Propylidynetrimethyl trimethacrylate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 02-Sep-2014 to 18-Mar-2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

adopted 22nd January 2001

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.31 (Prenatal Developmental Toxicity Study)

Version / remarks:

EC 2004/73 B31, dated April 29, 2004

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

Version / remarks:

EPA 712-C-98-207, dated August 1998

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: Japanese Guidelines (Ministry of Agriculture, Forestry and Fisheries, Test Data for Registration of Agricultural Chemicals, 12 Nohsan No. 8147, Teratology (2-1-18), Agricultural Production Bureau, dated November 24, 2000).

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Propylidynetrimethyl trimethacrylate

EC Number:

221-950-4

EC Name:

Propylidynetrimethyl trimethacrylate

Cas Number:

3290-92-4

Molecular formula:

C18H26O6

IUPAC Name:

2,2-bis[(methacryloyloxy)methyl]butyl methacrylate (non-preferred name)

Test material form:

liquid

Details on test material:

- Name of test material (as cited in study report): Propylidynetrimethyl trimethacrylate
- Substance type: Organic monoconstituent substance
- Physical state: Colourless to light yellow liquid

- Storage condition of test material: At room temperature (20 ± 5 °C) protected from sunlight

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories, B.V., Kreuzelweg 53, 5961 NM Horst / Netherlands
- Age at study initiation: 11 weeks at day 0 post coitum
- Weight at study initiation: 178 to 281 g at day 0 post coitum
- Fasting period before study: None
- Housing: Individually in Makrolon type-3 cages with wire mesh tops and standard softwood bedding (‘Lignocel’ J. Rettenmaier & Söhne GmbH & CoKG, 73494 Rosenberg / Germany, imported by Provimi Kliba SA, 4303 Kaiseraugst / Switzerland) with paper enrichment (Enviro-dri from Lillico, Biotechnology, Surrey / UK and ISO-BLOX from Harlan Laboratories B.V. / Netherlands).
- Diet: Pelleted standard Harlan Teklad 2018C (batch no. 13/14) rodent maintenance diet (Provimi Kliba SA, 4303 Kaiseraugst / Switzerland) was available ad libitum. The feed was analyzed for contaminants.
- Water: Community tap-water from Itingen was available ad libitum in water bottles. Bacteriological assay, chemical and contaminant analyses of respective samples were performed.
- Acclimation period: 7 days under test conditions after health examination. Only animals without any visible signs of illness were used for the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30 - 70
- Air changes (per hr): 10 - 15
- Photoperiod (hrs dark / hrs light): 12-hour fluorescent light / 12-hour dark cycle with at least eight hours music during the light period.

IN-LIFE DATES: From: 02-Sep-2014 (start of 7-day Acclimatization) To: 09-Oct-2014 (Last Necropsy)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The dose formulations were prepared weekly using the test item as supplied by the Sponsor.
The vehicle was pre-warmed to a temperature of approximately 40 °C. Propylidynetrimethyl trimethacrylate was weighed into a glass beaker on a tared precision balance and approximately 80 % of the warm vehicle was added (w/v). The mixture was homogenized using an electrical homogenizer until a clear to colloid-like yellowish solution was obtained. Having obtained a homogeneous mixture, the remaining vehicle was added until the required final volume. Separate formulations were prepared for each concentration.
Homogeneity of the test item in the vehicle was maintained during the daily administration period using a magnetic stirrer.
Stability and Storage of Dose Formulations: For at least 8 days at room temperature (20 ± 5 °C) based on stability results of Harlan Laboratories Study no. D84010 (Braun 2015, subchronic repeated oral toxicity

