Urea, reaction products with formaldehyde and glyoxal

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08.04.- 05.05.1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Reference 2

Reference Type:

secondary source

Title:

Unnamed

Year:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Details on test material:

- CAS number (as cited in study report): 1854-26-8
- Physical state: liquid
- Analytical purity: 64.1%
- Impurities (identity and concentrations):
- Composition of test material, percentage of components:
- Isomers composition:
- Purity test date: 24.02.1997
- Lot/batch No.: 494034
- Expiration date of the lot/batch: Feb 1997
- Storage condition of test material: appox. 4°C

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hoechst AG, Kastengrund, SPF breeding colony
- Age at study initiation: approximately 8 - 10 weeks
- Diet (e.g. ad libitum): Ssniff R-Z (V1324), ad libitum
- Water (e.g. ad libitum): tap water in plastic bottles
- Acclimation period: at least five days under study conditions


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.5-22.0
- Humidity (%): 35-62
- Air changes (per hr): 16-20
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Each concentration was prepared freshly each day from a separate weighed quantity of the test compound. Formulations were stirred continuously in the animal room during dosing. Homogeneity and stability of the test compound in the vehicle were assessed prior to the start of the study.

Analytical verification of doses or concentrations:

yes

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: overnight
- Proof of pregnancy: sperm in vaginal smear referred to as day 1 of pregnancy

Duration of treatment / exposure:

day 7-16 of pregnancy

Frequency of treatment:

daily

Duration of test:

21 days

Doses / concentrations

Remarks:

Doses / Concentrations:
250; 500; 1000 mg/(kg*d) [64.1 % test substance in water: 160, 320, and 640 mg/(kg*d)]
Basis:

No. of animals per sex per dose:

23

Control animals:

yes

Details on study design:

- Dose selection rationale: Based on the available toxicological data of the test compound, the dose levels of 0, 250, 500 and 1000 mg/kg body weight per day were selected for the present study. Testing of dose levels > 1000 mg/kg body weight is not necessary with regard to the Guidelines mentioned below (Limit Test).

Examinations

Maternal examinations:

All animals were examined before the start of the study and were shown to be in good general health condition. The behaviour and general health condition of the animals were observed several times daily (on weekends and public holidays once daily) .
Body weights were determined on days 1, 4, 7, 10, 14, 17, 19 and 21 of pregnancy, and food consumption was recorded between days 1-4, 4-7, 7-10, 10-14, 14-17, 17-19 and 19-21 of pregnancy.

Ovaries and uterine content:

The animals were killed on day 21 of pregnancy and the foetuses removed by Caesarean section . All animals were examined externally and internally (thoracic and abdominal contents) for macroscopically visible changes, with emphasis on the uterus. Gravid uterus weight was determined. The live and dead foetuses in the uterus as well as the conceptuses undergoing resorption and corpora lutea were counted and examined macroscopically. The implantation sites in the uterus were counted after staining with ammonium sulphide.

Fetal examinations:

The foetuses, the placentae and conceptuses undergoing resorption were removed from the uterus, weighed or measured and examined for gross external abnormalities. Crown-rump length was recorded. Then the foetuses were killed by C02 asphyxia.
Approximately 50% of the foetuses of each litter and dead foetuses were fixed in alcohol, necropsied, sexed and checked for anomalies of the internal organs. The carcasses were placed in a solution of potassium hydroxide for clearing and stained with alizarin red S. The skeletons were examined and checked for stage of development and abnormalities with the aid of a stereo-microscope. The remaining foetuses were transferred in Bouin's solution, examined for organ anomalies referring to Wilson's slicing technique (Wilson, 1965) and sexed.

Statistics:

The t-tests and the test statistics of Wilks (Hartung & Elpelt, 1984) are based on common variance estimations for all study groups. For the Wilcoxon test (Hollander & Wolfe, 1973) the exact distributon (Streitberg & R6hmel, 1987) of the meaned ranks was calculated.
In the case of the daily food consumption of the dams, the mean consumption per 100 g body weight was always calculated between two successive measurement times and evaluated by the rank sum test after Wilcoxon. In examining the body weights of the dams, the change in weight was determined in comparison to the initial weight. The univariate evaluation was carded out using t-tests.
The caesarean section data of the foetuses were used to calculate litter mean values. Multivariate evaluation was carried out using the test statistics of VVilks. In the univariate analysis, tests were used.
The number of corpora lutea, implantation sites and live foetuses, and quotas of dead embryonic primordia undergoing resorption in the animals were likewise analysed using one-sided Wilcoxon tests.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
There were no deaths during the study. No clinical signs were observed in any of the animals.
Body weight gain and food consumption were not affected by the administration of the test compound.
No compound-related effects were observed at necropsy of the animals. Dilation of the kidney pelvis was observed more frequently in the high dose group, but this finding occurs spontaneously in the rat strain used and was therefore held for not relevant.
Gravid uterus weights were comparable in all groups.
One female from the low dose group, three females from the intermediate dose group and two females from the high dose group did no tbecome pregnant.
Statistical evaluation did not reveal an increase in the incidence of the numbers of early and late conceptuses undergoing resorption and dead foetuses. Most of the resorptions were early conceptuses undergoing resorption.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

