Isobutylamine

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

No food consumption measured, while a deviation from standard reproductive toxicity testing, considered to be acceptable deviation.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Isopropylamine

EC Number:

200-860-9

EC Name:

Isopropylamine

Cas Number:

75-31-0

Molecular formula:

C3H9N

IUPAC Name:

propan-2-amine

Test material form:

liquid: volatile

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

- Age (males): 10 weeks
- Weight at day 0 of gestation (females): 214-282 g
- Weight at day 0 of gestation (males): 317-389 g
- Number of animals: 25 females/group
25 Males/group
25 mated females7group
- Thirty air changes per hour

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

air

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus:
The exposure system consisted of 10 m3 glass and stainless steel New York University-style inhalation chambers and an atmospheric generation system.
- Method of holding animals in test chamber:
Mated animals were individually housed in suspended wire-bottom, stainless steel cages. All wire-inhalation cages were used during exposure.
- Source and rate of air: Air from the central ventilation supply was nominally maintained at 2030 liters per minute.
- System of generating particulates/aerosols: Test material atmospheres were generated using a Laskin-style nebulizer.
- Temperature, humidity, pressure in air chamber: 72+2 ‘F and 40-60% relative humidity.
- Air flow rate: 2030 litre/ minutes


TEST ATMOSPHERE
- Brief description of analytical method used:
Exposure chamber environment was monitored for isopropylamine concentrations at least five times per day in all chambers except the control. The control chamber was checked for the presence of test material twice during the study . Analytical measurements were made using a Miran lA General Purpose Gas Analyzer. The nominal concentration of each exposure level was determined five times per test chamber per day as the net amount of test material entering the air inlet of the inhalation chamber divided by chamber airflow per unit time.
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- Method: Gas analyser
- Sampling time: at least 5 times/day (treatment); the control was checked for the presence of test material
twice during the study

Details on mating procedure:

- Mating: 1 female / 1 male
- Day 0 of gestation: presence of vaginal plug

Duration of treatment / exposure:

- Gestation days 6 -15

Frequency of treatment:

6 hours /day

Duration of test:

- Twenty days, Cesarean section on gestation day 20

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

50 mg/m³ air (nominal)

Doses / concentrations 2

Dose / conc.:

500 mg/m³ air (nominal)

Doses / concentrations 3

Dose / conc.:

1 000 mg/m³ air (nominal)

Doses / concentrations 4

Dose / conc.:

50 mg/m³ air (analytical)

Remarks:

stable and homogeneous (within 4% difference between chamber locations)

Doses / concentrations 5

Dose / conc.:

499 mg/m³ air (analytical)

Remarks:

stable and homogeneous (within 4% difference between chamber locations)

Doses / concentrations 6

Dose / conc.:

1 000 mg/m³ air (analytical)

Remarks:

stable and homogeneous (within 4% difference between chamber locations)

No. of animals per sex per dose:

20 females

Control animals:

yes, concurrent no treatment

Examinations

Maternal examinations:

- Mortality: twice daily
- Clinical observations: on gestation days 0 and 6-20 (on treatment days after exposure)
- Body weight gain: gestation days 0, 6, 10, 13, 16 and 20
- Food consumption: not measured

ORGANS EXAMINED AT NECROPSY (MACROSCOPIC AND MICROSCOPIC):
- Macroscopy: findings dams recorded
- Microscopy: not performed

Ovaries and uterine content:

- Examination of uterine content: number of corpora lutea; relative position and number of live and dead foetuses and early and late resorptions

Fetal examinations:

- Examination of fetuses: sex; weight; external, visceral (1/2 of each litter) and skeletal (1/2 of each litter) findings

Statistics:

- Dunnett's test; Mann-Whitney U test; Fisher's Exact test

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical signs of rales, labored breathing and vaginal discharge (one female) were uniquely obse~ed in the high exposure level maternal animals. Sneezing was observed in both the high and mid exposure groups with higher incidence in the high exposure group. Fur staining/encrustation/nasal discharge was obsened at a higher incidence in the high exposure group maternal animals than the other exposure groups or the control group. During exposure, clear nasal discharge was observed in the high exposure group and sneezing was observed in the high exposure group and occasionally in the mid exposure group.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight(gain): decreased at 1000 mg/m3 on gestation days 10, 13, 16 and 20 and during day 6-20;
at 500 mg/m3, lower gains during gestation days 6-10 and overall 6-20

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:

effects observed, non-treatment-related

Description (incidence and severity):

Most females did not have remarkable postmortem findings in the exposure groups or the control group. Hydronephrosis, kidney stones and dilated ureters were observed in a few females but these findings were not considered to be treatment related because the incidence level was low and no dose response pattern was observed. Reduced abdominal fat was observed in two mid exposure group females and nine high exposure group females. No such findings were recorded for the control group or low exposure group females.

