Reaction mass of 1,1,1,5,5,5-hexamethyl-3-phenyl-3-((trimethylsilyl)oxy)trisiloxane and 1,1,1,7,7,7-hexamethyl-3,5-diphenyl-3,5-bis[(trimethylsilyl)oxy]tetrasiloxane and 1,1,1,9,9,9-hexamethyl-3,5,7-triphenyl-3,5,7-tris((trimethylsilyl)oxy)pentasiloxane

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 January 1996 to 25 July 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

temperature 20-26°C and humidity 27-73% (19-25°C and 30-70% recommended), guideline recommends treatment until the day before caesarean section

Principles of method if other than guideline:

A developmental toxicity study to investigate the effects of oral gavage treatment during days 6 to 15 of gestation on pregnant rats and their foetuses, as evaluated on gestation day 20.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: deleted from report
- Age at study initiation: about 10-12 weeks
- Weight at study initiation: approximately 220 g
- Fasting period before study: no data
- Housing: singly in suspended polycarbonate cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): municipal water ad libitum
- Acclimation period: approximately 2 weeks (prior to mating)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 26
- Humidity (%): 27 to 73
- Air changes (per hr): minimum of 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 11 April 1996 To: 13-17 May 1996

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Dose formulations of 10, 100 and 200 mg/ml were prepared by weighing out an appropriate amount of Dow Corning(R) 556 Cosmetic Grade Fluid into a calibrated Erlenmeyer flask and bringing it to volume with corn oil. The formulations were heated until warm while stirring, with stirring continuing for at least half an hour. Solutions were prepared on 29 April and 6 May 1996, and stored at room temperature (with stirring prior to dispensation into dosing vials and during dosing).

VEHICLE
- Justification for use and choice of vehicle (if other than water): no data
- Concentration in vehicle: 10, 100 or 200 mg/ml
- Amount of vehicle (if gavage): 5 ml/kg bw
- Lot/batch no. (if required): no data
- Purity: no data

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of the dosing formulations were sent to the Sponsor for confirmation of test material concentration. Stability and homogeneity were also determined by the Sponsor.

Details on mating procedure:

- Impregnation procedure: cohoused
- M/F ratio per cage: 1:1 or 1:2
- Length of cohabitation: no data
- Further matings after two unsuccessful attempts: no data
- Verification of same strain and source of both sexes: no data
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

10 days (gestation days 6 through 15)

Frequency of treatment:

daily

Duration of test:

15 days (untreated on days 0-5 of gestation, treated from days 6 to 15 of gestation, sacrifice at day 20 of gestation)

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

50 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

500 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

1 000 mg/kg bw/day

No. of animals per sex per dose:

25 females

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: range-finding study

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily on weekdays and once daily on weekends for morbidity/mortality. Animals were observed for signs of toxicity once daily 0-3 hours after dose administration, and once daily on non-dosing days.
- No data on which specific cage side observations were performed

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: physical examinations on gestation days 0 and 20

BODY WEIGHT: Yes
- Time schedule for examinations: dams weighed on gestation days 0, 6, 11, 16 and 20

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes (gestation days 0-6, 6-11, 11-16 and 16-20)
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #20
- Organs examined: uterus, ovaries, liver

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

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: all per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: half per litter
See "Any other information on materials and methods incl. tables" for details on foetal examinations.

Statistics:

Means and standard deviations were calculated for all measured parameters.
ANOVA (analysis of variance) was used to evaluate dam body weight, body weight gain, food consumption, uterus weight, liver weight, corrected body weight, corrected body weight gain, and foetal weight.
Analyses were performed using LABCAT (IPA, Inc. Princeton, N.J., version 4.64) for dam body weight, body weight gain, and food consumption; and Systat (SPSS, Inc., Chicago, IL, version 5.0) for uterus weight, liver weight, corrected body weight, corrected body weight gain, and foetal weights.
A one-factor ANOVA was used for viability data on corpora lutea, total implants, live implants, non-live implants (resorptions and deaths), the percent live implants, the percent non-live (resorptions and death) implants and percent preimplantation loss.
Dunnett's test was used for post-hoc comparisons between treatment and control groups in the presence of significant main effects.
Skeletal, visceral, cephalic, and gross external malformation data were statistically analysed by Chi-square or Fisher Exact tests when the incidence in the treated groups was higher than controls (i.e. difference in absolute number of affected fetuses of 3 or greater).
A minimum significance level of p ≤ 0.05 was used in the comparisons.

