Bis(isopropyl)naphthalene

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 Jul. - 29 Oct. 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EU Method B.31 (Prenatal Developmental Toxicity Study)

Version / remarks:

; cited as Directive 87/302/EEC, part B, p. 24

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Bis(isopropyl)naphthalene

EC Number:

254-052-6

EC Name:

Bis(isopropyl)naphthalene

Cas Number:

38640-62-9

Molecular formula:

C16H20

IUPAC Name:

bis(isopropyl)naphthalene

Details on test material:

- Name of test material (as cited in study report): Di-isopropyl Naphthalene (KMC)
- Physical state: liquid
- Analytical purity: 99.7%
- Isomers composition: no data
- Purity test date: 04 Aug. 1992
- Lot/batch No.: 10532
- Stability under test conditions: stable
- Storage condition of test material: room temperature

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: SD Lippische Versuchstierzucht HAGEMANN GmbH, Extertal, Germany
- Age at study initiation: approx. 59 d
- Weight at study initiation: 204 - 294 g
- Fasting period before study: no
- Housing: individual in Macrolon cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 7 d


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +- 2
- Humidity (%): 50 +-15
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: sesame oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water): forms stable suspension with DIPN
- Amount of vehicle (if gavage): 5 mL/kg bw
- Purity: DAB 10

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

GC, Column: Chrompack 50 m x 0.25 mm, Coating CP-Wax-52 CB, 250 °C (FID), external standard calibration (Report, p. 219):
Recoveries of DIPN concentrations in test suspension were 90 - 107 %, independent of storage time during study duration.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1 / 1
- Length of cohabitation: overnight
- Further matings repeated if unsuccessful
- Proof of pregnancy: sperm in vaginal smear, referred to as day 0 of pregnancy

Duration of treatment / exposure:

day 6 to 15 of gestation

Frequency of treatment:

1x/d

Duration of test:

20 d

No. of animals per sex per dose:

20

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Doses for the main study were selected based on results of a range finding study using 2 pregnant rats dosed at 100, 350, 750, and 1000 mg/(kg bw*d)

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION): Yes, daily
- Time schedule for examinations: daily

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

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: gross pathology/necropsy (not specified)

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: sex, viability

Fetal examinations:

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

Statistics:

Analysis of variance: Homogeneity of variance for mean values using the Bartlett chi-square test, one-way analysis if appropriate, Dunnett test was used in cases of significant differences among groups. In case of heterogeneity, Student´s test was carried out. for comparison of malformations, retardation- and variation rates, the Fisher Exact test or chi-square test were employed.

Indices:

Corpera lutea per dam; implantations per dam; number of fetuses (alive and dead) per dam; resorptions per dam (early and late); pre- and post-implantation loss; runts per dam; malformations, variations per dam

Historical control data:

Average in-house data summarised for SD rats from 1988 - 1991 (Report, p. 214-217)

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
In dams, there was no substance-related mortality. No significant clinical or toxic symptoms were observed, except an disproportionate reduction in feed consumption in the mean and high-dose group, with approx. -15 % and -34 %, respectively, from gd 6 to gd 9 (p<0.01) [Report, Tab. 5, Fig. 2].
Body-weight and body-weight gain were within the normal range at all dose-groups, but a transient decline in body-weight gain after dosing (gd 6 - 9) at 250 and 625 mg/(kg*d) was observed (-26 % and -70% in the 250- and 625-mg group, respectively) [Report Tab. 3].
This transient body-weight loss paralleled the transient decrease in food uptake and was overcompensated by a disproportionate increase in body-weight gain during gd 12 - 15 as compared to the control and low dose treatment group.
Drinking-water consumption was not influenced by the treatment.
No remarkable findings on necropsy.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day (nominal)

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

LOAEL

Effect level:

250 mg/kg bw/day (nominal)

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
No adverse effects were observed even at the highest dose tested with incipient maternal toxicity.

Effect levels (fetuses)

Dose descriptor:

NOEL

Remarks:

(highest dose tested)

Effect level:

625 mg/kg bw/day (nominal)

Basis for effect level:

other: no effects observed

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Range finding study

 

Dose selection was based on the range-finding study using 2 pregnant rats dosed at 100, 350, 750 and 1000 mg/(kg bw*d). 100 and 350 mg/(kg bw*d) were well tolerated, while 750 mg/(kg bw*d) was within the incipient maternal and fetotoxic range.

 

Main study

 

No developmental toxicity was observed at the highest dose tested with incipient maternal toxicity.

 

Reproduction data:

Fertility rate: 95.5 % (control and 250-mg group)

                     100 % (100- and 625-mg group)

No significant differences from the control were noted in all reproductive parameters.

 

Resorption rates/post-implantation losses:

Controls:              11.9 %

100-mg group:       5.8 %

250-mg group:     10.1 % *

625-mg group:       9.4 %

  * including one dead fetus

No particular developmental adverse effects on the fetuses of any treatment group were observed, comprising physiological (body weight and body length) as well as morphological parameters (malformations and variations).

 

Autopsy findings: none

There were no fetal deaths but one in the 250-mg group.

Applicant's summary and conclusion

Conclusions:

The treatment of pregnant rats produced no pathologically relevant effects, neither in the dams nor in the offspring. The authors´ conclusion (p. 13 and 29) of a very slight trend towards an increased incidence of skeletal retardation at the mid and high dose level is not evident from the results tables.

Transient significant reduction in feed consumption and body weight gain were observed during maternal development.

With respect to the maternal body-weight effect, the NOAEL for maternal toxicity is assumed to be 100 mg/(kg*d). Due to the absence of embryotoxic effects, the highest dose, 625 mg/(kg*d), corresponds to a NOEL for developmental effects (embryo-/fetotoxicity and teratogenicity).