1,3-diethyl-2-thiourea

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental Starting Date (Animal Arrival): 16 February 2023
Audited Draft Report Date: December 2023
Final Report Date: April 2024

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Title:

Unnamed

Year:

2023

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:

1,3-diethyl-2-thiourea

EC Number:

203-308-5

EC Name:

1,3-diethyl-2-thiourea

Cas Number:

105-55-5

Molecular formula:

C5H12N2S

IUPAC Name:

1,3-diethyl-2-thiourea

Test material form:

solid: particulate/powder

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

Air supply: Filtered, not recirculated.
Temperature: Maintained within the range of 20-24ºC.
Relative humidity: Maintained within the range of 40-70%.
Lighting: 12 hours light : 12 hours dark.
Diet supply: SDS VRF1 Certified, Pelleted diet (ad libitum).
Water supply: Potable water from the public supply (ad libitum).

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

Treated at: Constant doses in mg/kg/day.
Volume dose: 4 mL/kg/day.
Individual dose volume: Calculated from the most recently recorded scheduled body weight.
Controls (Group 1): Vehicle at the same volume dose as treated groups.
Frequency: Once daily, at approximately the same time each day.
Sequence: Groups dosed in ascending order.
Method: Before administering the test substance, the required amount of dose formulation is drawn up into the syringe. After the dose has been drawn up the outside of the catheter is wiped clean of formulation residue with a disposable tissue and the end of the catheter will be lightly tapped onto clean tissue to remove any remaining droplets. The catheter will then be dipped into a container filled with 5% glucose solution.
Formulation: A record of the usage of formulation will be maintained based on weights. This balance may be compared with the expected usage as a check of correct administration if any discrepancy is suspected.
Formulations are stirred using a magnetic stirrer before and throughout the dosing procedure. Alternative methods may be used; these will be documented in the study records.
Storage of formulation: Refrigerated (2 to 8ºC).
Expected appearance of formulation: Orange opaque suspension.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

First Week and Last Week

Details on mating procedure:

Animals will be supplied time mated to identified males of the same strain and source. Arrival on GD 2 over four delivery dates.

Duration of treatment / exposure:

GD 6 to 20.

Frequency of treatment:

Once daily

Duration of test:

Termination on GD 21

No. of animals per sex per dose:

22 mated females/dose

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

Clinical Observations: Visually inspected at least twice daily for evidence of reaction to treatment or ill-health. Physical examination: GD 3, 5, 12, 18 and 21.
Body weight: GD 3, 6-21.
Food consumption: GD 3-6, 6-9, 9-12, 12-15, 15-18 and 18-21.
Thyroid hormone analysis: All adults surviving to scheduled termination on GD 21.
Light Microscopy: Thyroid.

Ovaries and uterine content:

For females surviving to GD 21 only, the following will be recorded:
Uterus: Gravid uterine weight (including cervix and ovaries).
The following will be recorded for all animals (including those prematurely sacrificed, where possible):
Each ovary/uterine horn, number of:
Corpora lutea.
Implantation sites.
Resorption sites (assessed as early or late).
Fetuses (live and dead).

Apparently non pregnant animals: Status confirmed by appropriate staining technique for presence of implantation sites.

Blood sampling:

All adults surviving to scheduled termination on GD 21.

Fetal examinations:

Fetal Examination
All live fetuses: Fetuses and placentae dissected from the uterus and weighed individually. Fetuses sexed. Ano-genital distance recorded. External examination with particular attention paid to external genital organs of male fetuses. Individual identification within litter.
50% in each litter: Sex confirmed internally. Examined for visceral abnormalities by fresh microdissection (Modified Staples technique) and subsequently fixed in Bouins solution.
50% in each litter: Sex confirmed internally, eviscerated and fixed in Industrial Methylated Spirit.

Fetal processing
Bouin’s fixed fetuses: Head removed post-fixation and heads processed by Wilsons free-hand serial sectioning. Torsos retained in Bouins solution.
IMS fixed fetuses: Processed and stained with Alizarin Red and Alcian Blue.

Detailed Fetal Examination
Bouin’s fixed heads: Serial sections examined for visceral abnormalities.
Fetuses, stained with Alizarin Red and Alcian Blue: Skeletal development, cartilage and abnormalities assessed.

Statistics:

Included

Historical control data:

Recent HCD will be provided by the CRO.

Results and discussion

Results: maternal animals

Effect levels (maternal animals)

Remarks on result:

not determinable

Remarks:

Conclusion will be reached once the study has been completed.

Maternal abnormalities

Abnormalities:

not specified

Results (fetuses)

Effect levels (fetuses)

Remarks on result:

not determinable

Remarks:

Conclusion will be reached once the study has been completed.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Assessment of the influence of 1,3-diethyl-2-thiourea on embryo-fetal survival and development when administered during the organogenesis and fetal growth phases of pregnancy in the Han Wistar rats.