2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10 days (days 6 to 15 of gestation)

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane

EC Number:

222-217-1

EC Name:

2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane

Cas Number:

3388-04-3

Molecular formula:

C11H22O4Si

IUPAC Name:

trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane

Details on test material:

- Name of test material (as cited in study report): β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane
- Substance type: Organosilane
- Physical state: Liquid

Test animals

Species:

rat

Strain:

Fischer 344

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories
- Age at study initiation: 53 days and 70 days for females and males, respectively (when received from breeders).
- Weight at study initiation: not less than 150 or 200g for females and males, respectively (when received from breeders).
- Fasting period before study: No data
- Housing: Stainless steel wire mesh cages
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum):Ad libitum
- Acclimation period: Two weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): No data
- Humidity (%): No data
- Air changes (per hr): No data
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: No data

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Dosing solutions were prepared once before the dosing period and aliquots were analysed before and after the dosing period. A dose volume of 10ml/kg bw was employed with the volume being based on the gestation day six body weight of each animal. The four concentrations were 0.0, 2.5, 10.0 or 25.0% (w/w) in corn oil.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analysis was done using a gas chromatographic procedure emplying a thermal conductivity detector calibrated with appropriate standards in corn oil. The analysis of dosing formulations indicated that they were all within 96.9-106.4% of the target with no losses over the dosing period.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: Until plug-positive
- Verification of same strain and source of both sexes: [yes / no (explain)] no data
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy.

Duration of treatment / exposure:

Days six to 15 of pregnancy.

Frequency of treatment:

Daily

Duration of test:

Ten days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0.25 other: ml/kg

Doses / concentrations 2

Dose / conc.:

1 other: ml/kg

Doses / concentrations 3

Dose / conc.:

2.5 other: ml/kg

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on the results of a dose range-finding study.
- Rationale for animal assignment (if not random): Random

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily


BODY WEIGHT: Yes
- Time schedule for examinations: Gestational days 0, 6, 12, 15, 18 and 21


FOOD CONSUMPTION: Yes
- Food consumption for each animal determined g food/kg body weight/day: Yes, for gestational 3-day intervals 0-3, 3-6, 6-9, 9-12, 12-15, 15-18 and 18-21


WATER CONSUMPTION: No data



POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: Liver, kidney, uterus, ovaries, oviducts, uterus (all weighed and examined)

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 live and dead fetuses were weighed and examined for external variations and malformations including cleft palate.
- Soft tissue examinations: Yes: half of live fetuses in each litter examined for thoracic and abdominal visceral abnormalities.
- Skeletal examinations: Yes: half of each litter was examined for skeletal variations and malformations.
- Head examinations: Yes: animals that were used for soft tissue examinations were decapitated for examination of craniofacial structures.

Statistics:

The unit of comparison was the pregnant female or the litter. Results of the quantitative continuous variables (e.g. maternal body weight, organ weights and fetal weights) were intercompared for the three treatment groups and the control group using Levene's test for equal variances, analysis of variance (ANOVA), and t-test with Bonferroni probabilities. When Levene's test indicated homogenous variances and the ANOVA was significant, the pooled t-test was used for pairwise comparisons. When Levene's test indicated heterogeneous variances, all groups were compared by an ANOVA for unequal variances followed, when necessary, by the separate variance t-test for pairwise comparisons. Non-parametric data obtained following laparohysterectomy were statistically evaluated using the Kruskal-Wallis test when appropriate. Frequency data were compared using Ficher's exact test. For all statistical tests the fiducial limit of 0.05 (two-tailed) was used as the critical level of significance.

Indices:

The indices presented in the reference were: percentage pregnant at termination, corpora lutea per dam, total implants per litter, percentage preimplantation loss, live fetuses per litter, nonviable implants per litter, early resorption, late resorption, dead fetuses, percentage live fetuses per litter, sex ratio, fetal body weight per litter (male, female and total).

Historical control data:

