Silanediol, 1-methyl-1-(1-methylethoxy)-, 1,1-diacetate

Toxicity to reproduction

Administrative data

Endpoint:

screening for reproductive / developmental toxicity

Remarks:

based on test type (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2002

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:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

442-070-9

EC Name:

-

Cas Number:

329039-38-5

Molecular formula:

Hill formula: C8 H16 O5 Si CAS formula: C8 H16 O5 Si

IUPAC Name:

(acetyloxy)(methyl)(propan-2-yloxy)silyl acetate

Details on test material:

- Name of test material (as cited in study report): methyldiacetoxyisopropoxysilane
- Physical state: clear, colorless liquid
- Analytical purity: 85.8 %
- Impurities (identity and concentrations): 12.9 % Acetoxydiisopropoxymethtylsilane, 1.3 % hydrolisis product (siloxane)
- Purity test date: 04.10.2001
- Batch No.: AA001 (04.10.01)
- Storage condition of test material: Below 30 °C in an airtight container under nitrogen under the hood

Test animals

Species:

rat

Strain:

other: albino CD® (Sprague-Dawley) rats ( CrI:CD®[SD] IGS BR)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Raleigh, NC
- Age at study initiation: approximately ten weeks
- Weight at study initiation: males: 315.3 to 362.6 g; females: 212.9 to 255.2 g
- Housing: individually housed during the quarantine period and upon the initiation of the treatment period in solid-bottom polycarbonate cages with stainless-steel wire lids (LaboratoryProducts, Rochelle Park, NJ) with Sani-Chip® cage litter (p.J. Murphy Forest Products Corp., Montville, NJ);study animals two per cage (one male:one female from the same dose) during mating period; females separately and individually post mating; selected F1 male and female weanlings singly housed during the postwean period.
- Diet: Purina Certified Rodent Chow (No. 5002, PMI Feed), ad libitum.
- Water: tap water, ad libitum
- Acclimation period: quarantined for approx. one week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30 - 70
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Dosing solutions were prepared at the morning of each dosing day by adding vehicle to a precalibrated tared beaker containing the test material

VEHICLE
- Justification for use and choice of vehicle (if other than water): Corn oil with 0.1 % water, because acetoxysilane decomposes rapidly in water
- Concentration in vehicle: 5, 15 and 45 mg/mL
- Amount of vehicle (if gavage): 5 mL/kg bw
- Lot/batch no. (if required): Mazola®
- Purity: 99.9 % with 0.1 % water

Details on mating procedure:

- M/F ratio per cage: 1/1
- Length of cohabitation: 2 weeks
- Proof of pregnancy: vaginal plug / 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): individually

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

For analysis of the dosed formulations, content was based on the analysis of the major breakdown product, methylacetoxydiisopropoxy silane. Each sampIe was analyzed by single injection using capillary gas chromatography. The concentration of acetoxysilane was calculated in the dose formulation sampIes (mg/mI) from the peak area ratio for each sampIe and the linear regression equation.
For stability studies, the doses mixed for the low and high homogeneity studies were removed from the storage condition on the day of sampling (2, 4, and 7 days) and brought to ambient conditions. The formulations were stirred prior to sampling. Triplicate 1 g aliquots were removed and analyzed as described above. Dose formulations were not stable for two days when stored in the refrigerator (80.9% recovery for low dose; 131% recovery for high dose). Recovery values for days 4 and 7 were 37.1% and 43.3% for the low dose, respectively. Vehicle control formulations contained no acetoxysilane, with an estimated detection limit of 0.4 mg/mL.

Duration of treatment / exposure:

F0 females: 10 weeks throughout the whole study
F0 males: 6 weeks
F1 females: 7 weeks from postnatal Day 21
F1 males: 7 weeks from postnatal Day 21

Frequency of treatment:

once daily, 7 days/week

Doses / concentrations

Remarks:

Doses / Concentrations:
25, 75, and 225 mg/kg bw/day
Basis:
other: calculated doses

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The doses were chosen based on a range-finding study, employing doses of 0, 100, 300, and 1000 mg/kg bw/day, administered by oral gavage at 5 mL/kg for ten days. There was profound toxicity (including morbidity) in both sexes at 1000 mg/kg bw/day, evidence of toxicity at 300 mg/kg bw/day, and the possibility of effects on ovarian weights at 100 mg/kg bw/day in the range-finding study.
- Rationale for animal assignment (if not random): by means of randomization stratified by body weight
- Rationale for selecting satellite groups: 5 males from control and high dose group
- Post-exposure recovery period in satellite groups: 2 weeks

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily


DETAILED CLINICAL OBSERVATIONS: Yes, including, but not limited to, changes in: skin and fur, eyes, mucous membranes, respiratora and circulatory system, autonomic and central nervous system, somatomator activity and behavior pattern.
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: Initially and then weekly