640 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
One female of the intermediate dose group had one dead foetus. There was nodose-dependency and statistical evaluation did not reveal differences between the groups.
Crown-rump lengths, litter size, number of live foetuses, foetal and placental weights remained unaffected by the administration of the test compound. Sex ratio of the foetuses was not altered by the administration of the test compound.
External, skeletal and visceral examination
Maior defects:
One markedly stunted foetus occurred in the low dose group. Bilateral dysplasia and partial aplasia of the fibula were observed in one foetus from the intermediate dose group, which also exhibited shortened femur and shortened and bent tibia. Another foetus from this dose group was edematous and showed complete fusion of lung lobes. As there was no dose dependency, a compound-related effect is unlikely.
Minor defects:
The foetuses scheduled for skeletal examination showed blood in the abdominal cavity (1/133, 0/137, 0/117, 0/131) and distension of the kidney pelvis (1/133, 1/137, 6/117, 4/131) at autopsy, the latter finding being statistically significant in the intermediate dose group. All incidences were within the historical range of the rat strain used, and there was no dose-dependency. Therefore, these findings are considered not to be treatment-related.
Minor skeletal defects consisted of splitting of bone on,interparietal bone (0/133, 0/137, 0/117, 1/131), fragmented thoracic vertebral centres (3/133, 0/137, 1/117, 0/131), fused or longitudinally displaced stemebrae (6/133, 1/137, 0/117, 0/131), wavy and/or thickened ribs (19/133, 18/137, 6/117, 171131) and costad bent scapulae (1/133, 4/137, 0/117, 0/131). In these cases, statistical evaluation did not reveal differences between the groups,and - except bent scapulae in the low dose group, which showed no dose-dependency - the values were within the historical range of the rat strain used. Therefore, a compound-related effect is not evident.
Examination of body cross-sections revealed a statistically significantly increased incidence of distended kidney pelvis in the intermediate dose group based on absolute numbers (0/122, 3/123, 4/106, 4/120) and in the intermediate and high dose group based on the number of affected litters (0/23, 3/22, 4/20, 4/21). The incidence was within the historical range of the rat strain used, and there was no dose-dependency. Therefore, a compound-related effect is not evident. Blood in the thoracic cavity was observed in one control foetus and two foetuses from the-high dose group. The latter incidence was above the historical range of the rat strain used.
However, only two foetuses were affected, and statistical evaluabon did not reveal significant differences. Therefore, a compound-related effect is not evident. Other minor defects observed at body cross-section consisted of blood in the abdominal cavity (3/122, 4/123, 1/106, 4/120), haematoma in the liver (0/122, 0/123, 1/106, 1/120), blood in the vicinity of the kidney (0/122, 0/123, 1/106, 0/120) and distended ureter (1/122, 2/123, 2/106, 0/120). In all cases, there was no dose-dependency or the values were within the historical ra nge of the rat strain used. Furthermore, statistical evaluation did not reveal differences between the groups. Therefore, these findings are considered not to be treatment-related.
Variations:
Statistical evaluation revealed an increased ificidence of an extra rib at the 7th cervical vertebra (0/133, 5/137, 2/117, 2/131) in the low dose group . This incidence was above the historical range of the rat strain used . However, there was no dose-dependency, and the incidences of the higher dose groups were within the historical range of the rat strain used . Therefore, a compound-related effect is unlikely. One foetus of the intermediate dose group showed anlage of 7 stemebrae, and an extra rib at the 1st lumbar vertebra was observed in all groups (32/133, 24/137, 19/117, 31/131) . In these cases, statistical evaluation did not reveal differences between the groups, and the incidences were within the historical range of the rat
strain used. Therefore, a compound-related effect can be ruled out.
Retardations:
Stabstical evaluation revealed increased incidences of non-ossified metacarpale 5 based on the number of affected litters (2/23, 6/22, 7/20, 5/21). Absolute incidences (4/133, 8/137,7/117, 10/131) were not statistically significant compared to the control group. All values were within the historical range of the rat strain use . Therefore, a compound-related effect is not evident. Further retardations consisted of slight- or non-ossification of individual skull bones (69/133, 58/137, 46/117, 69/131), not visible incisors (0/133, 2/137, 0/117, 0/131), weakly ossified cervical vertebral arch (1/133, 0/137, 0/117, 0/131), weakly ossified lumbar vertebral arch (2/133, 0/137, 0/117, 0/131), non ossified sacral vertebral arch or centres (0/133, 2/137, 1/117, 0/131), ossificatibn of less than two caudal vertebral centres (35/133, 42/137, 25/117, 36/131), non or weakly ossified sternebrae (27/133, 14/137, 11/117, 17/131), weakly ossified ribs (1/133, 0/1-37, 1/117, 0/131), weakly or non ossified metacarpale 2 and/or 4 (0/133, 3/137, 0/117, 1/131), non ossified phalanx III of the 1st to 5th toe of th6 forepaw (0/133, 2/137, 0/117, 0/131), non or weakly ossified ischium/pubis (0/133, 1/137, 0/117, 2/131), non ossified metatarsale 2, 3 and 4 (0/133, 1/137, 0/117, 0/131), non ossified metatarsale 5 (0/133, 2/137,
1/117, 0/131) and non ossified phalanx III of the 1st to 5th toe of the hindpaw (5/133, 4/137, 3/117, 7/131). In all these cases, statistical evaluation did not reveal differences between the groups. A compound-related effect is not evident.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

640 mg/kg bw/day

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Report available only without appendices.