Butan-1-ol

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:

guideline study

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

2005

Reference 2

Reference Type:

review article or handbook

Title:

An overview of butanol-induced developmental neurotoxicity and the potential mechanisms related to these observed effects

Author:

Bale AS and Lee JS

Year:

2016

Bibliographic source:

Neurotoxicology and Teratology 53 (2016) 33–40

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: Ministry of Health and Welfare, Japan; Guidelines for Toxicity Studies of Drugs

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Principles of method if other than guideline:

Pregnant rats were given drinking water containing 1-butanol at 0.2%, 1.0% or 5.0% (316, 1454 or 5654 mg/kg/day) on days 0–20 of pregnancy. The rats were sacrificed on day 20 of pregnancy and both the dams and fetuses were examined.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Butan-1-ol

EC Number:

200-751-6

EC Name:

Butan-1-ol

Cas Number:

71-36-3

Molecular formula:

C4H10O

IUPAC Name:

butan-1-ol

Test material form:

liquid

Test animals

Species:

rat

Strain:

Crj: CD(SD)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Tsukuba Breeding Center
- Age at study initiation: males: 10 weeks; females: 9 weeks
- Weight at study initiation: females: 217-273 g
- Housing: individually
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-25 °C
- Humidity (%): 40-70 %
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
1-butanol was mixed with water to the according target concentrations. The stability of formulations in a dark and cool place under airtight conditions has been confirmed for up to 3 days. During use, the formulations were maintained under such conditions for no more than 3 days and were 95.7–103.5% of the target concentration.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations were determined analytically and were 95.7–103.5% of the target concentration.

Details on mating procedure:

- Impregnation procedure: [cohoused]
- If cohoused:
- M/F ratio per cage: 1/1
- Length of cohabitation: over night
- 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:

day 0 through day 20 of pregnancy

Frequency of treatment:

continuous through drinking water

Duration of test:

until day 20 of pregnancy

No. of animals per sex per dose:

20 females per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dosage levels were determined based on the results of our range-finding study in which administration of 1-butanol in the drinking water on days 0–20 of pregnancy caused decreases in maternal body weight gain and food and water consumption and tended to reduce in fetal weight at 4% and 7% in rats.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: not specified



DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: not not specified


BODY WEIGHT: Yes
- Time schedule for examinations: once daily


FOOD CONSUMPTION: Yes
- Time schedule for examinations: every 3 or 4 days


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: daily


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 10
- Organs examined: not specified

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]
- Head examinations: Yes: [half per litter]

Statistics:

The statistical analysis of fetuses was carried out using the litter as the experimental unit. The initial body weight, body weight gain and food and water consumption of pregnant rats, numbers of corpora lutea, implantations and live fetuses per litter, fetal weight and crown-rump length and placental weight were analyzed with Bartlett's test for homogeneity of variance at the 5% level of significance.
If it was homogeneous, the data were analyzed using Dunnett's multiple comparison test to compare the mean of the control group with that of each dosage group, and if it was not homogeneous, the mean rank of the 1-butanol-treated groups was compared with that of the control group with the Dunnett type test. The Dunnett type test was used for the incidences of pre- and postimplantation embryonic loss and fetal anomalies and sex ratio of fetuses to compare the mean rank of groups treated with 1-butanol and that of the control group. The incidence of dams with anomalous fetuses was analyzed by Chi-square test or Fisher's exact test. The significance of differences from the control group was estimated at probability levels of 1% and 5%.

Indices:

no data

Historical control data:

International Genetic Standard (Crj: CD (SD) IGS) rats were used throughout this study. This strain was chosen because it is most commonly used in reproductive and developmental toxicity studies and historical control data are available.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Details on maternal toxic effects:
No death was found in female rats of any group. All females in all groups became pregnant. The body weight gains on days 0–7 of pregnancy were significantly reduced at 5.0%. The body weight gain during the whole period of pregnancy was also significantly decreased at 5.0%. No significant decrease in the body weight gain was noted at 0.2 or 1.0, except for a transient decrease on days 0–2 of pregnancy at 1.0%. The food consumption on days 0–7, days 7–14, days 14–20 and days 0–20 of pregnancy was significantly lower in the 1.0% and 5.0% groups than the control group. The water consumption on days 0–7 at 1.0 and 5.0% and on days 7–14, days 14–20 and days 0–20 at 5.0% was significantly decreased. The mean daily intakes of 1-butanol were 316 mg/kg for the 0.2% group, 1454 mg/kg for the 1.0% group and 5654 mg/kg for the 5.0% group.

