N-vinylformamide

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

N-vinylformamide

EC Number:

236-102-9

EC Name:

N-vinylformamide

Cas Number:

13162-05-5

Molecular formula:

C3H5NO

IUPAC Name:

N-vinylformamide

Details on test material:

- Name of test substance: N-Vinylformamide rein
- CAS No.: 13162-05-5
- Homogeneity: Given
- Physical state/Appearance: Liquid / yellowish, clear

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH
- Age at study initiation: about 10-12 weeks
- Weight at study initiation: 154.5 – 194.8 g
- Housing: individually in Polycarbonate cages type III
- Diet: ground Kliba maintenance diet mouse/rat “GLP”, meal, supplied by Provimi Kliba SA, Kaiseraugst, Switzerland ad libitum
- Water (e.g. ad libitum): potable tap water ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 30-70%
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The aqueous test substance preparations were prepared at the beginning of the administration period and thereafter at intervals, which took into account the period of established stability. The preparations were kept at room temperature. For the test substance preparations the specific amount of test substance was weighed, topped up with drinking water in a graduated flask and intensely mixed by shaking until it was dissolved.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The analytical investigations of the test substance preparations were carried out at the Analytical Chemistry Laboratory of Experimental Toxicology and Ecology of BASF SE, Ludwigshafen, Germany. Analytical verifications of the stability of the test substance in drinking water over a period of 7 days at room temperature were conducted prior to the start of the study. Samples of the test substance preparations were sent to the analytical laboratory at the beginning of administration for verification of the concentrations. Given that the test substance was completely miscible with drinking water, solutions were considered to be homogenous without further analysis.
- Technique: HPLC
- System: Agilent 1200 with autosampler, DAD, Dionex Chromeleon – Software (Dionex), or equivalent system
- Column: Length: 250 mm; Inner diameter: 4.6 mm
- Stationary Phase: Primesep 200, 5 µm, Sielc or equivalent
- Mobile Phase A: 950 mL acetonitrile are mixed with 50 mL water and 1 mL formic acid
- Mobile Phase B: 950 mL water are mixed with 50 mL acetonitrile and 1 mL formic acid
- Isocratic: Mobile Phase A - 0%; Mobile Phase B - 100%
- Injection volume: 5 µL
- Flow rate: 1.0 mL/min
- Detection (wavelength): 225 nm
- Reference wavelength: 360 nm (the reference wavelength has to be used when this is technically feasible by the detector)
- Column temperature: Ambient
- Run time: Approx. 7 min

Details on mating procedure:

- Impregnation procedure: purchased timed pregnant
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as GD 0

Duration of treatment / exposure:

from implantation to one day prior to the expected day of parturition (GD 6-19)

Frequency of treatment:

daily

Duration of test:

20 days

Doses / concentrations

Remarks:

Doses / Concentrations:
8, 25, 80 mg/kg bw/d
Basis:
nominal conc.

No. of animals per sex per dose:

25 time-mated female Wistar rats per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose selection was based on the results of a maternal toxicity study in female Wistar rats (range-finding)
- Other: The animals were paired by the breeder (“time-mated”); the day of evidence of mating (= detection of vaginal plug/sperm) was referred to as GD 0. The animals arrived on the same day (GD 0) at the experimental laboratory. The following day was designated as “GD 1”. The animals were acclimated to the laboratory conditions between start of the study (beginning of the experimental phase) and first administration (GD 6). The body weight of the pregnant animals on day 0 varied between 154.5 – 194.8 g. The test substance preparations were administered to the animals once a day orally by gavage, from implantation to one day prior to the expected day of parturition (GD 6 to GD 19), always at approximately the same time in the morning. The animals of the control group were treated with the vehicle (drinking water) in the same way. The volume administered each day was 10 mL/kg body weight. The calculation of the administration volume was based on the most recent individual body weight. On GD 20, all surviving dams were sacrificed and examined . The fetuses were removed from the uterus and investigated.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: A check was made twice a day on working days or once a day on Saturdays, Sundays or on public holidays (GD 0-20).

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: A cage-side examination was conducted at least once daily for any signs of morbidity, pertinent behavioral changes and signs of overt toxicity. If such signs occurred, the animals were examined several times daily (GD 0-20).