DIET PREPARATION
- Not relevant due to exposure via gavage

VEHICLE
- Justification for use and choice of vehicle: Considered non-toxic to the test animals and ability to form a homogeneous mixture with the test item
- Concentration in vehicle (nominal): 0, 25, 75 and 250 mg/mL (at 0, 100, 300 and 1000 mg/kg bw/day, respectively)
- Amount of vehicle (by gavage): 4 mL/kg body weight with a daily adjustment to the actual body weight
- Lot/batch no.: 453206485 (Source: Carl Roth GmbH + Co. KG, Karlsruhe/Germany, Expiry Date: 14-Jan-2016)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Representative samples were dispatched to the analytical laboratories internally (at room temperature) and stored frozen at -20 ± 5 °C until analysis.
The test item was used as the analytical standard.
Stock solutions of Propylidynetrimethyl trimethacrylate in acetonitrile were prepared for external calibration. For example, 34.77 mg of Propylidynetrimethyl trimethacrylate was weighed into a 50 mL volumetric flask and filled to about 75% of final volume with acetonitrile. The mixture was sonicated for at least five minutes and brought to volume with acetonitrile to yield a solution with a concentration of 695.4 µg/mL. Aliquots of this stock calibration solution were diluted with acetonitrile to obtain calibration solutions with nominal concentrations ranging from 10.43 to 99.44 µg/mL. On each occasion calibration solutions derived from two stock solutions were used for calibration.
Each sample was transferred into an appropriate volumetric flask. The sample vial was successively rinsed with at least two portions of tetrahydrofuran and the rinsings were combined in the volumetric flask. The flask was filled to about 75 % of the target volume with tetrahydrofuran and dissolution was achieved by sonication for at least five minutes. The flask was filled to the mark with tetrahydrofuran. Sample solutions were further diluted with acetonitrile into the calibration range.
Gas Chromatographic Conditions:
- Computerized System: EZ Chrom Elite; Agilent Technologies
- Column: BGB 1701 - BGB; 30 m x 0.25 mm; 0.25 µm
- Carrier Gas: Helium
- Temperature Gradient:
Rate [°C/min]; Temp. [°C]; Time [min]
0; 200; 0
10; 300; 5
- Running Time: 15 min
- Injector Temperature: 230 °C
- Injection Mode: Split ratio 5:1
- Flow: 1 mL/min (constant flow)
- Detector: FID; 250 °C (H2: 31; Air: 380; N2: 28 mL/min)
- Injection Volume: 2 µL
- Retention Time: Ca. 4.4 min
The linearity of the analytical system used for sample analyses was demonstrated with a good relationship between peak areas measured and calibration solution concentrations. All calibration points used met the acceptance limit of ±20 % variation from the calibration curve derived by linear regression analysis. The coefficients of determination (R²) were higher than 0.99.
The Propylidynetrimethyl trimethacrylate peak was assigned in sample chromatograms by comparison to that of calibration solutions. In blank sample chromatograms no peak appeared at the retention time of Propylidynetrimethyl trimethacrylate and, therefore, the absence of the test item in the vehicle control samples (corn oil) was confirmed.
The Propylidynetrimethyl trimethacrylate concentrations in the dose formulations ranged from 81.5 to 92.5 % with reference to the nominal and were within the accepted range of ±20 %. The homogeneous distribution of Propylidynetrimethyl trimethacrylate in the preparations was approved because single results found did not deviate more than 1.3 % from the corresponding mean and met the specified acceptance criterion of =15 %. Accordingly the effects were assigned to the nominal concentrations.

Details on mating procedure:

- Impregnation procedure: Cohoused, After acclimatization, females were housed with sexually mature males (1:1) in special automatic mating cages i.e. with synchronized timing to initiate the nightly mating period, until evidence of copulation was observed. This system reduced the variation in the copulation times of the different females. The females were removed and housed individually if the daily vaginal smear was sperm positive, or a copulation plug was observed. The day of mating was designated day 0 post coitum.
- M/F ratio per cage: 1:1
- Length of cohabitation: After 11 days (08 to 18-Sep-2014) pairing of all test animals was successfully completed.
- Further matings: No
- Verification of same strain and source of both sexes: Yes, all animals belonged to the RccHan™: WIST(SPF)
- Proof of pregnancy: Vaginal plug observed or sperm in vaginal smear referred to as day 0 of pregnancy
- Any other deviations from standard protocol: None

Duration of treatment / exposure:

15 days (during gestation period from day 6 to 20 post coitum)

Frequency of treatment:

Daily, at approximately 24 hour intervals

Duration of test:

21 days post coitum

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

100 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

300 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

1 000 mg/kg bw/day

No. of animals per sex per dose:

24 mated females per group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were selected based on a previous non-GLP dose range-finding study in Han Wistar rats, Harlan Laboratories non-GLP study no. D84021, using dose levels of 0, 100, 300 and 1000 mg/kg/day.
- Rationale for animal assignment: Computer-generated random algorithm

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily cage-side clinical observations (once daily, during acclimatization and up to day of necropsy). Viability / Mortality observation were made twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Daily from day 0 until day 21 post coitum.