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Remarks:

maternal toxicity

Effect level:

1 454 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Details on embryotoxic / teratogenic effects:
No litters totally resorbed were found in any group. No effects of the administration of 1-butanol were observed on the numbers of corpora lutea, implantations, pre- or postimplantation loss, resorptions or dead or live fetuses or sex ratio of live fetuses. The body weights of male and female fetuses were significantly lower in the 5.0% group than in the control group. There was no significant difference in the crown-rump length of male and female fetuses or placental weight between the control and groups treated with 1-butanol.
One fetus with spina bifida in the control group and one fetus with thread-like tail and anal atresia in the 0.2% group were observed. Skeletal examination revealed one fetus with supernumerary thoracic vertebral bodies and malpositioned thoracic vertebrae at 1.0%. Although the total number of fetuses with skeletal variations was significantly increased at 5.0%, the number of fetuses with individual skeletal variations was not significantly increased, except for fetuses with short supernumerary ribs at 5.0%. A significantly lower number of forepaw proximal phalanges was observed at 5.0%. Membranous ventricular septum defect occurred in one fetus of the control and 0.2% groups and 3 fetuses in 3 dams of the 5.0% group. One fetus with a double aorta in the control group and one fetus with a left umbilical artery in the control and 2.0% groups were observed. Thymic remnants in the neck were found in 4–11 fetuses of the control and groups treated with 1-butanol.
However, there was no significant difference in the incidence of fetuses with internal abnormalities between the control and groups treated with 1-butanol.

Effect levels (fetuses)

1

Key result

Dose descriptor:

NOAEL

Remarks:

teratogenicity

Effect level:

5 654 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: teratogenicity

2

Key result

Dose descriptor:

NOAEL

Remarks:

developmental toxicity

Effect level:

1 454 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: fetotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

A significant decrease in maternal body weight gain accompanied by reduced food and water consumption was found at 5.0%. No significant increase in the incidence of pre- and postimplantation embryonic loss was observed in any groups treated with 1-butanol. Fetal weight was significantly lowered at 5.0%. Although a significant increase in the incidence of fetuses with skeletal variations and decreased degree of ossification was found at 5.0%, no increase in the incidence of fetuses with external, skeletal and internal abnormalities was detected in any groups treated with 1-butanol. The data demonstrate that 1-butanol is developmental toxic only at maternal toxic doses. No evidence for teratogenicity of 1-butanol was noted in rats. Based on the significant decreases in maternal body weight gain and fetal weight, it is concluded that the no observed adverse effect levels (NOAELs) of 1-butanol for both dams and fetuses are 1.0% (1454 mg/kg/day) in rats.

Table 1

Maternal findings in rats given 1-butanol on days 0–20 of pregnancy

Dose (%)	0 (Control)	0.2	1.0	5.0
No. of rats	20	20	20	20
No. of pregnant rats	20	20	20	20
No. of dead rats	0	0	0	0
Initial body weight	245 ± 14	247 ± 13	245 ± 11	244±12
Body weight gain during pregnancy (g)^a
Days 0–7	44 ± 7	45 ± 7	40 ± 6	20 ± 28**
Days 7–14	40±6	41±5	41±7	42±10
Days 14–20	78±14	82 ± 8	84 ± 7	75 ± 11
Days 0–20	162 ± 19	168 ± 16	165 ± 15	146 ± 16**
Food consumption during pregnancy (g)^a
Days 0–7	179 ± 12	180 ± 16	164 ± 12*	138 ± 21**
Days 7–14	193 ± 14	194 ± 17	177 ± 14**	160 ± 11**
Days 14–20	176 ± 14	175 ± 15	161 ± 12**	143 ± 11**
Days 0–20	548 ± 38	548 ± 46	503 ± 34**	441 ± 34**
Water consumption during pregnancy (ml)^a
Days 0–7	284 ± 28	305 ± 37	258 ± 29*	175 ± 34**
Days 7–14	318 ± 35	337 ± 48	299 ± 40	239 ± 80**
Days 14–20	328 ± 47	342 ± 47	334 ± 46	256 ± 85**
Days 0–20	930 ± 105	983 ± 126	890 ± 106	669 ± 182**
Mean daily intakes of 1-butanol (mg/kg)^a	0	316 ± 30	1454 ± 186	5654 ± 1402

