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Toxicological information

Toxicity to reproduction

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Administrative data

Endpoint:
screening for reproductive / developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 2005-04-26 to 2006-10-24
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report date:
2005

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Dodecamethylcyclohexasiloxane
EC Number:
208-762-8
EC Name:
Dodecamethylcyclohexasiloxane
Cas Number:
540-97-6
Molecular formula:
C12H36O6Si6
IUPAC Name:
dodecamethylcyclohexasiloxane

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Labs, Raleigh, NC, USA
- Age at study initiation: (P) 9 wks
- Weight at study initiation: (P) Males: 285-386 g; Females: 173-254 g
- Housing: 1/seuspended wire mesh cage
- Diet: standard diet ad libitum
- Water: drinking water ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 67.7-72.5 deg F (approximately 20 degrees celsius)
- Humidity (%): 35-59
- Air changes (per hr): 15.6
- Photoperiod (hrs dark / hrs light): 12 h/12 h

IN-LIFE DATES: From 2005-05-12 for 28 days (m) and 46 days (f) in the reproductive portion of this study.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:

Prepared for the whole study. Analysed (GC) 4 times to ensure homogeneity, stability and concentration.
Details on mating procedure:
- M/F ratio per cage: 1:1
- Length of cohabitation: 2 wk
- Proof of pregnancy: vaginal plug or sperm day 0 of pregnancy
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
GC analysis on 4 occasions to ensure homogeneity, stability and concentration.
Duration of treatment / exposure:
males: 28 days (including 14 days prior to mating)
females: 46 days (from 14 days prior to mating to postnatal day 3)
Frequency of treatment:
daily. 7 days/wk
Details on study schedule:
F1 not mated.
Doses / concentrationsopen allclose all
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
330 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale:
- Rationale for animal assignment (if not random): weight stratified randomization

Positive control:
None

Examinations

Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily. From day 20 after mating females were checked 3 times daily on weekdays for evidence of parturition.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

OTHER [reported fully under Repeated Dose]

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at sacrifice
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: yes
- How many animals: all toxicity groups

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at sacrifice
- Animals fasted: Yes / No / No data
- How many animals: all toxicity groups

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: FOB at start and completion
- Dose groups that were examined: males and toxicity group females
- Battery of functions tested: cage-side observations, hand-held observations, open field observations, categorical observations, hind and forelimb grip strength, landing foot splay, motor activity.

GROSS PATHOLOGY: Yes
all toxicity groups

HISTOPATHOLOGY: Yes
Microscopic examination of a relatively large range of tissues of all control and hi-dose group animals, and the lungs and thyroid of both sexes and liver of females at the low and mid doses. Examinations included testes, uterus, epididymides, ovaries and prostate.

ORGAN WEIGHTS
weights of a relatively large range of organs determined (including testes, uterus, epididymides, ovaries, prostate)


Oestrous cyclicity (parental animals):
No data
Sperm parameters (parental animals):
Parameters examined in males of the P generation: testis weight, epididymis weight, prostate weight.
Litter observations:
PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross abnormalities, weight gain (PND0-PND4)

GROSS EXAMINATION OF DEAD PUPS:
yes, for external abnormalities; possible cause of death was not determined for pups born or found dead
Postmortem examinations (parental animals):
SACRIFICE
- Male animals: after 2 wk mating
- Maternal animals: PND4

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera of all adults. For pregnant females the number of corpora lutea and implantation sites were recorded

HISTOPATHOLOGY / ORGAN WEIGHTS
Microscopic examination of a relatively large range of tissues of all control and hi-dose group animals, and the lungs and thyroid of both sexes and liver of females at the low and mid doses. Organ weights of a relatively large range of organs determined . The ovaries, uterus, testes, epididymides and prostate were included in organ weight determination and microscopic examinations.

Postmortem examinations (offspring):
SACRIFICE
- The F1 offspring were subjected to postmortem examinations (macroscopic) for external gross abnormalities

Statistics:
ANOVA (analysis of variance): body weights, organ weight, litter size, haematology, clinical chemistry etc
ANCOVA (analysis of covariance): FOB, reproductive prameters
Cochran-Armitage: microscopic findings
Reproductive indices:
mean gestation length
mean litter size
mean live litter size
mean litter weight
mean ratio of live births/litter size
mean implantation sites
mean corpora lutea
mean mating and fertility indices
Offspring viability indices:
vaible pups
average pup weight

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:
no effects observed
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
No effect on reproductive organs. [For effects on other organs see report of this study under repeated dose toxicity.]
Histopathological findings: neoplastic:
not specified
Other effects:
not examined

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
no effects observed

Effect levels (P0)

Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: No clear effects on reproductive toxicity in screening study

Target system / organ toxicity (P0)

Critical effects observed:
no

Results: F1 generation

General toxicity (F1)

Clinical signs:
not examined
Dermal irritation (if dermal study):
not examined
Mortality / viability:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Sexual maturation:
not examined
Anogenital distance (AGD):
not specified
Nipple retention in male pups:
not specified
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings:
not examined
Other effects:
no effects observed
Description (incidence and severity):
Gross pathology of the offspring - No treatment-related effects.

Developmental neurotoxicity (F1)

Behaviour (functional findings):
not specified

Developmental immunotoxicity (F1)

Developmental immunotoxicity:
not specified

Effect levels (F1)

Key result
Dose descriptor:
NOAEL
Generation:
F1
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects observed.

Target system / organ toxicity (F1)

Critical effects observed:
no

Overall reproductive toxicity

Reproductive effects observed:
no

Applicant's summary and conclusion

Conclusions:
A well reported oral combined repeated dose/reproductive and developmental toxicity study in the rat, conducted according to the current guideline and in accordance with GLP, identified an NOAEL of at least 1000 mg/kg bw/day for reproductive effects. This screening study found that the increased number of non-gravid females at this dose was not statistically significant. There was no evidence of this effect at the lower dose of 330 mg/kg bw/day.

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