Reaction Mass of 3,3-diphenylhexamethyltrisiloxane and 3,3,5,5-tetraphenylhexamethyltetrasiloxane

Toxicity to reproduction

Administrative data

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2004-09-14 to 2005-02-21

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

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)

Deviations:

yes

Remarks:

There is a discrepancy about treatment duration of females between executive summary and treatment regime paragraph. Also, the pups were killed on postnatal day 4.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane

EC Number:

222-222-9

EC Name:

1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane

Cas Number:

3390-61-2

Molecular formula:

C33H34O2Si3

IUPAC Name:

1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane

Test material form:

other: liquid

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 Laboratories Inc., United States
- Age at study initiation: 7 weeks
- Weight at study initiation:
Females: 189.8 to 237.2 g
Males: 285.5 to 357.1 g
- Fasting period before study: none
- Housing: individually housed individually in suspended wire-mesh cages during quarantine and throughout the course of the study.
- Diet: Certified rodent diet, ad libitum
- Water: Municipal water, ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 64-79°F
- Humidity (%): 30-70 %
- Air changes (per hour): 10-15/hour
- Photoperiod (hours dark / hours light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Dosing solutions were prepared twice during the course of the study. Corn oil was the chosen vehicle. The test substance was weighed then enough vehicle was added to obtain the correct volume.

VEHICLE
- Justification for use and choice of vehicle (if other than water): Corn oil was the chosen vehicle in the 14-day range-finding study.
- Concentration in vehicle: no data
- Amount of vehicle (if gavage): no data
- Lot/batch no. (if required): 1st preparation 122K0131; 2nd preparation 103K0107
- Purity: As provided by the manufacturer

Details on mating procedure:

- M/F ratio per cage: A 1:1 mating ratio was used.
- Length of cohabitation: The female animals were housed continuously with the same male until evidence of mating occurred.
- Proof of pregnancy: presence of a vaginal plug and/or sperm in vaginal smear referred to as day 0 of pregnancy
- After successful mating each pregnant female was caged: individually
- Any other deviations from standard protocol: no

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Dosing solutions analysis were analysed by CG/FID to verify concentration, stability and homogeneity of the test substance in the vehicle. Prior to the experiment, a high dose solution was prepared and stability testing was performed on days 0, 14, 35 and 50. Following the second preparation of dose solutions, homogeneity analysis of the low and high dose solutions was conducted on day 0 and stability analysis of the low dose solution was conducted on days 0 and 50. Concentration verification was of the dose solutions was conducted on the day of the first preparation and prior to the end of dosing.

Duration of treatment / exposure:

Both males and females were treated with the test substance for 2 weeks prior to mating period and continued through the mating period. Males were treated for 92 days and females were treated up to and including postpartum day 3 according to treatment regime paragraph in the study report or up to gestation day 19 according to the execute summary in the study report.

Frequency of treatment:

Daily, 7 days a week

Details on study schedule:

- parental animals not mated until 2 weeks after selection.
- Age at mating of the mated animals in the study: 9 weeks

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

Doses / concentrations 4

Dose / conc.:

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

No. of animals per sex per dose:

10 males and 10 females per dose

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: Dose levels were determined based on the results of a 14-day range-finding study. Doses were administered at a volume of 2 mL/kg of body weighed. The administered volumes were based on the weekly scheduled body weights.

Positive control:

Not used

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: prior to start of treatment and on week 12 of the treatment period.
- Cage side observations included: abnormal muscle movements (tremors, convulsions), abnormal behaviour, posture and resistance to removal.

DETAILED CLINICAL OBSERVATIONS: Yes. The general health conditions of the animals were recorded. Detailed physical examinations included changes in skin, fur, eyes, mucous membranes, occurrence of secretions and excretions, and autonomic activity. Changes in gait, posture, and response to handling as well as the presence of clonic or tonic movements, stereotypes, bizarre behaviour were also recorded.
- Time schedule: once a day for general observations; detailed observations were performed before the first dose and once a week thereafter

BODY WEIGHT: Yes
- Time schedule for examinations: on the first day of dosing, then once a week and on the day of necropsy. During gestation the females were weighed on gestation days 0, 7, 14 and 20, within 24 hours after parturition, and day 4 postpartum.

OTHER:
FOOD CONSUMPTION: Yes
- Time schedule for examination: Individual food consumption for male animals was recorded on the first day of dosing, weekly thereafter until the day of necropsy with an exception of the two week mating period. Female animals' food consumption was recorded on days 1, 8, 15, and on gestation days 0, 7, 14 and 20, and on day 4 postpartum.

Oestrous cyclicity (parental animals):

Not examined.

Sperm parameters (parental animals):

Parameters examined in adult control and high dose males: 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, presence of gross anomalies, weight gain

GROSS EXAMINATION OF DEAD PUPS: yes, for external abnormalities only

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals were sacrificed at the end of the treatment period.
- Maternal animals: All surviving female animals were euthanized on postpartum day 4. The females that did not deliver were euthanized on gestation day 25 or 26.