** Significantly different from the control, *P< 0.05 and **P< 0.01.^aValues are given as the mean ± SD.

Table 2

Reproductive findings in rats given 1-butanol on days 0–20 of pregnancy

Dose (%)	0 (Control)	0.2	1.0	5.0
No. of litters	20	20	20	20
No. of litters totally resorbed	0	0	0	0
No. of corpora lutea per litter^a	16.4 ± 3.6	16.7 ± 3.0^d	16.1 ± 2.1	16.3 ± 2.6
No. of implantations per litter^a	14.3 ± 2.8	15.1 ± 1.7	15.2 ± 1.2	14.7 ± 2.5
% Preimplantation loss per litter^b	9.0	9.0d	4.4	9.2
% Postimplantation loss per litter^c	6.0	5.4	3.7	8.0
No. of live fetuses per litter^a	13.4 ± 2.6	14.3 ± 1.4	14.7 ± 1.5	13.5 ± 2.5
Sex ratio of live fetuses (male/female)	128/139	145/140	149/144	131/139
Body weight of live fetuses (g)^a
Male	4.18±0.27	4.00±0.24	4.04±0.25	3.83±0.18**
Female	3.97 ± 0.25	3.86 ± 0.20	3.83 ± 0.16	3.59 ± 0.17**
Fetal crown-rump length (mm)^a
Male	40.5 ± 1.2	40.3 ± 1.4	40.2 ± 1.2	39.7 ± 1.3
Female	39.4 ± 1.2	39.4 ± 1.2	39.3 ± 1.1	38.5 ± 1.4
Placental weight (g)
Male	0.50 ± 0.05	0.49 ± 0.05	0.48 ± 0.06	0.50 ± 0.06
Female	0.49 ± 0.05	0.48 ± 0.05	0.47 ± 0.05	0.49 ± 0.06

** Significantly different from the control, *P< 0.01

^aValues are given as the mean ± SD.

^b(No. of preimplantation embryonic loss/no. of corpora lutea)x100.

c(No. of resorptions and dead fetuses/no. implantations)x100.

^dValue was obtained from 19 pregnant rats.

Table 3

Morphological examinations in fetuses of rats given 1-butanol on days 0–20 of pregnancy

Dose (%)	0 (Control)	0.2	1.0	5.0
External examination
Total no. of fetuses (litters) examined	267(20)	285(20)	293(20)	270(20)
Total no. of fetuses (litters) with abnormalities	1 (1)	1 (1)	0	0
Spina bifida	1 (1)	0	0	0
Thread-like tail and anal atresia	0	1 (1)	0	0
Skeletal examination
Total no. of fetuses (litters) examined	139(20)	147(20)	152(20)	140(20)
Total no. of fetuses (litters) with abnormalities	0	0	1 (1)	0
Supernumerary of thoracic vertebral bodies and malpositioned thoracic vertebrae	0	0	1 (1)	0
Total no. of fetuses (litters) with variations	28(11)	23(12)	52(17)	69 (20)**
Bipartite ossification of thoracic centra	1 (1)	1 (1)	1 (1)	7(5)
Dumbbell ossification of thoracic centra	0	1 (1)	2(2)	3 (3)
Bipartite ossification of lumbar centra	0	0	0	2(2)
Supernumerary lumbar vertebrae	4(1)	1 (1)	5 (3)	5 (2)
Lumbarization	0	0	1 (1)	1 (1)
Bipartite ossification of sternebrae	1 (1)	1 (1)	1 (1)	1 (1)
Misaligned sternebrae	0	0	0	1 (1)
Cervical ribs	2(2)	3(3)	3 (3)	7(5)
Full supernumerary ribs	5(2)	1 (1)	10 (5)	9(5)
Short supernumerary ribs	20(10)	18 (9)	43(16)	55 (19)**
Wavy ribs	0	0	0	1 (1)
Degree of ossification^a
No. of sacral and caudal vertebrae	8.4 ± 0.5	8.4 ± 0.4	8.3 ± 0.5	8.1 ± 0.3
No. of sternebrae	5.9 ± 0.2	5.8 ± 0.2	5.8 ± 0.2	5.8 ± 0.2
No. of forepaw proximal phalanges	1.6 ± 1.3	1.6 ± 0.9	1.2 ± 1.1	0.3 ± 0.4**
Internal examination
Total no. of fetuses (litters) examined	128(20)	138(20)	141 (20)	130(20)
Total no. of fetuses (litters) with abnormalities	7(6)	9(6)	11 (8)	14(9)
Membranous ventricular septum defect	1 (1)	1 (1)	0	3 (3)
Double aorta	1(1)	0	0	0
Left umbilical artery	1 (1)	0	1 (1)	0
Thymic remnant in neck	4(4)	8 (5)	10 (8)	11 (8)

^aValues are given as the mean ± SD.

** Significantly different from the control, *P< 0.01