Registration Dossier

Toxicological information

Developmental toxicity / teratogenicity

Currently viewing:

Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study well documented, meets generally accepted scientific principles, acceptable for assessment
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1996

Materials and methods

Principles of method if other than guideline:
In developmental toxicity study, pregnant murine strain (LM/Bc) mice were injected intraperitoneally with sodium arsenate at 40 mg/kg bw during gestation day (GD) 7:12 (day:hour) and 8:12. Control group animals were injected with physiologic saline. Neural tubes were then isolated from both control and arsenic treated embryos at GD 9:00, 9:12, 10:00, and 10:12, which encompasses all the stages of neurulation for this murine strain. Using the molecular techniques of in situ transcription and antisense RNA amplification (RT/aRNA) the expression pattern for bc1-2, p53, wee-1 and wnt-1 was analyzed at each of these time points.
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Sodium arsenate
- Source: Sigma chemicals, St.Louis, MO

Test animals

Species:
mouse
Strain:
other: murine strain (LM/Bc/Fnn)

Administration / exposure

Route of administration:
intraperitoneal
Vehicle:
other: Physiologic saline
Analytical verification of doses or concentrations:
not specified
Details on mating procedure:
- Impregnation procedure: Cohoused, pathogen free virgin females 50-70 days of age were mated with experienced males
- Length of cohabitation: Overnight
- Proof of pregnancy: Presence of vaginal plug (0 day:12 hours)
Duration of treatment / exposure:
2 days (on day 7:12 hours and day 8:12 hours)
Frequency of treatment:
2 days
Duration of test:
10 gestation days
Doses / concentrations
Remarks:
Doses / Concentrations:
40 mg/kg bw
Basis:
actual ingested
No. of animals per sex per dose:
No data
Control animals:
yes, concurrent vehicle

Results and discussion

Results: maternal animals

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
40 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
other: other:
Remarks on result:
not determinable
Remarks:
no NOAEL identified

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes. Remark: exencephaly in fetus and neural tube defects in embryos

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Table 1:Relative gene expression values for each cell cycle gene from the isolated neural tubes of LM/Bc embryos during neurulation

Gene

Gestational day

9:00

9:12

10:00

10:12

Control

Arsenic

Control

Arsenic

Control

Arsenic

Control

Arsenic

bc1-2

1.307±0.11

1.858±0.11*

1.763±0.10a

1.694±0.12

1.365±0.06

1.190±0.04

1.261±0.04

1.383±0.07

p53

1.191±0.08

1.763±0.07*

1.931±0.17a

2.00±0.16

1.266±0.08

1.194±0.06

0.998±0.03

1.071±0.04

wee-1

1.166±0.09b

0.753±0.05

1.795±0.21

1.385±0.10

2.526±0.22

2.576±0.24

2.947±0.27

3.822±0.38

wnt-1

0.923±0.35c

0.855±0.04

1.006±0.06

0.993±0.05

1.235±0.04

1.272±0.06

1.181±0.05

1.304±0.06

 

Data are shown as mean±SEM

* Significantly different than control values, p<0.05

aSignificantly greater than control values at the other time points for this gene, p<0.05

bSignificantly less than control values at the other time points for this gene, p<0.05

cSignificantly less than control values at 10:00 and 10:12 for this gene, p<0.05

 

 

 

Applicant's summary and conclusion

Conclusions:
Under the test conditions, arsenic induces the neural tube defects in exposed embryos of murine strain (LM/Bc) mice.
Executive summary:

In developmental toxicity study, pregnant murine strain (LM/Bc) mice were injected intraperitoneally with sodium arsenate at 40 mg/kg bw during gestation day (GD) 7:12 (day:hour) and 8:12. Control group animals were injected with physiologic saline. Neural tubes were then isolated from both control and arsenic treated embryos at GD 9:00, 9:12, 10:00, and 10:12, which encompasses all the stages of neurulation for this murine strain. Using the molecular techniques of in situ transcription and antisense RNA amplification (RT/aRNA) the expression pattern for bc1-2, p53, wee-1 and wnt-1 was analyzed at each of these time points.

Treatment of sodium arsenate causes exencephaly in 90 to 100% of the exposed fetuses. In the neural tubes isolated from control embryos, the expression of all four genes (bc1-2, p53, wee-1, and wnt-1) were significantly altered as neurulation progressed, demonstrating their developmental regulation. Following arsenate treatment, however, there was a significant upregulation in the expression of bc1-2 and p53 at gestational day 9:00, compared to their control values. The heightened expression of both these genes suggests that arsenic inhibits cell proliferation, rather than inducing apoptosis, which delayed neural tube closure and led to the neural tube defects in exposed embryos.

Under the test conditions, arsenic induces the neural tube defects in exposed embryos of murine strain (LM/Bc) mice.