FOOD CONSUMPTION: Yes
- Time schedule: For the following periods: days 0 - 3, 3 - 6, 6 - 9, 9 - 12, 12 - 15, 15 - 18 and 18 - 21 post coitum

WATER CONSUMPTION: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on day 21 post coitum
- Organs examined: Gross macroscopic examination of all internal organs

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Post mortem examination with emphasis on the uterus, uterine contents, corpora lutea count and position of foetuses in the uterus was performed and the data recorded.
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions (embryonic): Yes
- Number of late resorptions (foetal): Yes
- Other: The uteri (and contents) of all females with live foetuses were weighed during necropsy on day 21 post coitum to enable the calculation of the corrected body weight gain.

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: all per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: all per litter

Foetuses were removed from the uterus by caesarean section, sexed, weighed individually, examined for gross external abnormalities, sacrificed by a subcutaneous injection of sodium pentobarbital and allocated to one of the following procedures:
1. Microdissection technique (sectioning/dissection technique): Approximately one half of the foetuses from each litter were fixed in Bouin's fixative. They were examined by a combination of serial sections of the head and microdissection of the thorax and abdomen. This included detailed examination of the major blood vessels and sectioning of the heart and kidneys. After examination, the tissue was preserved in a solution of glycerin/ethanol (one foetus per container). Descriptions of any abnormalities and variations were recorded.
2. The remaining foetuses were eviscerated and with the exception of over the paws, the skin was removed and discarded. After fixation in ethanol, carcasses were processed through solutions of glacial acetic acid with Alcian blue (for cartilage staining), potassium hydroxide with Alizarin red S (for clearing and staining ossified bone) and aqueous glycerin for preservation and storage. The skeletons were examined and all abnormal findings and variations were recorded. The assessment included, but was not limited to all principal skeletal structures including cranium, vertebral column, rib cage and sternum, pectoral and pelvic girdles. The specimens were preserved individually in small containers.

The foetuses were sent to the contributing scientist for peer review at Huntingdon Life Sciences.

Statistics:

The following statistical methods were used to analyse food consumption, body weights, reproduction and skeletal examination:
• Means and standard deviations of various data were calculated and included in the report.
• The Dunnett-test (many to one t-test) based on a pooled variance estimate was applied, if the variables could be assumed to follow a normal distribution for the comparison of the treated groups and the control groups for each sex.
• The Steel-test (many-one rank test) was applied instead of the Dunnett-test when the data could not be assumed to follow a normal distribution.
• Fisher's exact-test was applied, if the variables could be dichotomized without loss of information.

Indices:

No indices were calculated as percentages were used.

Historical control data:

Tables summarizing the available historical control data from six studies performed at the test site (referenced 12/02, 12/03, 12/04, 13/01, 13/02 and 13/03) are given in Appendix V of the study report.
Historical control data were used in the discussion of foetal Visceral Abnormalities and Variations (incidence of the left-sided umbilical artery in group 4 marginally exceeded the upper range of the historical control data).
The number of foetal retinal folds observed in the control group was not in accordance with the occurrence reported in the historical control values where no retinal folds were observed. This could be explained by the fact that the source of the Bouin’s fixative for the present study was different from that used in studies that compiled the historical control data; this difference was considered to be a potential cause for the slight (but not clearly dose-related) increase in retinal folds noted (see Discussion of Retinal Folds observations, below).

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Description (incidence and severity):

No clinical symptoms or signs were observed at any dose level during the gestation period.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Description (incidence):

All females survived until the scheduled necropsy.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

No effects on mean absolute body weights were recorded.
The mean body weight gain was significantly lower (p<0.01) from day 9 p.c. in group 4 when compared to the controls (40 % in group 4 vs. 46 % in the controls on day 21).
The corrected body weight gain (corrected for the gravid uterus weight) was significant lower in group 4 (p<0.01) when compared to the controls (8.0 vs. 11.5 % in the controls on day 21). The effects on body weight gain and corrected body weight gain in group 4 were considered test item-related.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

No test item-related changes were observed in the food consumption during the study.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Description (incidence and severity):

No findings were observed at any dose level during macroscopic examination.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Details on results:

All females survived until the scheduled necropsy. No clinical signs were recorded in any group and the mean daily food consumption of all groups compared favourably. Although the mean absolute body weights were unaffected, a statistically significant lower mean body weight gain in group 4 (40 vs. 46 % in the controls on day 21 post coitum) and a statistically significant decreased corrected body weight gain (corrected for the gravid uterus weight) in group 4 (8.0 vs. 11.5 % in the controls on day 21) were considered to be test item-related. The reproduction data (post-implantation loss and mean number of foetuses per dam) was unaffected by treatment and no macroscopical findings were noted at any dose level.

