2,2'-bipyridyl

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

unsuitable test system

Remarks:

irrelevant route of exposure.

Data source

Reference

Reference Type:

publication

Title:

Limb anomalies produced by 2,2'-dipyridyl in rats

Author:

Oohira A, Nogami H

Year:

1978

Bibliographic source:

Teratology. 1978, 18(1):63-70,

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Female rats were treated with the test item (at 60 or 75 mg/kg bw) by intraperitoneal injection on gestation day 11.5, 12.5, 13.5, or 14.5. On gestation day 21, dams were sacrificed, the fetuses were removed, weighed, and examined externally. Fetuses were macerated and the cartilaginous skeleton was examined after staining with methylene blue.
Additionally, limb buds of fetuses removed 10 and 20 h after administration of the test item on day 12.5 were examined microscopically.

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,2'-bipyridyl

EC Number:

206-674-4

EC Name:

2,2'-bipyridyl

Cas Number:

366-18-7

Molecular formula:

C10H8N2

IUPAC Name:

2,2'-bipyridine

Details on test material:

- Name of test material (as cited in study report): 2,2'-Dipyridyl (DIP)

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: about 250 g

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24°C
- Humidity (%): 55%
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

ethanol

Remarks:

25%

Details on exposure:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 60 and 75 mg/kg bw
- Concentration (if solution): at 60 mg/kg bw: 20 mg/mL, at 75 mg/kg bw: 25 mg/mL,

VEHICLE
- Concentration (if solution): 25%

Analytical verification of doses or concentrations:

no

Details on mating procedure:

- Impregnation procedure: cohoused
If cohoused:
- M/F ratio per cage: 1/1
- Length of cohabitation: overnight
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy

Duration of treatment / exposure:

Dams were killed on gestation day 21 after single exposure to the test item on gestation day 11.5, 12.5, 13.5, or 14.5.

Frequency of treatment:

single exposure

Duration of test:

Dams were killed on gestation day 21.

No. of animals per sex per dose:

5, 6, or 10 litters (dams) per concentration and treatment day (see also table 1).

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

CLINICAL OBSERVATIONS: Yes

MORTALITY: Yes

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: No

Fetal examinations:

- External examinations
- Skeletal examinations
- Fetal weight
- Mortality / resorptions

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
Neither maternal mortality nor clinical signs of toxicity occurred with the dosage used.

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Fetal death or resorption rates following maternal treatment with 2,2’-bipyridine were dependent on dose and administration time. The respective data are summarized in table 1. Briefly, treatment with higher doses or earlier in pregnancy resulted in higher mortality rates.
Fetal weight was also affected by administration of 2,2’-bipyridine, mean fetal wet weight gradually decreasing with later treatment (table 1).
Common external malformations produced in 21-day fetuses are listed and quantified in table 2. Most defects were seen in the limb. Few malformations were found in the cranial and costal bones or in the spinal column.
Digital defects were produced in the forelimbs of surviving fetuses in 97% by treatment with 60 mg/kg on day 12.5, and in 100% by treatment with 75 mg/kg on the same day. Digital defects in the hindlimbs in 70% and 86% of fetuses resulted from treatment with 75 mg/kg on gestation day 12.5 and 13.5, respectively, where missing or fusion of digits 3 and/or 4 was the most common defect. Fusion and shortening of tibia and fibula was almost uniquely produced by treatment on gestation day 12.5.
Ten hours after injection of 2,2’-bipyridine, large vacuoles containing dense granules were found in the cytoplasm of some mesenchymal cells in the forelimb bud of treated embryos; some of the granules in the vacuole fused with each other and showed amorphous structure. These vacuoles were not found in control tissue.
Twenty hours after treatment, mesenchymal condensations to form digital rays were not found while they were observed in the forelimb buds of control animals. Destruction of mesenchymal cells was evident, especially in the axial area of the treated limb bud.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Table 1: The effects of single administration of 2,2’-bipyridine to pregnant rats on litter size and mortality.

Treatment on GD	Dose [mg/kg bw]	No. litters	Mortality [%]	No. live fetuses	Wet weight [g]
11.5	60	5	59	23	4.92±0.23
12.5	0	5	6	59	5.39±0.14
	60	10	18	87	4.57±0.17
	75	6	58	30	4.10±0.21
13.5	75	6	46	42	4.08±0.36
14.5	75	5	43	36	3.84±0.62

GD: gestation day

 

Table 2: The effects of single administration of 2,2’-bipyridine to pregnant rats on embryonal malformations [%].

Treatment on GD	Dose [mg/kg bw]	Cleft palate	Digital malformations		Fusion of tibia and fibula
			Forelimb	Hindlimb
11.5	60	0	9	0	0
12.5	0	0	0	0	0
	60	11	97	14	9
	75	33	100	70	77
13.5	75	7	5	86	0
14.5	75	17	0	0	0

GD: gestation day

 

Applicant's summary and conclusion

Conclusions:

Intraperitoneal application of 2,2'-bipyridine to pregnant rats resulted in distinct malformations in the fetuses. Pattern of malformation was dependent on dose and application time (gestation day). Abnormalities were mainly observed in the limbs of fetuses. Microscopic evaluation revealed destruction (autophagocytosis) of mesenchymal stem cells.

Executive summary:

Developmental toxicity of 2,2’-bipyridine was assessed by intraperitoneal application of the test item (at 60 or 75 mg/kg bw) into pregnant rats on gestation day 11.5, 12.5, 13.5, or 14.5. On gestation day 21, dams were sacrificed; the fetuses were removed, weighed, and examined externally. Fetuses were macerated and the cartilaginous skeleton was examined after staining with methylene blue.

Additionally, limb buds of fetuses removed 10 and 20 h after administration of the test item on day 12.5 were examined microscopically.

Intraperitoneal application of 2,2'-bipyridine to pregnant rats resulted in distinct malformations in the fetuses. Pattern of malformation was dependent on dose and application time (gestation day). Abnormalities were mainly observed in the limbs of fetuses. Microscopic evaluation revealed destruction (autophagocytosis) of mesenchymal stem cells.