BODY WEIGHT: Yes
- Time schedule for examinations: All animals were weighed on GD 0, 1, 3, 6, 8, 10, 13, 15, 17, 19 and 20. The body weight change of the animals was calculated based on the obtained results. Furthermore, the corrected body weight gain was calculated after terminal sacrifice (terminal body weight on GD 20 minus weight of the unopened uterus minus body weight on GD 6).

FOOD CONSUMPTION: Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- The consumption of food was recorded for the intervals GD 0-1, 1-3, 3-6, 6-8, 8-10, 10-13, 13-15, 15-17, 17-19 and 19-20.

WATER CONSUMPTION: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #20
- Organs examined: On GD 20 all surviving dams were sacrificed by decapitation under isoflurane anesthesia in a randomized sequence. The exsanguinated animals were necropsied and assessed by gross pathology, special attention being given to the reproductive organs. Liver weights were determined in all animals sacrificed on schedule. The carcass weights were used to calculate the relative organ weights. All gross lesions and liver were fixed in 4% neutral-buffered formaldehyde solution or in modified Davidson’s solution. Fixation was followed by histotechnical processing, examination by light microscopy and assessment of findings of the liver (Hematoxylin and Eosin (H&E) stain) of all animals per test group. After completion of the histopathological assessment by the study pathologist an internal peer review was performed by another pathologist from BASF SE, Ludwigshafen, including liver of all animals. Results presented in this report reflect the consensus opinion of the study pathologist and the peer review pathologist.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Dead fetuses (hypoxemic fetuses which did not breathe spontaneously after the uterus had been opened)

Fetal examinations:

All fetal analyses were conducted by technicians unaware of the treatment group, in order to minimize bias.
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: all per litter

Statistics:

For food consumption, body weight, body weight change, corrected body weight gain (net maternal body weight change), carcass weight, weight of unopened uterus, number of corpora lutea, number of implantations, number of resorptions, number of live fetuses, proportions of preimplantation loss, proportions of postimplantation loss, proportions of resorptions, proportion of live fetuses in each litter, litter mean fetal body weight and litter mean placental weight a simultaneous comparison of all dose groups with the control group using the DUNNETT-test (two-sided) for the hypothesis of equal means was performed.
Female mortality, females pregnant at terminal sacrifice and number of litters with fetal findings were evaluated by pairwise comparison of each dose group with the control group using FISHER'S EXACT test (one-sided) for the hypothesis of equal proportions.
Proportions of fetuses with malformations, variations and/or unclassified observations in each litter were evaluated by pairwise comparison of each dose group with the control group using the WILCOXON-test (one-sided) for the hypothesis of equal medians.
Weight parameters during pathology were evaluated by a non-parametric one-way analysis using KRUSKAL-WALLIS test (two-sided). If the resulting p-value was equal or less than 0.05, a pairwise comparison of each dose group with the control group was performed using WILCOXON-test (two-sided) for the equal medians.

Indices:

The following Indices have been determined:
Conception rate (in %), preimplantation loss (in %) and postimplantation loss (in %).

Historical control data:

Historical control data was used to compare findings regarding reproduction data of the dams and external malformations and soft tissue malformations as well as soft tissue variations of the fetuses. Furthermore skeletal malformations as well as variations in the fetuses were compared.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Details on maternal toxic effects:
Only pregnant dams were used for the calculations of mean maternal food consumption, body weight and body weight change. Only pregnant dams with scheduled sacrifice (GD 20) were used for the calculation of mean gravid uterine weights, corrected (net) body weight gain and summary of reproduction data.
Therefore, one non-pregnant female of test group 2 (25 mg/kg bw/d) was excluded from the above-mentioned calculations.

MORTALITY
There were no test substance-related or spontaneous mortalities in any females of all test groups (0, 8, 25 or 80 mg/kg bw/d).

DETAILED CLINICAL OBSERVATIONS
No clinical signs or changes of general behavior, which may be attributed to the test substance, were detected in any female at dose levels of 8, 25 or 80 mg/kg bw/d during the entire study period.