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

not examined

Dead fetuses:

no effects observed

Changes in pregnancy duration:

not examined

Changes in number of pregnant:

not examined

Other effects:

no effects observed

Description (incidence and severity):

Placenta weights were not affected by the treatment with the test item at any dose level. Mean placenta weights calculated on a litter basis were: 0.505 g, 0.485 g, 0.490 g and 0.495 g whereas calculated on an individual basis, they were 0.503 g, 0.483 g, 0.489 g and 0.495 g, both cited in order of ascending dose level. Mean values calculated on an individual basis were significantly lower in group 2 (p<0.05) when compared to the control. In the absence of a dose-response relationship, the difference was considered to be unrelated to the treatment.

Details on maternal toxic effects:

The statistically significant decrease in the implantation sites and increase in pre-implantation loss in group 2 was not test item-related since this was a single outlying value (female no. 48) and occurred before treatment started.
The relevant reproduction data (post implantation loss and number of foetuses per dam) were not affected by treatment with the test item.

Effect levels (maternal animals)

1

Dose descriptor:

NOEL

Remarks:

(maternal toxicity)

Effect level:

300 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

2

Key result

Dose descriptor:

NOAEL

Remarks:

(maternal toxicity)

Effect level:

>= 1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks on result:

not determinable due to absence of adverse toxic effects

Maternal abnormalities

Abnormalities:

effects observed, treatment-related

Results (fetuses)

Fetal body weight changes:

no effects observed

Description (incidence and severity):

When compared with the controls, lower mean body weights of live foetuses were noted in group 4 (-6.1 % on litter basis and -8.2 % on individual basis). The difference attained statistical significance (p<0.01) and was considered to be test item-related. Both male and female foetuses in group 4 were significantly lower (all p<0.01) when compared with the controls.
The mean live foetus body weight of group 3 was similar to that of the control group.
The individual and litter mean body weight of live foetuses in group 2 was marginally lower (-2 %) than the controls; the reduction noted in mean individual foetus weights was statistically significant but unrelated to dose and therefore considered to be unrelated to the test item.

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Description (incidence and severity):

No test item-related effects on the sex ratio of the foetuses were noted in any group.
The proportion of male foetuses was 49.4, 54.7, 49.8 and 50.4 % in order of ascending dose level.

Changes in litter size and weights:

not examined

Changes in postnatal survival:

not examined

External malformations:

effects observed, non-treatment-related

Description (incidence and severity):

No test item-related findings were observed during external examination of the foetuses.
Umbilical hernia was recorded in one female foetus of group 3. A domed head, protruding tongue, and short and flexed forelimbs were recorded in one male foetus of group 4. These findings were recorded in single animals and therefore considered to be incidental.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Bone and Cartilage Abnormalities and Variations
During skeletal examination of the foetuses, findings were noted in:
15 % examined foetuses (in 67 % litters) in group 1
15 % examined foetuses (in 57 % litters) in group 2
17 % examined foetuses (in 67 % litters) in group 3
17 % examined foetuses (in 60 % litters) in group 4
A small number of bone and cartilage abnormalities were noted in treated and control groups. The incidence of the findings in the treated groups was low, were not related to dose and considered to be of no toxicological relevance.
All bone and cartilage variations noted in treated groups were considered to be unrelated to the test item. The incidence of the findings in the treated groups was low and unrelated to dose.

Ossification and Supernumerary Ribs
There were no test item-related effects on the stage of development in any dose group.
The significantly increased incidence of incomplete ossification of sternabrae 5 or non-ossification of calcanei (bilateral) were considered likely to be a secondary result of the lower mean dam body weight gain and/or foetal body weights. These structures typically show high rates of non- or incomplete ossification in control rat foetuses and therefore a relationship with the test item treatment is considered unlikely.

Additional Cartilage Variations
All additional cartilage variations noted in treated groups were considered to be unrelated to the test item. The incidence of the findings in the treated groups was low and unrelated to dose.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

During visceral examination of the foetuses, findings were noted in:
63 % examined foetuses (in 100 % litters) in group 1
62 % examined foetuses (in 100 % litters) in group 2
57 % examined foetuses (in 100 % litters) in group 3
68 % examined foetuses (in 100 % litters) in group 4
No test item-related visceral abnormalities were noted. All abnormal changes were noted at low incidence and were unrelated to dose.
The high incidence of retinal folds noted in the foetuses of groups 3 and 4 was considered to be an artefact of fixation. All other changes were noted at low incidence and were unrelated to dose.
Although the incidence of the left-sided umbilical artery in group 4 marginally exceeded the upper range of the historical control data, the finding was noted at lower incidence in group 3 than in either group 2 or the control group. Therefore, this latter difference was considered to be of no toxicological relevance.

