1,1,1,3,5,5,5-heptamethyl-3-octyltrisiloxane

Toxicity to reproduction

Administrative data

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

7 April 2016 to 21 July 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

1996

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

1995

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3550, Reproduction/Developmental Toxicity Screening Test

Version / remarks:

2000

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3050, Repeated dose 28-day oral toxicity study in rodents

Version / remarks:

2000

Deviations:

no

Test guideline 5

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity in Rodents)

Version / remarks:

2008

Deviations:

no

Test guideline 6

Qualifier:

according to guideline

Guideline:

other: EU Method B.7 (Repeated Dose (28 Days) Toxicity (Oral))

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,1,1,3,5,5,5-heptamethyl-3-octyltrisiloxane

EC Number:

241-881-3

EC Name:

1,1,1,3,5,5,5-heptamethyl-3-octyltrisiloxane

Cas Number:

17955-88-3

Molecular formula:

C15H38O2Si3

IUPAC Name:

2,2,4,6,6-pentamethyl-4-octyl-3,5-dioxa-2,4,6-trisilaheptane

Test material form:

liquid

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Expiration date of the lot/batch: 04 June 2017
- Purity test date: no data
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: In refrigerator (2-8°C)
- Stability under test conditions: stable
- Solubility and stability of the test substance in the solvent/vehicle: Predicted solubility = 2.8E-05 mg/L at
20°C
TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Formulations (w/w) were prepared daily within 6 hours prior to dosing and were homogenized to a visually acceptable level. Adjustment was made for specific gravity of the vehicle and test substance.
- Preliminary purification step (if any): No correction was made for the purity/composition of the test item.

FORM AS APPLIED IN THE TEST: diluted in corn oil

Test animals

Species:

rat

Strain:

other: Crl:WI(Han)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Deutschland, Sulzfeld, Germany
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation: 10 weeks males and 11 weeks females
- Weight at study initiation: all animals within ± 20% of the sex mean
- Fasting period before study: none
- Housing: During pre-mating the animals were housed in groups of 5 animals/sex/cage in Macrolon plastic cages. During mating main group females were caged together with main group males on a one to-one-basis in Macrolon plastic cages. During post-mating period main males were housed in their home cage with a maximum of 5 animals/cage; main group females were individually housed in Macrolon plastic cages.
- Diet: pelleted rodent diet, ad libitum
- Water: tap water, ad libitum
- Acclimation period: 5 days

DETAILS OF FOOD AND WATER QUALITY: Diet, water, bedding and cage-enrichment/nesting material
evaluation for contaminants and/or nutrients was performed according to facility standard procedures.
There were no findings that could interfere with the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 - 24°C
- Humidity (%): 40 - 70%
- Air changes (per hr): 10/ hour
- Photoperiod (hrs dark / hrs light): 12/ 12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:Formulations (w/w) were prepared daily within 6 hours prior to dosing and were homogenized to a visually acceptable level. Adjustment was made for specific gravity of the vehicle and test substance. No correction was made for the purity/composition of the test item.
VEHICLE
- Justification for use and choice of vehicle (if other than water): corn oil was the selected vehicle

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: A maximum of 14 days was allowed for mating.
- Proof of pregnancy: vaginal plug or sperm in vaginal smear referred to as day 0 of pregnancy
- Further matings after two unsuccessful attempts: no
- After successful mating each pregnant female was caged (how): females were individually housed in Macrolon plastic cages
- Any other deviations from standard protocol: none

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses were conducted during the treatment phase in Week 1 and Week 6, according to a validated method. Samples of formulations were analysed for homogeneity (highest and lowest concentration) and accuracy of preparation (all concentrations).

Duration of treatment / exposure:

Main and recovery males: 29 days
Main females: 41 to 47 days
Recovery females: 43 days

Frequency of treatment:

Once daily for 7 days per week

Details on study schedule:

- Age at mating of the mated animals in the study: 10 - 11 weeks

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

100 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

300 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

Main group: 10 males and 10 females
Recovery group: 5 males and 5 females (control and high dose)

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: Based on toxicity results of a 14-day dose range finding study.
- Rationale for animal assignment (if not random): The animals were assigned randomly.
- Section schedule rationale (if not random): random

Positive control:

Not used

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at lest once daily for clinical signs and twice daily for mortality and viability
- Cage side observations checked included: clinical signs of toxicity, mortality, viability

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once prior to start of treatment and at weekly intervals during the treatment period this was also performed outside the home cage in a standard arena.

BODY WEIGHT: Yes
- Time schedule for examinations: Males and females were weighed on the first day of exposure (prior to first exposure) and weekly thereafter. Mated Main females were weighed on Days 0, 4, 7, 11, 14, 17 and 20 postcoitum and during lactation on Days 1 and 4.

