2,11-Dioxa-3,10-disiladodecane, 3,3,10,10-tetramethoxy-

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-09-28 to 2009-12-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: OECD 422 Combined repeated dose toxicity study with the reproduction/developmental toxicity screening test

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 001

Cas Number:

87135-01-1

Molecular formula:

C12H30O6Si2

Constituent 2

Reference substance name:

3,3,10,10-tetramethoxy-2,11-dioxa-3,10-disiladodecane

EC Number:

617-969-6

Cas Number:

87135-01-1

Molecular formula:

(CH3O)3Si(CH2)6Si(OCH3)3 C12 H30 O6 Si2

IUPAC Name:

3,3,10,10-tetramethoxy-2,11-dioxa-3,10-disiladodecane

Test material form:

other: liquid

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: no details
- Age at study initiation: 9 wks
- Weight at study initiation: Males: 270.2-352.6 g; Females: 199.2-233.1 g
- Housing: 1/suspended wire mesh cage (except during mating, gestation, lactation and urine analysis). During mating 1 female:1 male in the home cage of the male. After positive evidence of mating - shoebox cages. During lactation dams were housed with their litters. For urine collection (the day prior to necropsy) - stainless steel metabolism cages (without feed).
- Use of restrainers for preventing ingestion (if dermal): no
- Diet: standard diet ad libitum
- Water: drinking water ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19.7-22.8
- Humidity (%): 14->70 (guideline indicates 30-70 except during cleaning). One occurrence each of 14% and 29% RH were recorded - these were brief and not considered to affect the overall findings of this study.
- Air changes (per hr): approximately 13.1
- Photoperiod (hrs dark / hrs light): 12 h/12 h

IN-LIFE DATES: From: 2009-09-28 presumably for up to 55 days

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Prepared 4 times during study, analysed for dose concentration (GC/FID). The lowest dose was analysed for stability and homogeneity during this study, the two higher concentrations were analysed for stability and homogeneity in a similar previous study with the same test material at similar concentrations.

VEHICLE
- Justification for use and choice of vehicle (if other than water): corn oil was considered an appropriate vehicle for oral administration.
- Amount of vehicle (if gavage): total administered volume 3 ml/kg bw
- Lot/batch no. (if required): not given
- Purity: not given

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

GC/FID (no further details given in the first 105 pages of this report that have been supplied and reviewed).

Details on mating procedure:

- Impregnation procedure: cohoused
- M/F ratio per cage: 1:1
- Length of cohabitation: continuously until evidence of mating
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

daily, 7 days/week for 55 consecutive days to females (and 29 consecutive days to males).

Frequency of treatment:

daily

Duration of test:

55 days females (29 days males)

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: none identified in the report.
- Rationale for animal assignment: weight-stratified randomization.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at least daily.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: prior to first dose and weekly thereafter.
Observations included: changes in skin, fur, eyes, mucous membranes, secretions, excretions, autonomic activity (e.g. lacrimation, piloerection, pupil size, respiratory pattern), changes in gait and posture, response to handling, presence of clonic or tonic movements, stereotypies (e.g. excessive grooming, repetitive circling), bizarre behaviour, difficult parturition.

BODY WEIGHT: Yes
- Time schedule for examinations: prior to randomization, at the first dose, then at least weekly.

FOOD CONSUMPTION AND COMPOUND INTAKE :
- Food consumption for each animal determined: at least weekly.

WATER CONSUMPTION AND COMPOUND INTAKE: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice: females after 55 days, on post-natal day (PND) 4.
- Organs examined:

GROSS NECROPSY
All adult animals - complete gross necropsy (external surfaces, orifices, cranial, thoracic and abdominal cavities).

Females - number of corpora lutea, implantation sites.

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in Table 2 from the control and high dose groups were prepared for microscopic examination and/or weighed.

The following tissues were also taken from mid-dose females: urinary bladder, kidney, stomach and liver.

