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Toxicological information

Developmental toxicity / teratogenicity

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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:
other: GLP compliant, guideline study, available as unpublished report, no restrictions, fully adequate for assessment
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1997
Report Date:
1997

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)
Deviations:
not specified
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 2,4,4-trimethylpentene (also known as diisobutylene and diisobutene)
- Physical state: clear, colourless liquid
- Analytical purity: 95.19%
- Lot/batch No.: Batch No. 2 (a 50:50 mixture of two original batches of 2,4,4-trimethylpentene - the details of which are as follows: Batch No. R11 supplied by Shell and Batch No. 155833 supplied by Erdolchemie).
- Expiration date of the lot/batch: 29 April 1997
- Storage condition of test material: Under nitrogen, protected from light, in a cool store.

Test animals

Species:
rat
Strain:
other: CD (Sprague-Dawley origin)
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River (UK) Limited, Margate, Kent, England
- Age at study initiation: 11-12 weeks
- Weight at study initiation: 229-262 g
- Housing: Individually in stainless steel or high density polypropylene cages.
- Diet: pelleted rodent diet (LAD 1 SQC, from Special Diets Services Limited, Witham, Essex, England ad libitum
- Water: Tap water ad libitum
- Acclimation period: 12 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19.5-21.5°C
- Humidity: 49-74%
- Air changes: Approximately 15/hr
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 24 June 1996 To: 9 August 1996

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
maize oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
- The formulation for the high dosage group (Group 4) was prepared by mixing the test material with maize oil. The formulations for the other treated groups were prepared by serial dilution of the Group 4 formulation.
All efforts were taken to minimise vaporisation of the test material during the formulation procedure.

VEHICLE
- Concentration in vehicle: Prepared at the appropriate concentration in maize oil to permit administration at a constant volume-dosage of 5 mL/kg.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Homogeneity, stability and achieved concentrations of the formulations were measured throughout the study.
Details on mating procedure:
- Impregnation procedure: cohoused
- M/F ratio per cage: 1:1
- Length of cohabitation: 6 days
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug and/or sperm in vaginal smear; referred to as day 0 of pregnancy
- Any other deviations from standard protocol: males and females paired on the fifteenth day of treatment.
Duration of treatment / exposure:
Dosing was for 15 days before pairing. Treatment was continued throughout mating, gestation and lactation to Day 3 of lactation.
Frequency of treatment:
Daily
Duration of test:
Until offspring were 4 days old.
No. of animals per sex per dose:
10
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Based on the results of a preliminary seven-day toxicity study performed at these laboratories in which no evidence of toxicity was apparent at dosages up to and including 1000 mg/kg bw/day.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily during weeks 1-2, weekly during weeks 3-6

BODY WEIGHT: Yes
- Time schedule for examinations: Females were weighed on the day that treatment commenced, at weekly intervals until mating was detected, on Days 0, 7, 14 and 20 of gestation and on Days 1 and 4 of lactation.

FOOD CONSUMPTION : Yes
- Food consumption (by cage) determined until pairing and mean weekly diet consumption calculated as g food/kg body weight/day: Yes
- Food consumption for females was also recorded for the periods Days 0-3, 4-6, 7-10, 11-13, 14-16 and 17-19 of gestation and for the period Days 1-3 of lactation.

POST-MORTEM EXAMINATIONS: Yes
Ovaries and uterine content:
- The number of corpora lutea and uterine implantation sites were recorded in all females. Uterus and cervix were weighed.
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: No
- Skeletal examinations: No
- Head examinations: No
Statistics:
Absolute bodyweights at the start of each phase, bodyweight gains, food consumption values and litter sizes were assessed by one-way analysis of variance. Whenever this was found to be significant, a Student's 't'-test was used. For organ weights, homogeneity of variance was automatically tested using Bartlett's test. Whenever this was found to be statistically significant a Behrens-Fisher test was used to perform pair-wise comparisons, otherwise a Dunnett's test was used. Inter-group differences in offspring survival, sex ratio and macroscopic pathology and histopathology were assessed, on indication, using Fisher's Exact test.
Indices:
Offspring viability indices: pre-implantation survival index; post-implantation survival index; live birth index; viability index.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
CLINICAL SIGNS AND MORTALITY:
One female receiving 2,4,4-trimethyl pentene at 1000 mg/kg bw/day was killed in extremis on Day 2 of lactation due to signs including under-active behaviour, hunched posture, piloerection, slow respiration, brown-coloured urine and brown perigenital staining. In the absence of any similar signs or findings in other females, it was considered that the death of this animal was incidental.
At 1000 mg/kg bw/day, animals showed transient salivation after dose administration. At 1000 mg/kg bw/day, a number of animals showed brown staining on the dorsal and ventral body surfaces, generally first observed in Week 4.

ORGAN WEIGHTS:
The absolute and bodyweight-relative weights of reproductive organs were similar in all groups and not affected by treatment. The absolute and bodyweight-relative weights of the liver and kidneys were high, when compared with the Controls, for females that received 1000 mg/kg bw/day.

GROSS PATHOLOGY:
After approximately six weeks of treatment (Day 4 of lactation for females), four females that received 1000 mg/kg/day had swollen livers or liver lobes. No remarkable findings were apparent at dosages up to 300 mg/kg bw/day.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Effect levels (fetuses)

Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Basis for effect level:
other: Developmental toxicity

Fetal abnormalities

Abnormalities:
no effects observed

Overall developmental toxicity

Developmental effects observed:
no

Applicant's summary and conclusion

Conclusions:
The reproductive/developmental no-observed-effect level (NOEL) was 1000 mg/kg bw/day.
Executive summary:

Groups of 10 males and 10 female CD rats were dosed orally with solutions of 2,4,4 -trimethylpentene in maize oil at dose levels of 0, 100, 300 or 1000 mg/kg/day in a combined reproductive toxicity / developmental toxicity screening test. Oral administration of 2,4,4 -trimethyl pentene at dosages of up to 1000 mg/kg bw/day was without adverse effect on the general condition or reproduction/developmental performance in female rats in this screening study, or on the growth and viability of their offspring up to Day 4 of age. The dosage of 1000 mg/kg bw/day was therefore considered to represent the no-observed-effect level (NOEL) for these reproductive parameters.