BODY WEIGHT
The mean body weight (BW) and body weight gain (BWC) of the high-dose rats (80 mg/kg bw/d) were statistically significantly reduced during several days of the treatment period (BW on GD 8-20, BWC on GD 6-8 and GD 19-20), which was likely to be a subsequent effect of reduced food consumption. Furthermore, mean BWC was statistically significantly decreased on GD 13-15. If calculated for the entire treatment period (GD 6-19) or the whole study period (GD 0-20) the mean body weight gain was 28% or 21% below the concurrent control values (attaining statistical significance). This effect was considered as test substance-related.
The BW and the average BWC of the low- and mid-dose dams (8 and 25 mg/kg bw/d) were generally comparable to the concurrent control group throughout the entire study period. This includes the statistically significantly increased BWC value in test group 1 on GD 17-18 and the decreased BWC value in test group 2 on GD 6-8.
The corrected body weight gain (terminal body weight on GD 20 minus weight of the unopened uterus minus body weight on GD 6) was distinctly and statistically significantly lower in test group 3 (80 mg/kg bw/d - about 56% below the concurrent control value). Furthermore, the carcass weight of the high-dose dams was also statistically significantly lower in comparison to the control group (about 7% below controls). These effects are assessed as test substance-related signs of maternal toxicity.
The corrected body weight gain of test groups 1 and 2 (8 and 25 mg/kg bw/d) revealed no difference of biological relevance to the corresponding control group. Moreover, mean carcass weights remained also unaffected by the treatment.

FOOD CONSUMPTION
The mean food consumption of the dams in test group 3 (80 mg/kg bw/d) was statistically significantly reduced from GD 6-13, but recovered afterwards. Nevertheless, during the treatment period (GD 6-19) the high-dose dams consumed 20% less food in comparison to the concurrent control group. The reduced food consumption was considered as test substance-related. The mean food consumption of the dams in test groups 1 and 2 (8 and 25 mg/kg bw/d) was generally comparable to the concurrent control group throughout the whole study period.

POST-MORTEM EXAMINATIONS
UTERUS WEIGHT:
The mean gravid uterus weights of the animals of test group 1-3 (8, 25 and 80 mg/kg bw/d) were not influenced by the test substance. The differences between these groups and the control group revealed no dose-dependency and were assessed to be without biological relevance.

REPRODUCTION DATA:
The conception rate was 96% in the mid-dose group (25 mg/kg bw/d) and 100% in the control, low- and high-dose groups (0, 8 and 80 mg/kg bw/d). With these rates, a sufficient number of pregnant females were available for the purpose of the study.
There were no test substance-related and/or biologically relevant differences between test groups 0, 1, 2 and 3 (0, 8, 25 and 80 mg/kg bw/d) in conception rate, in the mean number of corpora lutea and implantation sites or in the values calculated for the pre- and the postimplantation losses, the number of resorptions and viable fetuses. All observed differences are considered to reflect the normal range of fluctuations for animals of this strain and age.

NECROPSY FINDINGS:
- Gross lesions: All findings occurred individually. They were considered to be incidental or spontaneous in origin and without any relation to treatment.
- Absolute organ weights: When compared to control group 0 (set to 100%), the mean absolute terminal body weight of test group 3 animals was significantly decreased and the absolute weight of the liver of test group 2 females was significantly increased (see table below).
- Relative organ weights: When compared to control group 0 (set to 100%), the mean absolute liver weights were significantly increased in test groups 2 and 3 (see table below).
Both the decrease in terminal body weight of test group 3 and the increase of absolute and/or relative liver weight in test group 2 and 3 was regarded to be treatment-related.
- Histopathology: Treatment-related single cell necrosis was observed in the liver of females of test groups 2 and 3 (see table below). All other findings occurred either individually or were biologically equally distributed over control and treatment groups. They were considered to be incidental or spontaneous in origin and without any relation to treatment.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

8 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Details on embryotoxic / teratogenic effects:
SEX DISTRIBUTION
The sex distribution of the fetuses in test groups 1-3 (8, 25 and 80 mg/kg bw/d) was comparable to the control fetuses.

