1,3-diphenyl-2-thiourea

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:

comparable to guideline study

Data source

Reference

Reference Type:

publication

Title:

Difference in the developmental toxicity of ethylenethiourea and three N,N'-substituted thiourea derivatives in rats.

Author:

Saillenfait A.M., Sabate J.P., Langonne I. and De Ceaurriz J.

Year:

1991

Bibliographic source:

Fundam. Appl. Toxicol., 1991; 17: 399-408.

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,3-diphenyl-2-thiourea

EC Number:

203-004-2

EC Name:

1,3-diphenyl-2-thiourea

Cas Number:

102-08-9

Molecular formula:

C13H12N2S

IUPAC Name:

1,3-diphenyl-2-thiourea

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material (as cited in study report): DPT, DPTU
- Source: Aldrich Chemical Company (Milwaukee, WI).
- Batch number: no data
- Purity: > 98 %

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: From IFFA CREDO Breeding Laboratories (St Germain sur l'arbresle, France)
- Age at study initiation: no data
- Weight at study initiation: males = 350 g ; females = 200-220 g
- Fasting period before study: no data
- Housing: Bred females were individually housed in clear polycarbonate cages with hardwood shavings as bedding.
- Diet (e.g. ad libitum): UAR Alimentation Villemoisson, ad libitum
- Water (e.g. ad libitum): filtered tap water, ad libitum
- Acclimation period: 1 or 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- °C
- Humidity (%): 55 +/- 5%
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): a light cycle from 7AM to 7 PM

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

- Total volume applied: 5 ml/kg body wt
- Control group: received the vehicle alone (20 animals)

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1M / 3 F
- Length of cohabitation: overnight
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

from gestational days 6 to 20

Frequency of treatment:

daily, at approximately the same time each time

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

Doses / concentrations 4

Dose / conc.:

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

No. of animals per sex per dose:

20 or 21 females

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

- Maternal observations: daily, for evidence of treatment-related effects.
- Maternal body weight: recorded on day 0 and every 3 days from days 6 to 21 of gestation.
- Food consumption: recorded on days 6, 11, 16 and 21.

Ovaries and uterine content:

- On day 21 of gestation, the females were killed by an intrapulmonary injection of T61.
- Examination of uterine content: The uterus were removed and weighed. The uterine horns were then opened and the numbers of implantation and resorption sites and of live and dead fetuses were recorded.

Fetal examinations:

- Examination of fetuses: Live fetuses were removed, weighed, sexed, and examined for external anomalies including those of the oral cavity.
. Half of the viable fetuses from each litter were randomly selected, fixed in Bouin's solution, and examined microscopically as described by Barrow and Taylor for soft tissue anomalies.
. The remaining half of the fetuses were fixed in 70% ethanol and subsequently eviscerated, macerated in 1 % KOH, stained with Alizarin red S, and examined microscopically for skeletal anomalies.

Statistics:

- Whenever possible, the data were presented as means ± SD.
- Implantation sites, live fetuses and various body weights were analyzed by the one-way analysis of variance, followed by Dunnett's test if differences were found.
- The frequency of nonsurviving implants, resorptions and anomalies among litters was evaluated with the Dixon-Massey test after an arc-sine-square root transformation.
- Rates of pregnancy and fetal sex ratio were analyzed using Fisher's exact test.
- Where applicable, least-squares analysis was carried out. The reported level of statistical significance was p < 0.05.

Indices:

- absolute weight gain + gravide uterus weight
- pregnancy rate
- mean live fetuses per litter
- mean percentage of nonsurvviving implants per litter (resorption + dead fetuses)
- mean resorption sites per litter
- fetal sex ratio M:F
- mean fetal body weight per litt

Historical control data:

yes

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Description (incidence and severity):

No clinical signs attributed to treatment and no deaths were observed among treated females, in any dosed group.

Description (incidence and severity):

n/a

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

No significant effect on maternal body weight gain was noted in females given 25 or 50 mg/kg/day.
Maternal absolute weight gain was significantly decreased at 100 mg/kg/day compared to control.

Food consumption and compound intake (if feeding study):

not examined

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:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

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:

effects observed, treatment-related

Description (incidence and severity):

Significant increases in the mean percentage of nonsurviving implants and early embryonic resorptions were observed at 200 mg/kg/day (p < 0.05), concomitant with a non-significant decrease in the mean number of live fetuses per litter.