Indices:

female:male ratio

Historical control data:

no data

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects
Details on maternal toxic effects:
No clinical signs of maternal toxicity were evident during the study, or were apparent from gross necropsy observations. Mean body weights, body weight gains, food consumption, uterus weights and liver weights showed no test article-related effects. No significant adverse findings were noted following Caesarean section (see table 1).

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

other: overall effects - no adverse effects on dams at any dose

Maternal abnormalities

Abnormalities:

no effects observed

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
Statistically significant increases in foetal body weights for the low dose group compared to vehicles for males (mean 4.29 vs 4.07 g) and combined sexes (mean 4.20 vs 3.99 g) were not considered biologically significant.
Visceral and skeletal abnormalities observed (see tables 2 and 3) were low in incidence, sporadic and not considered to be related to treatment as there was no dose response relationship, and a similar incidences of most of the abnormalities occurred in the control group.

Effect levels (fetuses)

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: overall effects - no adverse effects on foetuses at any dose

Fetal abnormalities

Abnormalities:

no effects observed

Overall developmental toxicity

Developmental effects observed:

no

Any other information on results incl. tables

Table 1: Caesarean Section Observations

Observation	Dose (mg/kg bw/day)
	0	50	500	1000
# Animals Assigned (Mated)	25	25	25	25
# Animals Pregnant Pregnancy Rate (%)	23 92%	22 88%	22 88%	23 92%
Maternal Wastage # Died # Died Pregnant # Died Nonpregnant # Aborted # Premature Delivery	0 0 0 0 0	0 0 0 0 0	0 0 0 0 0	0 0 0 1 0
Total # Corpora Lutea (Mean Corpora Lutea/Dam)	312 (13.57 ± 2.61)	247 (11.23 ± 3.07)	267 (12.14 ± 3.56)	267 (12.71 ± 1.76)
Total # Implantations (Mean Implantations/Dam)	294 (12.78 ± 3.67)	229 (10.41 ± 3.61)	253 (11.5 ± 3.71)	271 (11.78 ± 3.1)
Total # Litters	23	22	22	22
Total # Live Male Foetuses (Mean Live Foetuses/Dam)	139 (6.04 ± 1.99)	115 (5.23 ± 2.65)	129 (5.86 ± 3)	135 (6.14 ± 1.75)
Total # Live Female Foetuses (Mean Live Foetuses/Dam)	143 (6.22 ± 2.7)	106 (4.82 ± 1.87)	119 (5.41 ± 2.63)	130 (5.91 ± 1.95)
Total # Resorptions (Mean Resorptions/Dam)	12 (0.52 ± 0.79)	8 (0.36 ± 0.79)	5 (0.23 ± 0.43)	6 (0.26 ± 0.45)
Sex Ratio (% Male)	50%	52%	52%	50%
Preimplantation Loss (%)	7.83 ± 17.71	8.84 ± 13.54	6.63 ± 11.94	4.13 ± 8.16

 

Table 2: Visceral Examinations

Observations^+	Dose (mg/kg bw/day)
	0	50	500	1000
#Fetuses (litters) examined	282 (23)	221 (22)	248 (22)	252 (21^b)
#Fetuses (litters) affected	3 (3)	3 (2)	5 (2)	7 (6)
Hydroureter	0 (0)^a	0 (0)	1 (1)	1 (1)
Hydronephrosis	0 (0)	1 (1)	0 (0)	0 (0)
Hyroureter/hydronephrosis Slight/mild Moderate/severe	3 (3) 3 (3) 0 (0)	2 (2) 3 (2) 0 (0)	2 (2) 1 (1) 2 (2)	4 (3) 5 (4) 0 (0)
Heart, minor vessel defect	0 (0)	0 (0)	4 (1)	1 (1)
Lung, lobe missing	0 (0)	0 (0)	0 (0)	1 (1)

⁺Some observations may be grouped together

^aFetal (litter) incidence

^bData for all foetuses from one dam not included due to premature fixation in 70% ethanol