WEIGHT OF PLACENTAE AND FETUSES
The mean placental weights of the low-, mid- and high-dose groups (8, 25 and 80 mg/kg bw/d) were comparable to the corresponding control group.
The mean fetal weights of test groups 1, 2 and 3 (8, 25 and 80 mg/kg bw/d) were not influenced by the test substance and did not show any biologically relevant differences in comparison to the control group.

FETAL EXTERNAL EXAMINATION
Three external malformations were recorded, each, for one fetus of test group 2 (25 mg/kg bw/d) and one fetus of test group 3 (80 mg/kg bw/d). For the affected fetuses, these external findings were associated with visceral malformations. The total incidence of external malformations in treated animals did not differ significantly from the control group and was comparable to the historical control data.
No external variations or unclassified observations were recorded.

FETAL SOFT TISSUE EXAMINATIONS
Soft tissue malformations occurred in one fetus, each, of the low-dose and mid-dose group (8 and 25 mg/kg bw/d) and in two fetuses of the high-dose group (80 mg/kg bw/d). Male mid-dose fetus No. 71-08 had multiple visceral malformations, i.e. misshapen liver (swollen, fused or absent liver lobes, discolored liver), enlarged spleen, small kidneys, small thymus, long drawn-out heart, high-arched aortic arch and short innominate. These visceral findings were associated with external malformations. The total incidence of soft tissue malformations in treated animals did not differ significantly from the control group and was comparable to the historical control data.
Three soft tissue variations, i.e. short innominate, dilated renal pelvis and dilated ureter, were detected in test groups 0-2 (0, 8 and 25 mg/kg bw/d). The incidences of these variations were neither statistically significantly different from control nor dose-dependent, and therefore not considered biologically relevant. All of them can be found in the historical control data at comparable incidences.
No soft tissue unclassified observations were recorded.

FETAL SKELETAL EXAMINATION
Some skeletal malformations were detected in single fetuses of all test groups (0, 8, 25 or 80 mg/kg bw/d). The incidences of these malformations were neither statistically significantly different from control nor dose-dependent, and therefore not considered biologically relevant.
For all test groups, skeletal variations of different bone structures were observed, with or without effects on corresponding cartilages. The observed skeletal variations were related to several parts of fetal skeletons and appeared without a relation to dosing. The overall incidences of skeletal variations were comparable to the historical control data. For a better overview, all skeletal variations with statistically significant differences between the control and any treated group were compiled in the table below. All incidences were expressed on a fetus per litter basis and any statistically significant differences, which were outside historical control ranges were marked in bold and italics types. As can be seen from the table below, the rate of incomplete ossification of supraoccipital (unchanged cartilage) was statistically significantly increased in test group 3 (80 mg/kg bw/d) and slightly outside the historical control range. This minor change may represent a slight delay of ossification which did not affect morphology, as the underlying cartilage model was completely intact. In the historical background data, increased incidences of such incomplete or non-ossifications of skeletal elements are routinely quantified and are among the most frequently noted skeletal variants in control populations of this Crl:WI(Han) rat strain. This indicates that these findings reflect species-specific anatomic variation at the time around birth without any detrimental effects on further development.
Additionally, some isolated cartilage findings without impact on the respective bony structures, which were designated as unclassified cartilage observations, occurred in all test groups. The observed unclassified cartilage findings were related to the skull, the ribs and the sternum and did not show any relation to dosing.