Oestrous cyclicity (parental animals):

Not examined

Sperm parameters (parental animals):

Parameters examined in P1 male parental generations: testis weight, epididymis weight

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: no


PARAMETERS EXAMINED
The following parameters were examined in F1 offspring: number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities

GROSS EXAMINATION OF DEAD PUPS: yes, for external and internal abnormalities

ASSESSMENT OF DEVELOPMENTAL NEUROTOXICITY: No

ASSESSMENT OF DEVELOPMENTAL IMMUNOTOXICITY: No

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals were sacrificed following completion of the mating period (a minimum of 28 days of dose administration)
- Maternal animals: All surviving animals were sacrificed on lactation Days 5-7

GROSS NECROPSY
- Gross necropsy included: See table 1

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in Table [2] were prepared for microscopic examination and weighed, respectively.

Postmortem examinations (offspring):

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera

HISTOPATHOLOGY / ORGAN WEIGTHS
Histopathological examination of pups was not performed.

Statistics:

• If the variables could be assumed to follow a normal distribution, the Dunnett-test based on a pooled variance estimate was applied for the comparison of the treated groups and the control groups for each sex.
• The Steel-test was applied if the data could not be assumed to follow a normal distribution.
• The Fisher Exact-test was applied to frequency data.
• The Kruskal-Wallis nonparametric ANOVA test was applied to motor activitydata to determine intergroup differences.

Reproductive indices:

Mating index (%), Fertility index (%), Conception index (%), Gestation index (%), Duration of gestation (%)

Offspring viability indices:

Percentage live males at First Litter Check, Percentage live females at First Litter Check, Percentage of postnatal loss,Viability index.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Description (incidence and severity):

No clinical signs or abnormalities during weekly arena observations were noted during the observation period that were considered to be related to treatment.
Any clinical signs noted during the treatment period occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study and did not show any apparent dose-related trend. At the incidence observed, these were considered to be unrelated to treatment.

Mortality:

no mortality observed

Description (incidence):

No mortality occurred during the study period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

No toxicologically relevant changes in body weight were noted.

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

At 1000 mg/kg, an elongated mean activated partial thromboplastin time (APTT) was recorded for males at the end of treatment. The mean remained within the range considered normal for rats of this age and strain and at the end of the recovery period, mean activated partial thromboplastin time was similar to controls. The statistically significant lower red blood cell counts and haematocrit of females at 300 mg/kg at the end of treatment occurred in the absence of a dose-related trend. As such this was considered to be unrelated to treatment.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No toxicologically relevant changes occurred in clinical biochemistry parameters of treated rats.

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

No toxicologically relevant effects on hearing ability, pupillary reflex, static righting reflex and grip strength were observed in selected animals. Motor activity was similar between treated and control groups. All groups showed a similar motor activity habituation profile with a decreasing trend in activity over the duration of the test period. One male at 100 mg/kg (no. 18) had an absent pupillary reflex of the right eye and had a white stain on the eye. Given the incidental nature of this finding, this was considered unrelated to treatment with the test item.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

There were no test item-related microscopic observations. Slight vacuolation in the zona fasiculata of the adrenal glands was recorded in 1 male of the 100 mg/kg/day main group and 1 male of the 1000 mg/ kg/day main group and in 2 males of the 1000 mg/kg/day recovery group. Based on the absence of a clear dose-relationship and the fact that slight vacuolation in the zona fasciculata can be observed as a background finding in control rats (although this was not the case in the present study), the adrenal gland finding is not considered to be test item related.

Histopathological findings: neoplastic:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Description (incidence and severity):

The mating index was not affected by treatment. All females showed evidence of mating. Fertility and conception indices were not affected by treatment. All mated females became
pregnant. Precoital time was not considered to be affected by treatment. Number of corpora lutea and implantation sites was not considered to be affected by treatment. For females 73 and 85, the number of pups was slightly higher than the number of implantations and/or corpora lutea. This was considered to have been caused by normal resorption of these
areas as these enumerations were performed on Day 5 of lactation.

Effect levels (P0)

Key result

Dose descriptor:

NOAEC

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 (P0)

Critical effects observed:

no

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Description (incidence and severity):

No clinical signs occurred among pups that were considered to be related to treatment.

Mortality / viability:

no mortality observed

Description (incidence and severity):

No mortality occurred among pups that was considered to be related to treatment with the test item.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

No effects on body weight was observed among pups.

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Description (incidence and severity):

No macroscopic findings were noted.

Histopathological findings:

not examined

Developmental neurotoxicity (F1)

Behaviour (functional findings):

not examined

Developmental immunotoxicity (F1)

Developmental immunotoxicity:

not examined

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:

In the combined 28-day repeated dose toxicity study with the reproduction/ developmental toxicity screening test, the reported NOAEL for reproductive and developmental effects was greater than 1000 mg/kg bw. No treatment-related changes were observed in any of the test animals.