No historical data provided.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
the evaluation of gestational parameters is summarised in Table 2. All dams survived to their scheduled termination day. There were no abortions, no early deliveries, and no animals were removed from the study. Although not statistically significant, there was a dose-related trend towards decreased body weight on gestation days 12, 15 an 18. There were significant decreases in body weight gain for the dams from the high dose group (2.5ml/kg) on gestational days 6-12, 6-15, and 6-18. The dams from the middle dose group (1.0ml/kg) had lower body weight gains than the control group but the differences were not statistically significant. At termination on gestational day 21, there was no significant difference in maternal body weights across all groups. Rat maternal food consumption, expressed as g/dam/day, was similar across all groups in the pre- and postdosing periods. There was a significant decrease in food consumption on gestational days 6-9 at 2.5 ml/kg but no other biologically or statistically significant change in maternal food consumption was present. The clinical observations of treated dams indicated behavioural and central nervous system effects (co-ordination loss, lethargy, facial twitching, whole-body twitching, prone positioning on the cage floor) in the high dose group, and facial twitching in the mid dose group for a small number of animals at each dose and only during the treatment period. None of these effects were observed in the low dose or control groups. There was a clear dose-related incidence of urogenital area wetness, which seemed to resolve in all but a few of the high level animals shortly after the treatment period was over. Piloerection was noticed in two high dose animals, and laboured or audible respiration was present in a few high dose animals and one intermediate dose animal during the treatment period. A dose-related incidence of lacrimation, perinasal wetness, red fluid at the vaginal orifice, and perioral wetness or encrustation was also present. Other clinical signs, both during gestation and treatment and at scheduled termination (e.g. alopecia, pale liver, kidney cyst) were not treatment-related. At scheduled sacrifice there was a significant decrease in corrected body weight (body weight at termination minus gravid uterine weight) at the high dose relative to the value in controls. There was an increase in relative liver weight which was statistically significant in the high dose group versus the controls. Gravid uterine weight, absolute liver, and kidney weights and relative kidney weights were unaffected by treatment.
Evaluation of gestational parameters for the rats indicated no treatment-related effects on number of ovarian corpora lutea of pregnancy, total implantations, viable or nonviable implantations per litter, percentage preimplantation loss, percentage live fetuses per litter, sex ratio (% males), male and female fetal body weights, or mean litter weights.

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

>= 0.25 other: ml/kg

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
The type and frequency of fetal malformations and significant variations are summarised in Tables 3 and 4. There was no significant increase in the number of litters with one or more affected fetuses in any treatment group relative to the control group for individual malformations or for total external, visceral (including cranofacial), and skeletal malformations, or for total malformations (all categories combined). There were no treatment-related changes in the incidence of any external variations in the rat study out of seven observed. There was a significant increase in the incidence of dilation of the lateral cerebral ventricles (a visceral variation) at the high dose, although a clear dose-response was not evident. This variation might be indicative of fetal toxicity. No other statistically significant or treatment-related changes in the incidence of visceral variations were noted in any of the dose groups out of 31 findings. There was only one possible treatment-related change in the incidence of skeletal variations out of 93 variations observed. This was a significant increase in the incidence of poorly ossified proximal phalanges of the forelimbs at 2.5 ml/kg. The incidence of four additional skeletal findings in treated groups differed significantly from that of controls, but these were not treatment-related based on the lack of a dose-response relationship.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

>= 2.5 other: ml/kg

Based on:

test mat.

Basis for effect level:

other: embryotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Table 1: Mean maternal Body Weight Gain (±SD)a

Interval	Dose in ml/kg
	Control (22)	0.25 (21)	1.0 (21)	2.5 (23)
Pretreatment: Days 0-6	14.4 (4.6)	13.8 (3.3)	13.7 (3.9)	14.1 (3.2)
Treatment: Days 6-15	23.4 (4.9)	23.0 (5.5)	20.8 (5.6)	17.7 (3.5)**
Posttreatment: Days 15-21	44.7 (9.7)	45.6 (8.1)	44.4 (6.0)	47.4 (6.4)

^{a  Data} extracted from pg 443 of the study report

*  Significantly different (p 0.05) from the control>0.05)

** Significantly different (p 0.01) from the control> 0.001)

Table 2: Cesarean Section Observations^b

Observation	Dose (ml/kg)
	0	0.25	1.0	2.5
# Animals Assigned (Mated)	22	21	21	23
# Pregnancy Rate (%)	88	84	84	92
# Nonpregnant (%)	12	16	16	8
Maternal Wastage # Died	0	0	0	0
Total # Corpora Lutea Corpora Lutea/Dam	12.4 (1.2)	11.8 (1.5)	12.0 (0.9)	12.0 (1.2)
Total # Implantations (Implantations/Litter)	10.0 (3.0)	10.7 (2.5)	10.1 (1.9)	10.8 (1.6)
Total # Litters	22	21	21	23
Total # Live Fetuses (Live Fetuses/Litter)	9.5 (3.0)	10.2 (2.7)	9.8 (2.0)	10.4 (1.9)
Total # nonviable implants/litter Early resorptions Late resorptions Dead fetuses	1.6 (1.7) 0.3 (0.6) 0.1 (0.3) 0.3 (0.9)	0.2 (0.5)* 0.3 (0.5) 0.1 (0.4) 0.1 (0.3)	1.1 (1.6) 0.2 (0.4) 0.0 (0.2) 0.1 (0.4)	0.6 (0.7) 0.4 (0.6) 0.0 (0.0) 0.3 (0.5)
Mean Fetal Weight (g) Males Females	4.38 (0.21) 4.17 (0.26)	4.42 (0.15) 4.16 (0.14)	4.44 (0.29) 4.15 (0.23)	4.35 (0.19) 4.08 (0.25)
Sex Ratio (% Male)	43.6 (21.1)	41.5 (15.6)	51.3 (13.9)	53.3 (12.0)
Preimplantation Loss (%)	19.7 (24.2)	10.1 (16.9)	15.9 (14.6)	10.1 (12.0)

a Data extracted from pg 445 of the study report.