OVERALL ASSESSMENT
There were noted external, soft tissue and skeletal malformations in one control, two low-dose, two mid-dose and three high-dose fetuses.
Two fetuses were multiple-malformed. Male mid-dose fetus No. 71-08 (25 mg/kg bw/d) had anasarca and anal atresia, combined with multiple visceral malformations (i.e. misshapen liver [swollen, fused or absent liver lobes, discolored liver], enlarged spleen, small kidneys, small thymus, long drawn-out heart, high-arched aortic arch and short innominate). The findings in high-dose female fetus No. 92-03 (80 mg/kg bw/d) consisted of gastroschisis, situs inversus and a small spleen. No ontogenetic pattern is recognizable for the individual malformations nor was there any cluster of any of these individual malformations seen in the other offspring of the test groups. Most of them are present in the historical control data of the rat strain. Thus, a relationship to the treatment is not assumed.
Further malformations, i.e. hydronephrosis, fused liver lobes, misshapen basisphenoid, misshapen thoracic vertebra and malpositioned and bipartite sternebra were not related to dose and most of them can be found in the historical control data. An association of these findings to the treatment is also not assumed.
The total incidences of malformations are summarized in the table below.
External variations did not occur in any of the fetuses of the study. A spontaneous origin is assumed for three soft tissue variations which were observed in fetuses of test groups 0-2. A broad range of skeletal variations occurred in all test groups including the control. The majority of the skeletal variations are equally distributed among the different test groups including controls, if normal biological variation is taken into account, and can be found in the historical control data at similar frequencies.
One single variation - incomplete ossification of supraoccipital (unchanged cartilage) - was statistically significantly increased in test group 3 (80 mg/kg bw/d) and slightly outside the historical control range. This minor change may represent a slight delay of ossification which did not affect morphology, as the underlying cartilage model was completely intact. In the historical background data, increased incidences of such incomplete or non-ossifications of skeletal elements are routinely quantified and are among the most frequently noted skeletal variants in control populations of this Crl:WI(Han) rat strain. This indicates that these finding reflect species-specific anatomic variation at the time around birth without any detrimental effects on further development. Notably, the marginal increase of these changes did not affect the overall rate of variations, as can be seen from the table below.
Concerning the other statistically significant findings, no dose dependency was observed and/or all values were clearly inside the historical control range, thus, an association to the test substance and a toxicological relevance is not assumed.
No unclassified external and unclassified soft tissue observations were recorded for any of the fetuses in this study.
A spontaneous origin is assumed for the unclassified skeletal cartilage observations which were observed in several fetuses of test groups 0, 1, 2 and 3 (0, 8, 25 and 80 mg/kg bw/d). The distribution and type of these findings do not suggest any relation to treatment.
Finally, fetal examinations revealed that there is no effect of the compound on the respective morphological structures up to a dose of 80 mg/kg bw/d.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

80 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

EXAMINATION OF THE DAMS

Absolute organ weights:

Absolute weights	Females
Test group (mg/kg bw/d)	1 (8)	2 (25)	3 (80)
Terminal body weight	99%	100%	93%**
Liver	100%	107%**	103%

*: p<=0.05, **: p<=0.01

 

Relative organ weights:

Relative weights	Females
Test group (mg/kg bw/d)	1 (8)	2 (25)	3 (80)
Liver	101%	107%**	110%**

*: p<=0.05, **: p<=0.01

 

Histopathology:

	Female animals
Test group (mg/kg bw/d)	0 (0)	1 (8)	2 (25)	3 (80)
No.of animals	25	25	25	25
Necrosis, single cell			12	25
Grade 1			10	2
Grade 2			2	9
Grade 3				14

  

 

EXAMINATION OF THE FETUSES

Occurrence of statistically significantly increased fetal skeletal variations (expressed as mean percentage of affected fetuses/litter):

Finding	Test group 0 0 mg/kg bw/d	Test group 1 8 mg/kg bw/d	Test group 2 25 mg/kg bw/d	Test group 3 80 mg/kg bw/d	HCD Mean % (range)
Incomplete ossification of supraoccipital; unchanged cartilage	46.6	45.4	53.4	67.4**	43.3 (10.3–64.3)
Dumbbell ossification of thoracic centrum; unchanged cartilage	3.2	5.6	5.8	7.1*	5.6 (0.0–14.5)
Misshapen sternebra; unchanged cartilage	32.9	49.9*	42.2	42.9	51.3 (29.5–76.9)

mg/kg bw/d = milligram per kilogram body weight per day; HCD = Historical control data; % = per cent

* = p ≤ 0.05 (Wilcoxon-test [one-sided]), ** = p ≤ 0.01 (Wilcoxon-test [one-sided])

 

Assessment of all fetal external, soft tissue and skeletal observations

Total fetal malformations:

		Test group 0 0 mg/kg bw/d	Test group 1 8 mg/kg bw/d	Test group 2 25 mg/kg bw/d	Test group 3 80 mg/kg bw/d
Litter Fetuses	N N	25 257	25 235	24 239	25 235
Fetal incidence	N (%)	1 (0.4)	2 (0.9)	2 (0.8)	3 (1.3)
Litter incidence	N (%)	1 (4.0)	2 (8.0)	2 (8.3)	3 (12)
Affected fetuses/litter	Mean %	0.4	0.9	0.9	1.3

mg/kg bw/d = milligram per kilogram body weight per day; N = number; % = per cent