Dead fetuses:

not specified

Changes in pregnancy duration:

not specified

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

Pregnancy rates were equivalent across groups: around 90% in both treated and control groups.

Details on maternal toxic effects:

Treatment did not alter significantly the mean numbers of implantation sites, at any dose.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

> 200 mg/kg bw/day

Based on:

test mat.

Remarks on result:

not determinable due to absence of adverse toxic effects

Maternal abnormalities

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

Test substance induced a dose-related reduction in both male and female fetal weights which were significantly different from the control at 100 and 200 mg/kg/day (p < 0.05 and p < 0.01, respectively). Indeed, DPTU produced foetoxicity which characterized by significant decreases in fetal weight in a dose-related manner.

Description (incidence and severity):

n/a

Changes in sex ratio:

no effects observed

Description (incidence and severity):

The male-to-female sex ratio was comparable across groups (around 1 in both treated and control groups).

Changes in litter size and weights:

effects observed, treatment-related

Description (incidence and severity):

n/a

External malformations:

not specified

Skeletal malformations:

no effects observed

Description (incidence and severity):

no specific pattern of malformation was distinguished and the incidences of the skeletal variants were comparable to that of controls.

Visceral malformations:

effects observed, treatment-related

Description (incidence and severity):

A treatment-related increase in the incidence of subcutaneous cranial hemorrhage occurred at 200 mg/kg/day.
Apart from hemorrhage, single occurrences of craniorachischisis and gastroschisis, omphalocele, anophthalmia or microphthalmia, and diaphragmatic hernia were observed in treated groups.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Remarks:

(fetotoxicity)

Effect level:

50 mg/kg bw/day

Basis for effect level:

reduction in number of live offspring

2

Dose descriptor:

NOAEL

Remarks:

(embryotoxicity)

Effect level:

100 mg/kg bw/day

Basis for effect level:

fetal/pup body weight changes

3

Dose descriptor:

NOAEL

Remarks:

(teratogenicity)

Effect level:

> 200 mg/kg bw/day

Remarks on result:

not determinable due to absence of adverse toxic effects

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

DPTU was not teratogenic in rats in test conditions but embryolethal and fetotoxic at the doses of 100 and 200 mg/kg bw /day in absence of maternotoxicity.
The NOAEL for developmental toxicity is 50 mg/kg bw.

Executive summary:

Groups of 20 female rats were exposed at 0, 25, 50, 100 and 200 mg/kg of DPTU by gavage from Days 6 to 20 of gestation.

No clinical signs attributed to treatment and no deaths were observed among treated females, in any dosed group. No significant effect on maternal body weight gain was noted in females given 25 or 50 mg/kg/day. Maternal absolute weight gain was significantly decreased at 100 mg/kg/day compared to control. The NOAEL for maternal effet is 200 mg/kg bw because no major effect was observed at any dose.

The male-to-female sex ratio was comparable across groups (around 1 in both treated and control groups).

Treatment did not alter significantly the mean numbers of implantation sites, at any dose. Significant increases in the mean percentage of nonsurviving implants and early embryonic resorptions were observed at 200 mg/kg/day (p < 0.05), concomitant with a nonsignificant decrease in the mean number of live fetuses per litter. Test substance induced a dose-related reduction in both male and female fetal weights which were significantly different from the control at 100 and 200 mg/kg/day (p < 0.05 and p < 0.01, respectively). Therefore the NOAEL for foetoxicity effects is 50 mg/kg bw.

Moreover, embryofetal malformations were observed in the treated groups. A treatment-related increase in the incidence of subcutaneous cranial hemorrhage occurred at 200 mg/kg/day. Apart from hemorrhage, single occurrences of craniorachischisis and gastroschisis, omphalocele, anophthalmia or microphthalmia, and diaphragmatic hernia were observed in treated groups. However no specific pattern of malformation was distinguished and the incidences of the skeletal variants were comparable to that of controls.

No sign of teratogenicity was observed in this study (NOAEL for teratogenicity > 200 mg/kg bw).

To sum up, DPTU was not teratogenic in rats in test conditions but embryolethal and fetotoxic. The NOAEL for developmental toxicity is 50 mg/kg bw.