Details on embryotoxic / teratogenic effects:

The mean placenta weights of all groups were similar. The external examination of the foetuses showed no abnormalities of toxicological relevance and sex ratios were unaffected. Foetuses of group 4 dams had lower mean body weights (-6 % on litter basis and -8 % on individual basis). This was considered to be related to the treatment with test item.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

300 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

fetal/pup body weight changes

Fetal abnormalities

Abnormalities:

no effects observed

Overall developmental toxicity

Developmental effects observed:

yes

Lowest effective dose / conc.:

1 000 mg/kg bw/day (nominal)

Treatment related:

yes

Relation to maternal toxicity:

developmental effects in the absence of maternal toxicity effects

Dose response relationship:

yes

Relevant for humans:

not specified

Any other information on results incl. tables

Table 1: Summary of Performance of Mated Females

Group Dose (mg/kg)	1 (0)	2 (100)	3 (300)	4 (1000)
Female numbers	1 - 24	25 - 48	49 - 72	73 - 96
Number of mated females	24	24	24	24
Not pregnant (A)	3	3	3	4
Number of females with live foetuses at termination*	21	21	21	20

* Only dams with at least one live foetus at caesarean section were used for the calculations of food consumption, body weight gain and corrected body weight gain data.

(A) Females no. 4, 15, 24, 35, 43, 47, 49, 56, 61, 73, 78, 83, and 87 were not pregnant.

Applicant's summary and conclusion

Conclusions:

NOEL maternal toxicity 300 mg/kg bw/day, NOAEL maternal toxicity 1000 mg/kg bw/day or higher (body weight effects)
NOEL and the NOAEL prenatal development 300 mg/kg/day (lower mean foetal weights).

Executive summary:

The oral (gavage) prenatal developmental toxicity of the test item Propylidynetrimethyl trimethacrylate (CAS 3290-92-4) to Wistar rats was investigated in a GLP-compliant dose-effect study according to the OECD TG 414 (2001) guideline.

The purpose of this study was to detect effects on the pregnant rat and development of the embryo and foetus consequent to exposure of the female to the test item from day 6 post coitum (implantation) to day 20 post coitum (the day prior to caesarean section). Four groups of 24 mated females per group were treated by gavage once daily at nominal dose levels of 0 (control group), 100, 300 and 1000 mg/kg body weight/day (named groups 1 to 4, respectively). A standard dose volume of 4 mL/kg body weight with a daily adjustment to the actual body weight was used. Control animals were dosed with the vehicle alone (corn oil). All females were sacrificed on day 21 post coitum and the foetuses were removed by caesarean section.

All females survived until the scheduled necropsy. No clinical signs were recorded in any group, and the mean daily food consumption of all groups compared favourably. Although the mean absolute body weights were unaffected, a statistically significant lower mean body weight gain of the dams in group 4 (40 vs. 46 % in the controls on day 21 post coitum) and a statistically significant decreased corrected body weight gain (corrected for the gravid uterus weight) in group 4 (8.0 vs. 11.5 % in the controls on day 21) were considered to be test item-related. The reproduction data (post-implantation loss and mean number of foetuses per dam) was unaffected by treatment and no macroscopical findings were noted at any dose level.

The mean placenta weights of all groups were similar. The external examination of the foetuses showed no abnormalities of toxicological relevance and sex ratios were unaffected. Foetuses of group 4 dams had lower mean body weights (-6 % on litter basis and -8 % on individual basis). This was considered to be related to the treatment with test item.

In conclusion based on the slightly lower mean body weight gain, the NOEL (No Observed Effect Level) for maternal toxicity was considered to be 300 mg/kg bw/day, whereas the NOAEL (No Observed Adverse Effect Level) for maternal toxicity was considered to be 1000 mg/kg bw/day or higher. For prenatal development, the NOEL (No Observed Effect Level) and the NOAEL (No Observed Adverse Effect Level) were considered to be 300 mg/kg/day, based on the lower mean foetal weights noted at 1000 mg/kg/day.