IMMUNOHISTOCHEMISTRY
The microscopic findings in the kidney were not indicative of alpha 2U globulin accumulation and therefore tissues were not sent for immunohistochemical staining

OTHER:
Duration of gestation.

Functional Observational battery and Motor Activity evaluations: on all rats prior to dosing and on post-natal day (PND) 4 for females. These comprised: cage side observations (abnormal muscle movements or behaviour, posture, resistance to removal from the cage), hand-held observations (including pupil size and reactivity, salivation, muscle tone, reactivity to handling), open field observations (level of activity, responsiveness to sharp noise, touch or tail pinch, gait, urine and faecal pellets voided), categorical observations, measurement/counts (rectal temperature, grip strength, landing foot splay), motor activity (using Cage Rack Activity System).

Urinalysis: Physical examination (colour, appearance, volume, specific gravity), pH, bilirubin, nitrite, blood, glucose, protein, leukocytes, ketones, urobilinogen.

Haematology and clinical chemistry (see table 1).

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes - at PND4
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

Dead pups and pups terminated on PND4 were only examined for external gross abnormalities.

- External examinations: Yes: all per litter
- Soft tissue examinations: No
- Skeletal examinations: No
- Head examinations: No

Statistics:

ANOVA: body weight changes, organ weights, food consumption, haematology, clinical chemistry, prothrombin times. Also log or rank transformation, Kruskal-Wallis test, Dunnett’s Test (SAS v9.1.3).
Statistical analysis of urinalysis data, FOB, motor activity, reproductive parameters and histopathology (SAS v9.1.3).

Indices:

Corpora lutea, total implants, pre-implantation loss, post-implantation loss, gestation duration.
Total pups post-natal day (PND) 0, sex of pups, viable pups PND0 and PND4, litter weight PND0 and PND4, average pup weight PND0 and PND4, post-natal loss%

Historical control data:

Historical data from this laboratory are referred to in the description of biological significance of certain effects. None are presented in the summary pages (1-105) that have been seen of this report. Pages 106 to around 500 contain the individual animal data and also appear not to include historical data.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Dose-related test article effects – results for controls (0), 300, 3000 and 1000 mg/kg bw/day groups, out of groups of 10 in each case:

Muzzle soiling: 5, 2, 8, 10 (f); repetitive paw pressing (transient after dosing): 0, 2, 7, 10 (f)

No clear effect on body weight in females.

Statistically significant increase in food consumption in 1000 mg/kg bw/day females during study days 1-8 (13.4%), gestational days (GDs) 0-7 (10.5%) and in overall food consumption (2.7%). An increase in food consumption was seen 30 mg/kg bw/day females during GDs 0-7 (10.6%). No toxicological significance was attributed to this effect.

No treatment-related statistically significant difference in FOB categories or motor activity data.

Top dose females had increased cholesterol (33% compared to concurrent controls) – the mean and individual values were within the historical range. The finding was considered not toxicologically significant.

No significant treatment-related haematological effects in female rats.

Females in the 30 and 1000 mg/kg bw/day groups had reduced urinary pH (5% and 11%, respectively) compared to concurrent controls. This effect was not considered toxicologically significant. (There were no treatment-related effects on urine in males.)

Organ weights.
30 and 1000 mg/kg bw/day females had increased absolute kidney weight. 1000 mg/kg bw/day females had increased absolute liver weight. No other absolute or relative changes in organ weights in females.

One 300 mg/kg bw/day females was non-gravid despite evidence of mating, one 1000 mg/kg bw/day female failed to mate. Other females produced litters similar in all respects to those of controls (number of live borne pups, litter weight, survival).

Gross examination:
Kidney effects: discoloured (pale and or mottled) kidneys (0, 0, 3, 5 (f)).