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:

effects observed, treatment-related

Description (incidence and severity):

Pre-implantation loss no differences;
post-implantation loss, at 500 mg/m3 slightly increased (1.0/dam vs 0.6/dam in the control)

Total litter losses by resorption:

effects observed, treatment-related

Description (incidence and severity):

at 500 mg/m3: slightly increased (1.0/dam vs 0.6/dam in the control)

Early or late resorptions:

effects observed, non-treatment-related

Description (incidence and severity):

No statistically significant differences were observed between any of the exposure groups for late resorption . Early resorption and consequently postimplantation loss were slightly elevated above control values in the mid exposure group (mean of l.O/dam vs. 0.6/dam); the difference was not statistically significant at the 5% confidence level with the Bonferroni inequality. Early resorption for the high and low exposure groups were not statistically different from the control value.

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

no effects observed

Effect levels (maternal animals)

1

Dose descriptor:

NOAEC

Effect level:

500 mg/m³ air

Based on:

test mat.

Basis for effect level:

other: matrenal toxicity

2

Dose descriptor:

NOEC

Effect level:

50 mg/m³ air

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

reduced ossification of the 13th rib and bent ribs at the high dose group without clear evidence of a dose-response (not significant)

Visceral malformations:

no effects observed

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
- Sex ratio: no differences
- Body weight gain: no differences
- External abnormalities: no treatment-related differences
- Visceral abnormalities: no treatment-related differences
- Skeletal abnormalities: reduced ossification of the 13th rib and bent ribs at the high dose group
without clear evidence of a dose-response (not significant)

Effect levels (fetuses)

Dose descriptor:

NOAEC

Effect level:

1 000 mg/m³ air

Based on:

test mat.

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

no effects observed

Overall developmental toxicity

Developmental effects observed:

no

Applicant's summary and conclusion

Conclusions:

The study did not produce evidence of a teratogenic response in female Sprague-Dawley rats exposed by the inhalation route to levels up to 1000 mg/m3 during the period of major organogenesis.

Executive summary:

Twenty-five mated females/group were exposed to atmospheres of isopropylamine (Lot Number LP-606, 99.77% pure) for 6 hours/day on days 6 through 15 of gestation.

Mean analytical exposure concentrations were O, 50, 499, and 1000 mg/m3.

All mated females were observed twice daily for mortality and examined on gestation days O and 6 through 20. Animals were also observed during exposure for gross signs of toxicity. Body weights were recorded on gestation days O, 6, 10, 13, 16, and 20. All females were sacrificed on gestation day 20. The uterus and ovaries were examined, and the ntiers and locations of live and dead fetuses, early and late resoptions, and copora lutes were recorded.

Gross pathology examinations were performed on all females. Fetuses were weighed, sexed, and examined for external malformations. Approximately one-half of the fetuses from each litter were given a visceral examination, and the remaining fetuses were examined for skeletal abnormalities.

No animals died during the study. However, clear indications of maternal toxicity were noted at the high exposure level as evidenced by reduced body weights (12 to 16% lower than controls), and signs of respiratory difficulties.

Slight toxicity was noted at the mid exposure level as indicated by reduced body weight gains for gestation days 6 through 10 and the overall period of gestation days 6 through 20. There was no apparent maternal toxicity at the low exposure level.

There were no treatient-related differences in pregnancy rates, pre- and postimplantation losses, fetal weights, or sex distribution.

At the high exposure level, the numbers of fetuses and litters with reduced ossification of the 13th ribs was increased. The value was not statistically significant when the nutier of affected litters was compared to the control group, but the incidence was outside the range of WIL Research Laboratories historical data. Reduced ossification, however, is considered to be a manifestation of growth retardation. Other manifestations of growth retardation, such as reduced ossification of sternebrae and vertebrae and decreased fetal body weights (a sensitive indicator), did not occur in this study. Thus , it appears that the decreased rib ossification was sporadic and not trea~ent-related.

One fetus in the high exposure level had bent liti bones (tibia and fibula), the only malformation of this type in the study. This fetus, as well as seven others in the same litter, had bent ribs, which are classified as variations.

However, only one other high exposure level fetus (in a different litter) had bent ribs, and the percentage of litters affected (8.3) was within the WIL historical control range (0.0 to 10.5%). Therefore, there was insufficient evidence to conclude that these findings were treatment-related. All other variations and malformations occurred sporadically across all groups.