b Mean (±S.D)
*  Significantly different (p 0.05) from the control.>0.05)
** Significantly different (p 0.01) from the control.>0.01)

Table 3: Malformations Observed in Fetuses ^a

Observations+	Dose (ml/kg)
	0	0.25	1.0	2.5
#Fetuses(litters) examined	210 (22)	215 (21)	206 (21)	240 (23)
#Fetuses(litters) affected	0 (0)	1 (1)	2 (1)	3 (3)
External malformations ·          Left ear displaced dorsally and anteriorly	0 (0  )	0 (0  )	0 (0  )	1 (1  )
Visceral malformations
·          Hole in the heart from left ventricle to right atrium	0 (0)	1 (1)	0 (0)	0 (0)
·          Incomplete closure of the nasopharynx	0 (0)	0 (0)	0 (0)	1 (1)^b
·          Circular hole in right cerebral hemisphere	0 (0)	0 (0)	0 (0)	1 (1)^b
·          Depression in soft palate covered by a very thin membrane	0 (0)	0 (0)	0 (0)	1 (1)^b
·          Incomplete closure of hard palate around median raphe	0 (0)	0 (0)	0 (0)	1 (1)^b
·          Cleft palate-hard and soft	0 (0)	1 (1)	1 (1)	0 (0)
Skeletal malformations ·        Ribs No. 8 and No. 7 fused on right side	0 (0)	0 (0)	1 (1)	0 (0)

⁺Some observations may be grouped together

^aDataextracted from pg 446 of the study report.

^b The same fetus exhibited all of the indicated visceral findings.

*  Significantly different (p 0.05) from the control.>0.05) 

Table 4: Significant Variations Observed in Fetuses ^a

Observations+	Dose (ml/kg)
	0	0.25	1.0	2.5
#Fetuses(litters) examined	22	21	21	23
#Fetuses(litters) affected	0 (0)	1 (1)	2 (1)	3 (3)
External variations	0 (0  )	0 (0  )	0 (0  )	0 (0)
Skeletal variations
·          Anterior Arch of the Atlas bilobed	0 (0)	0 (0)	5 (5*))	0 (0)
·          Bone island associated with cervical arch No. 7, unilateral	3 (2)	2 (2)	8 (8*)	3 (2)
·          Thoracic centrum No. 1 bilobed	48 (17)	49 (21*)	54 (19)	71 (23*)
·          Some (1-4) proximal phalanges (forelimb) poorly assified	35 (15)	26 (14)	38 (18)	71 (22*)
·          Some (1-4) metatarsals (hindlimb) poorly ossified	7 (7)	1 (1*)	5 (5)	6 (6)
Visceral variations ·        Lateral ventricles of cerebrum dilation	4 (1)	5 (5)	5 (5)	11 (9)*

⁺Some observations may be grouped together

^aDataextracted from pg 447 of the study report.

*  Significantly different (p 0.05) from the control.>0.05) versus the controls

 

Applicant's summary and conclusion

Conclusions:

There was no evidence of embryotoxicity or teratogenicity at any of the dose levels employed under the conditions of this study.

Executive summary:

Timed pregnant Fischer 344 rats were dosed with β-(3,4 -epoxycyclohexyl)ethyltrimethoxysilane in corn oil by gavage on gestational days 6 through to 15 at doses of 0, 0.25, 1.0 and 2.5 ml/kg. At termination on gestational day 21 live fetuses were examined for external, visceral and skeletal alterations. Maternal toxicity was observed at 1.0 and 2.5 ml/kg, as evidenced by reduced body weight gain and food consumption during treatment, clinical signs of toxicity, reduced body weight on gestation day 21 (corrected for gravid uterine weight), and increased relative liver weight. There were no significant differences among groups on pre- or postimplantation loss, fetal/litter body weight, or on the incidence of malformations. Minimal fetal toxicity, dilated lateral cerebral ventricles and reduced ossification in the forelimbs was observed at 2.5 ml/kg. No embryotoxicity or teratogenicity was observed at any dose.