GROSS NECROPSY
- Gross necropsy consisted of examination of the external surface and all orifices of the body, the cranial, thoracic and abdominal cavities and their contents in male animals. For pregnant females, the number of corpora lutea and the number of implantation sites were recorded. For 8 females with positive evidence of mating that failed to produce litter, the uteri were stained to enable counting of possible reabsorbed implant sites.

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in Table [No.1] were prepared for microscopic examination and weighed, respectively.

Postmortem examinations (offspring):

SACRIFICE
- The F1 offspring were sacrificed at 4 days of age.
- These animals were subjected to postmortem macroscopic examinations only.
GROSS NECROPSY
- Gross necropsy consisted of external examinations.

HISTOPATHOLOGY / ORGAN WEIGTHS
No pup tissues were collected.

Statistics:

ANCOVA (Analysis of Covariance): used for analysis of reproductive parameters
ANOVA: used for analysis of litter size

Reproductive indices:

The evaluated reproductive indices were: mean gestation length, mean number of implantation sites, mean number of corpora lutea, mean mating and fertility indices

Offspring viability indices:

The evaluated offspring viability indices were: mean litter size, mean live litter size, mean litter weight, mean ration live births/ litter size

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Details on results (P0)

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS): No clinical signs or mortality were noted among male and female animals.

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS): No statistically significant differences among male exposure groups were noted. The female reproductive groups showed statistically significant differences in body weights for gestation week 2. The observed changes were not considered toxicologically significant. There were no statistically significant changes in the average daily food consumption.

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS): There were no treatment-related effects apparent for any of the reproductive endpoints. Three females in 0 and 500 mg/kg/day groups had positive evidence of mating and were non-pregnant. One female in 100 mg/kg/day had positive evidence on mating and was non-pregnant. One female in 1000 mg/kg/day group was found with one past term foetus at necropsy.

ORGAN WEIGHTS (PARENTAL ANIMALS): There were no statistically significant changes in organ weights in male animals.

GROSS PATHOLOGY (PARENTAL ANIMALS): There were no gross morphological changes noted in test animals.

HISTOPATHOLOGY (PARENTAL ANIMALS): There were no histopathological changes noted in male animals (male animals examined only).

Effect levels (P0)

Key result

Dose descriptor:

NOAEL

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

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings:

not examined

Details on results (F1)

VIABILITY (OFFSPRING): No test-substance induced effect was observed.

CLINICAL SIGNS (OFFSPRING): No test-substance induced effect was observed.

BODY WEIGHT (OFFSPRING): No test-substance induced effect was observed.

GROSS PATHOLOGY (OFFSPRING): No test-substance induced effect was observed.

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

Overall reproductive toxicity

Key result

Reproductive effects observed:

no

Any other information on results incl. tables

Table 1: Mean reproductive parameters for reproductive group female rats

		Litter						Initial		Final
	Days gestation	Male pups	Female pups	Males/females	Total pups	Day 4 viable pups	Viable/ total	Litter weight (g)	Average pup weight (g)	Litter weight (g)	Average pup weight (g)	Total implants	Corpora lutea
Group 1	Control
Mean	22	8.4	7.9	1.1	16.3	15.4	0.9	108.9	6.7	160.5	10.5	17.0	22.6
N	7A	7	7	7	7	7	7	7	7	7	7	7	7
Group 2	200 mg/kg bw/day
Mean	21.9	7.0	8.1	0.9	15.1	14.7	1.0	95.6	6.3	150.2	10.3	16.6	21.3
N	9A	9	9	9	9	9	9	9		9	9	9	9
Group 3	500 mg/kg bw/day
Mean	21.7	6.1	9.6	0.7	15.7	15.3	1.0	99.9	6.4	152.7	10.0	16.4	18.0
N	7A	7	7	7	7	7	7	7	7	7	7	7	7
Group 4	1000 mg/kg bw/day
Mean	21.8	6.9	8.8	0.9	15.7	15.1	1.0	98.9	6.3	147.2	9.8	16.6	20.9
N	9B	9	9	9	9	9	9	9	9	9	9	9	9

A: data of non-pregnant females with positive evidence of mating not included in calculations

B: data of female that failed to deliver not included in calculations

Table 2: Summary of reproductive performance for reproductive group female rats

	Group 1 (control)	Group 2 (200 mg/kg bw/day)	Group 3 (500 mg/kg bw/day)	Group 4 (1000 mg/kg bw/day)
Females on study	10	10	10	10
Females that died during study	0	0	0	0
Females euthanized in extremis	0	0	0	0
Females allowed to deliver	10	10	10	10
Nongravid	3	1	3	0
Gravid	7	9	7	10
Females with evidence of copulation	10	10	10	10
Number which delivered	7	9	7	9
Number which did not deliver	3	1	3	1
Females with no evidence of copulation	0	0	0	0
Number which delivered	0	0	0	0
Number which did not deliver	0	0	0	0

Applicant's summary and conclusion

Conclusions:

In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test in rats for 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane, the reported NOAEL value for P and F1 was >= 1000 mg/kg/day.