Microscopic examination:
Clear lesions the kidneys of all males and one female at 1000 mg/kg bw/day (varying lesions described as obstructive nephropathy). The two most severely and bilaterally affected animals had other lesions (mineralization of the stomach and/or aorta) indicating they were uremic (had renal failure). The characteristic kidney lesions included: foci of pale staining globular material in the cortex or medulla, multinucleated phagocytic cells, necrotic epithelial cells, dilated tubules filled with necrotic cells and exudate, interstitial infiltration of neutrophils and lymphocytes, papillary necrosis, hyperplasia and inflammation of renal pelvis.

Hyperplasia of the urinary bladder epithelium was reported in most treated rats (statistically significant in all treated males and in females at >=300 mg/kg bw/day). In the more severely affected (typically at higher doses) the hyperplasia was associated with inflammation of the submucosa, with granulomatous inflammation associated with pale globular deposits (similar to that in the kidneys), in one case. The globular deposit was recorded as a calculus and considered to have caused acute urinary obstruction. Combining the various forms of inflammation, this effect was statistically significant at >=300 mg/kg bw/day in both sexes.

Significant minimal centrilobular hepatocyte hypertrophy in 9/10 females at 10000 mg/kg bw/day, considered an adaptive change to the treatment. Decreased periportal vacuolation in 1000 mg/kg bw/day males probably due to the depletion of glycogen stores under stress.

Diffuse gastric gland dilation (significant-mild) occurred in all females at 1000 mg/kg bw/day with occasional single necrotic cells in these dilated glands; the controls were not affected.

Other findings were sporadic and/or typical of rats of this age and stock and considered not to be treatment-related.

Based on urinary bladder epithelium hyperplasia the NOAEL for systemic effects is 30 mg/kg bw/day for females.

Effect levels (maternal animals)

1

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: developmental toxicity

Remarks on result:

other:

Remarks:

Absence of treatment-related developmental effects at the highest dose tested.

2

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Remarks on result:

other:

Remarks:

Effects on the urinary bladder epithelium in females treated with 300 mg/kg bw/day for up to 55 days.

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
One 300 mg/kg bw/day females was non-gravid despite evidence of mating, one 1000 mg/kg bw/day female failed to mate. Other females produced litters similar in all respects to those of controls (number of live born pups, litter weight, survival to PND 4). No treatment-related reproductive or developmental effects were identified (see table 3). NOAEL (developmental effects) >1000 mg/kg bw/day/

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

> 1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Overall effects

Remarks on result:

other: Overall effects

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Table 3: Summary of reproductive/developmental measurements

Parameter	Dose in mg/kg bw/day
	0	30	300	1000
Corpora Lutea counts	17.7	19.3	19.3	17.7
Total implants	14.8	15.6	13.5	14.1
Pre-implantation loss%	15.6	17.8	32.6	17.9
Post implantation loss%	8.9	5.1	9.5	8.3
Gestation days	22	22	22	22
Total pups PND0	13.7	14.9	13.7	14.8
Viable pups PND0	13.6	14.8	13.6	14.4
Males/females PND0	1.0	1.5	1.6	1.1
Litter weight PND0	87.2	95.8	85.7	93.3
Average pup weight PND0	6.5	6.5	6.4	6.5
Total pups PND4	13.6	14.8	13.4	14.4
Viable pups PND4	13.6	14.8	13.4	14.4
Males/females PND4	0.97	1.37	1.24	1.01
Litter weight PND4	134.6	150.6	135.1	140.6
Average pup weight PND4	10.2	10.2	10.2	9.9
Postnatal loss%	0.0	0.0	0.8	0.0

PND: post-natal day

None of the above data were said to indicate any statistically significant treatment-related effect

Applicant's summary and conclusion

Conclusions:

A well reported combined repeated dose toxicity study with reproductive/developmental toxicity screening test, conducted according to the current guideline (OECD 422) and GLP, found that gavage administration of up to 1000 mg/kg bw/day to male and female rats from 2 weeks prior to mating was not associated with developmental toxicity. Systemic effects were reported in the dams at 300 mg/kg bw/day. The NOAEL for developmental toxicity is >1000 mg/kg bw/day based on the screening element of this study.