 

Table 3: Skeletal Examinations

Observations^+	Dose (mg/kg bw/day)
	0	50	500	1000
# Fetuses (litters) examined	140 (23)	110 (22)	120 (22)	134 (22)
Sternebrae Any variation % Affected Malformations % Affected	17 (9)^a 12.1(39.1) 0 (0) 0 (0)	8 (4) 7.3 (18.2) 0 (0) 0 (0)	11 (8)  9.2 (36.4) 1 (1) 0.8 (4.5)	3 (2)  2.2 (9.1) 0 (0) 0 (0)
Centrae Any variation % Affected	27 (13) 19.3(56.5)	22 (13) 20 (59.1)	31 (15) 25.8(68.2)	22 (12) 16.4(54.5)
Skull Any variation % Affected	13 (6) 9.3 (26.1)	10 (5) 9.1 (22.7)	15 (8) 12.5(36.4)	14 (6) 10.4(27.3)
Body of Hyoid Any variation % Affected	0 (0) 0 (0)	0 (0) 0 (0)	0 (0) 0 (0)	0 (0) 0 (0)
Ribs Wavy/bulbous 13^thrib, any variation Rudimentary 14^th Supernumary14^th Cervical rib All rib abnormalities % Affected	0 (0) 4 (2) 13 (7) 0 (0) 1 (1) 18 (9) 12.9 (39.1)	2 (2) 0 (0) 7 (7) 0 (0) 6 (3) 15 (10) 13.6(45.5)	1 (1) 0 (0) 8 (5) 0 (0) 3 (2) 12 (7) 10 (31.8)	0 (0) 11 (5) 9 (6) 0 (0) 3 (3) 21 (12) 15.7(54.5)
Pelvic girdle Pubis reduced % Affected	1 (1) 0.7 (4.3)	0 (0) 0 (0)	0 (0) 0 (0)	0 (0) 0 (0)
Vertebral column Lumnar vertebrae Any variation % Affected Sacral vertebrae Incomplete ossification % Affected	0 (0) 0 (0)   2 (2) 1.4 (8.7)	0 (0) 0 (0)   1 (1) 0.9 (4.5)	0 (0) 0 (0)   1 (1) 0.8 (4.5)	0 (0) 0 (0)   0 (0) 0 (0)

⁺Some observations may be grouped together

^aFetal(litter) incidence

Applicant's summary and conclusion

Conclusions:

In a developmental toxicity study, with a protocol similar to that decribed by OECD Test Guideline 414 and performed to GLP, no significant adverse effects were noted in the foetuses of pregnant rats treated orally with Dow Corning(R) 556 Cosmetic Grade Fluid at up to 1000 mg/kg bw/day from days 6 to 15 of gestation. Under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for developmental toxicity and maternal toxicity was 1000 mg/kg bw/day (the highest dose tested).

Executive summary:

In a GLP-compliant study, with a protocol similar to that described by OECD Test Guideline 414, Dow Corning Corporation^® 556 Cosmetic Grade Fluid was tested for its potential developmental toxicity to Sprague-Dawley rats following oral administration.

 

Male and female rats were mated, with sperm-positive vaginal smears were taken as day 0 of gestation. Females were housed separately during gestation. Groups of 25 sperm-positive females were treated by daily gavage administration with the test material at 0, 50, 500 or 1000 mg/kg bw (in corn oil) on days 6 to 15 of gestation. Sacrifice and caesarean section took place on day 20 of gestation and a comprehensive range of developmental parameters were assessed. From each dam, the uterus and ovaries were removed and analysed and the liver was also removed and weighed. Foetuses were subject to necropsy to detect any gross macroscopic abnormalities.

 

All dams survived throughout the course of the study. Over the course of the study, there were no signs of maternal toxicity and gross necropsy of the dams did not reveal any significant adverse effects. Mean body weights, body weight gains, food consumption, uterus weights and liver weights showed no treatment-related effects. In the foetuses, there were no biologically significant differences in body weights. No statistically significant increases in foetal deaths, resorptions or malformations were observed in treatment-group foetuses relative to controls.

 

Under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for developmental toxicity and maternal toxicity was 1000 mg/kg bw/day (the highest dose tested).