRING)
Macroscopic evaluation of the stillborn pups revealed 3 partially cannibalized pups and 3 autolytic pups in the high-dose group; the latter pups had no abnormalities. In addition 2 stillborn pups with no abnormalities in the high-dose groups were examined.

Effect levels (fetuses)

Key result
Dose descriptor:
NOAEC
Effect level:
> 25 mg/kg diet
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Viability index day 1-4
Remarks on result:
other: effects only with high maternal toxicity

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Table 1: Test material concentration in experimental diets

Nominal concentration (mg/kg)

Mean Nominal Measured Concentration (mg/kg)

Percent of Nominal

0 (#1)

<0.05

NA

0 (#2)

<0.05

NA

0 (#3)

<0.05

NA

5 (#1)

4.52

90

5 (#2)

4.93

99

5 (#3)

4.4

88

25 (#1)

24.9

100

25 (#2)

26.5

106

25 (#3)

26.3

105

250 (#1)

247

99

250 (#2)

240

96

250 (#3)

244

98

#3: repeated analysis of batch no. 2

 

Table 2: Summary of relevant treatment related findings

Parameter

Dose levels

5 mg/kg diet

25 mg/kg diet

250 mg/kg diet

Bodyweight: GD 21, PN 1 (females only)

 

 

Decreased

Bodyweight change: GD 14-21 (females only)

 

 

Decreased

Food consumption: PM 7-13 (males) GD 7-14, 14-21 and PN 1-4 (females only)

 

 

Decreased

Bilirubin (females only)

 

 

Increased

Alkaline phosphatase (males only)

 

 

Increased

Relative liver weight (females only)

 

 

Increased

Relative kidney weight (females only)

 

 

Increased

Absolute and/or relative thymus weight

 

Decreased

Decreased

Thymus: lymphoid depletion (males only)

 

 

Increased

Thymus: lymphoid depletion (females only)

 

Increased

Increased

Ovary: cysts (females only)

 

 

Increased

Liver: glycogenic vacuolation (females only)

 

 

Increased

Post-implantation loss

Increased

Number of stillborn pups

Increased

Pup mortality PN 4

Increased

Pup weight PN 1

Decreased

Number of runts PN 1

 

 

Increased

 

Table 3: Litter data (high dose group)

Parameter

High dose group

Control group

Number of females with liveborn pups

8

11

Post-implantation loss (%)

38.7*

9.8

Mean number of pups delivered

8.0

9.8

Mean number of live pups/litter PN1

8.0

9.8

Mean number of live pups/litter PN 4

7.0

9.7

Total number of stillborn pups

8*

0

Pup mortality PN 4 (%)

34*

0.9

Pup weight PN 1 (g)

4.5*

5.1

Pup weight PN 4 (g)

6.5

7.6

Percentage of runts PN 1 (%)

34*

2

* Statistically significantly different.

Applicant's summary and conclusion

Conclusions:
Based on the effects noted in the thymus in the 25 mg/kg diet groups, the NOAEL for general toxicity was concluded to be the lowest group tested, 5 mg/kg diet which was equivalent to 0.3-0.5 mg/kg bw/day.
A NOAEL for developmental toxicity was not considered necessary because the reproductive effects observed were non-specific and considered to be related to metarnal toxicity.
Executive summary:

The developmental effects of the test substance was assessed in a repeated dose toxicity and reproductive and developmental screening study in rats. The study was performed in accordance with GLP and to the standardised guideline OECD 422. Only one death was noted during the study.

Based on the effects noted in the thymus in the 25 mg/kg diet groups, the NOAEL for general toxicity was concluded to be the lowest group tested, 5 mg/kg diet which was equivalent to 0.3-0.5 mg/kg bw/day.

A NOAEL for developmental toxicity was not considered necessary because the reproductive effects observed were non-specific and considered to be related to metarnal toxicity.