 

Total fetal variations:

		Test group 0 0 mg/kg bw/d	Test group 1 8 mg/kg bw/d	Test group 2 25 mg/kg bw/d	Test group 3 80 mg/kg bw/d
Litter Fetuses	N N	25 257	25 235	24 239	25 235
Fetal incidence	N (%)	137 (53)	124 (53)	125 (52)	119 (51)
Litter incidence	N (%)	25 (100)	25 (100)	24 (100)	25 (100)
Affected fetuses/litter	Mean %	53.6	53.4	52.5	50.2

mg/kg bw/d = milligram per kilogram body weight per day; N = number; % = per cent

Applicant's summary and conclusion

Conclusions:

Under the conditions of this prenatal developmental toxicity study, the oral administration of N-Vinylformamide rein to pregnant Wistar rats from implantation to one day prior to the expected day of parturition (GD 6-19) at a dose of 80 mg/kg bw/d caused evidence of maternal toxicity, such as temporarily reduced food consumption, decreased body weight development as well as single cell necrosis in the liver of the animals. Whereas the impairment of the clinical parameters was only seen in the high-dose group, the adverse liver effects were still present (in a lower incidence) at a dose of 25 mg/kg bw/d.
In conclusion, the no observed adverse effect level (NOAEL) for maternal toxicity is 8 mg/kg bw/d.
The no observed adverse effect level (NOAEL) for prenatal developmental toxicity is 80 mg/kg bw/d. The test item is not teratogenic in rats.

Executive summary:

In a prenatal developmental toxicity study, the test substance N-Vinylformamide rein was administered to pregnant Wistar rats daily by gavage from implantation to one day prior to the expected day of parturition (GD 6-19) to evaluate its potential maternal and prenatal developmental toxicity.

Analyses confirmed the correctness of the prepared concentrations and the stability of the test substance in the vehicle.

Generally, clinical observations revealed no toxicologically relevant difference between the animals receiving 8 or 25 mg/kg bw/d N-Vinylformamide rein and controls.

The mean food consumption of the high-dose dams (80 mg/kg bw/d) was decreased statistically significantly on GD 6-13. Afterwards it recovered, but calculating the food consumption during the whole administration period (GD 6-19) it was about 20% lower than in the control animals. The high-dose of the test substance consistently affected the gross and corrected (net) body weight gain of the dams in test group 3. These dams gained overall about 28% (gross) or 56% (net) less weight than the concurrent control during the treatment period (GD 6-19). The carcass weight was about 7% below the concurrent control group. These effects were regarded to be treatment-related and adverse.

No differences of toxicological relevance between the control and the test substance-treated groups (8, 25 or 80 mg/kg bw/d) were determined for any reproductive parameters, such as conception rate, mean number of corpora lutea, mean number of implantations, as well as pre- and the postimplantation loss. Similarly, no influences of the test substance on fetal weight and sex distribution of the fetuses were noted at any dose level.

Regarding pathology, target organ was the liver. An increase in relative (test group 2 and 3) and absolute (test group 2) weight was observed in the liver without a histopathological correlate. The weight increase was assessed nevertheless as treatment-related but not adverse. Single cell necrosis of hepatocytes was noted in all high-dose and many mid-dose females, which was regarded as adverse.

All other findings occurred either individually or were biologically equally distributed over control and treatment groups. They were considered as incidental or spontaneous in origin and without any relation to treatment.

Fetal examinations revealed no effect of the compound on the respective morphological structures up to the highest dose tested (80 mg/kg bw/d). The increased incidence of one single skeletal element (incomplete ossifications of supraoccipital) in the high-dose group was associated with the maternal toxicity. It represents a temporary delay in development, which has no permanent effect on morphology and function of the affected structures. Thus, the test substance is not teratogenic in rats.

In conclusion, the NOAEL for maternal toxicity is 8 mg/kg bw/d. The NOAEL for prenatal developmental toxicity is 80 mg/kg bw/d.