2-methylbutan-2-ol

Developmental toxicity / teratogenicity

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well described publication and suitable for assessment.

Data source

Reference

Reference Type:

publication

Title:

The effects of prenatal tertiary butanol administration in CBA/J and C57BL/6J mice

Author:

Faulkner TP, Wiechart JD, Hartman DM, Hussain AS

Year:

1989

Bibliographic source:

Life Sciences, volume 45, pages 1989-1995

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Pregnant mice were given tertiary butanol by gavage twice daily from day 6 through day 18 of gestation. Examinations were made on day 18.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Automatically generated during migration to IUCLID 6, no data available

IUPAC Name:

Automatically generated during migration to IUCLID 6, no data available

Details on test material:

- Name of test material (as cited in study report): tertiary butanol

Test animals

Species:

mouse

Strain:

other: CBA/J and C57BL/6J

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Jackson Laboratories, Bar Harbor, ME, USA
- Age at study initiation: 25 - 30 weeks
- Diet: standard lab chow; ad libitum
- Water: ad libitum

Administration / exposure

Route of administration:

oral: gavage

Type of inhalation exposure (if applicable):

not specified

Vehicle:

water

Analytical verification of doses or concentrations:

no

Details on mating procedure:

- Impregnation procedure: cohoused
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug day 0 of pregnancy

Duration of treatment / exposure:

13 days (from day 6 through day 18 of gestation.)

Frequency of treatment:

twice a day (every 12 hour)

Duration of test:

The female mice were sacrificed on day 18 by decapitation.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
20 mL/kg bw /day of a 10% (v/v) solution
Basis:
other: nominal conc. 20 ml/kg bw of a 10% (v/v) solution every 12 hours

Doses / concentrations 2

Remarks:

Doses / Concentrations:
21 mmoles / kg bw /day = 1556 mg/kg bw/day
Basis:
other: nominal conc. 10.5 mmoles/ kg bw (=778 mg/ kg bw every 12 hours)

No. of animals per sex per dose:

CBA/J control: 7 females
CBA/J t-butanol: 12 females
C57BL/6J control: 5 females
C57BL/6J t-butanol: 9 females

Control animals:

yes, concurrent vehicle

Examinations

Ovaries and uterine content:

- Number of implantations: Yes
- Number of resorptions: Yes
- Number of live fetuses: Yes

Fetal examinations:

- External examinations: no data
- Soft tissue examinations: Yes (half per litter)
- Skeletal examinations: Yes (half per litter)
- Head examinations: no data
- Mean fetal weight: Yes (all per litter)

Statistics:

A two way analysis of variance (strain x treatment) was used in comparing the mean numbers of viable fetuses, resorptions and abnormalities per litter between treatment groups. Treatment effects on fetal weight within each strain were analyzed by Student's t test. Chi2-Yates was used to compare the number of litters with resorptions or 100% resorptions between treatment groups.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no data

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
The effects of t-butanol treatment on fetal resorptions and the weight of the surviving fetuses: Tertiary butanol produced a significant increase in the number of resorptions per litter, F(1,29)=7.361, p.=0.011, and a significant decrease in the number of live fetuses per litter, F(1,29)=10.060, p.=0.004. There were no significant effects of strain on either the number of resorptions per litter, F(1,29)=0.07, p.=0.787, or the
number of live fetuses per litter, F(1,29)=0.322, p.=0.575. Eight of the 21 litters in the t-butanol treated groups had all of the fetuses resorbed vs.
none in the control groups (X2=4.10, p.<0.05). Significantly more of the resorptions in the treated groups (33/75) required ammonium sulfide for
visualization than in the control groups (2/14) (X2=4.66, p.<0.05), suggesting an early effect on fetal viability. No inter-strain differences in fetal
mortality were observed. There was a slight but statistically insignificant decrease in the weight of the surviving fetuses in both strains.
The results of morphological examination of the surviving offspring: Soft tissue examination revealed no teratogenic effects of t-butanol in either strain. There was no evidence that t-butanol produced the dilated ventricles, open eyelids, exencephaly, heart defects, or gastroschisis reported for ethanol in the CBA/J strain (27), even though fetuses were carefully examined for these defects. Skeletal examinations showed defects limited to the skull and sternum. Minor variations (misaligned or underossified sternebrae and underossified supraoccipital bones) occurred more frequently, but were not significantly different between treatments or strains.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

>= 1 556 mg/kg bw/day

Basis for effect level:

other: teratogenicity

2

Dose descriptor:

LOAEL

Effect level:

1 556 mg/kg bw/day

Basis for effect level:

other: embryotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The developmental toxicity was tested in a read-across study with tertiary butanol. The NOAEL based on teratogenicity was determined to be >= 1556 mg/kg bw/day.

Executive summary:

The developmental toxicity was tested in a read-across study with tertiary butanol. Pregnant mice were given tertiary butanol by gavage twice daily from day 6 through day 18 of gestation. Examinations were made on day 18. The females were sacrificed on day 18 by decapitation. The following concentrations were used: 20 mL/kg bw/day of a 10 % (v/v) solution equivalent to 1556 mg/kg bw/day (Basis=nominal conc. 10.5 mmoles/kg bw (=778 mg/kg bw every 12 hours). Two different strains were used to determine the toxicity: CBA/J (7 females control and 12 females test item) and C57BL/6J (5 females control and 9 females test item). The ovaries and uterine content was examined by determining the number of implantations, the number of resoprtions and number of live fetuses. Also fetal examinations were performed by determining soft tissue examinations, skeletal examinations and the mean fetal weight. As a result the NOAEL was determined to be >= 1556 mg/kg bw/day based on teratogenicity. The LOAEL was determined to be 1556 mg/kg bw/day based on embryotoxicity. No maternal toxicity was observed during the study. Tertiary butanol produced a significant increase in the number of resorptions per litter, F(1,29)=7.361, p.=0.011, and a significant decrease in the number of live fetuses per litter, F(1,29)=10.060, p.=0.004. There were no significant effects of strain on either the number of resorptions per litter, F(1,29)=0.07, p.=0.787, or the number of live fetuses per litter, F(1,29)=0.322, p.=0.575. Eight of the 21 litters in the t-butanol treated groups had all of the fetuses resorbed vs.none in the control groups (X2=4.10, p.<0.05). Significantly more of the resorptions in the treated groups (33/75) required ammonium sulfide for visualization than in the control groups (2/14) (X2=4.66, p.<0.05), suggesting an early effect on fetal viability. No inter-strain differences in fetal mortality were observed. There was a slight but statistically insignificant decrease in the weight of the surviving fetuses in both strains. The results of morphological examination of the surviving offspring: Soft tissue examination revealed no teratogenic effects of t-butanol in either strain. There was no evidence that t-butanol produced the dilated ventricles, open eyelids, exencephaly, heart defects, or gastroschisis reported for ethanol in the CBA/J strain (27), even though fetuses were carefully examined for these defects. Skeletal examinations showed defects limited to the skull and sternum. Minor variations (misaligned or underossified sternebrae and underossified supraoccipital bones) occurred more frequently, but were not significantly different between treatments or strains.