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

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at necropsy
- Anaesthetic used for blood collection: No
- Animals fasted: Yes, overnight
- How many animals: 5 / sex
- Parameters red blood cell (RBC), white blood cell (WBC), and platelet (PLT) counts; hemoglobin concentration (HGB); hematoerit (HCT); red cell
distribution width (RDW); mean platelet volume (MPV); the red blood cell indices mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC); and prothrombin time (PT) were analysed.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at necropsy
- Animals fasted: Yes, overnight
- How many animals: 5 / sex
- Parameters albumin, asparatate aminotransferase (AST), alanine aminotransferase (ALT), urea nitrogen (BUN), total cholesterol, creatinine, glucose, total protein and the electrolytes sodium, potassium, and chloride were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: Prior to necropsy, five parental males per group (selected randomly) were housed in metaboism cages overnight and urine was collected.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No
- Parameters glucose, bilirubin, ketones, specific gravity, blood, pH, protein, urobilinogen, nitrite, and leukocytes were examined.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: weekly
- Dose groups that were examined: all
- Battery of functions tested: sensory and neuromuscular activity

Sperm parameters (parental animals):

Parameters examined in P male parental generations:
testis weight, epididymis weight, sperm count in testes, sperm count in epididymides, enumeration of cauda epididymal sperm reserve, sperm morphology

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- If yes, maximum of 10 pups/litter (5/sex/litter as nearly as possible); excess pups were killed and discarded.

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 behavioral abnormalities
F1 post weaning observations and procedures for each retained female included examination for vaginal patency (VP; from pnd 22 until acquisition of VP) and determination of estrus cyclicity and normality evaluated by vaginal smears taken daily the last three weeks of the postwean exposure period prior to scheduled sacrifice.

GROSS EXAMINATION OF DEAD PUPS:
Yes, All pups dying during lactation were necropsied, when possible, to investigate the cause of death.

Postmortem examinations (parental animals):

GROSS PATHOLOGY: Yes, Ovaries (pair), Prostate, Epididymides (pair), Uterus with cervix and vagina, Testes (pair), Seminal vesicles with coagulating glands and their fluids (pair), Spinal cord, Thyroid, Stomach, Urinary bladder, Peripheral nerve (sciatic nerve), Bone marrow (femur), Small and large intestines (including Peyer's patches), Trachea and lungs (preserved by inflation with fixative and then immersion fixed), Lymph nodes (one cervical, near route of administration; and one mesentric, distant from the route of administration), All gross lesions,
HISTOPATHOLOGY: Yes

Postmortem examinations (offspring):

SACRIFICE
- The F1 offspring were sacrificed at 70 days of age.
- These animals were subjected to postmortem examinations (macroscopic and/or microscopic examination) as follows:

GROSS NECROPSY
- hematology, clinical biochemistry, and urinalysis (males only) assays at necropsy for five F1 adult males and five F1 females per dose group.
- Ovaries (pair), Prostate, Epididymides (pair), Uterus with cervix and vagina, Testes (pair), Seminal vesicles with coagulating glands and their fluids (pair), Spinal cord, Thyroid, Stomach, Urinary bladder, Peripheral nerve (sciatic nerve), Bone marrow (femur), Small and large intestines (including Peyer's patches), Trachea and lungs (preserved by inflation with fixative and then immersion fixed), Lymph nodes (one cervical, near route of administration; and one mesentric, distant from the route of administration), All gross lesions
- Sperm motility (motile and progressively motile) was assessed immediately after necropsy for all males; number and morphology (at least 200 sperm per male, if possible) was evaluated using appropriately retained sperm sampIes initially from the high dose and control males.

HISTOPATHOLOGY: Yes

Statistics:

Treatment groups were compared to the concurrent control group using either parametric ANOVA under the standard assumptions or robust regression methods (Zeger and Liang, 1986; RoyalI, 1986; Huber, 1967) that do not assume homogeneity of variance or normality. The homogenity of variance assumption was examined via Levene's Test (Levene, 1960), which is much more robust to the underlying distribution of the data than the traditional Bartlett's Test. If Levene's Test indicated lack of homogeneity of variance (p<0.05), robust regression methods were used to test all treatment effects.
Frequency data such as reproductive indices (e.g., mating and fertility indices) were not transformed. All indices were analyzed by Chi-Square Test for Independence for differences among treatment groups (Snedecor and Cochran, 1967) and by the Cochran-Armitage Test for Linear Trend on Proportions (Cochran, 1954; Armitage, 1955; Agresti et al., 1990). If Chi-Square revea1ed significant (p<0.05) differences among groups, then a Fisher's Exact Probability Test, with appropriate adjustments for multiple comparisons, was used for pairwise comparisons between each treatment group and the control group.

Reproductive indices:

Mating index, Fertility index, Gestational index (females), Pregnancy index (males), Pereent Postimplantation Loss per Dam and Arcsine Root Transformation, Stillbirth Index per Dam and Arcsine Root Transformation, Live Birth index per Dam and Arcsine Root Transformation, Four-Day Survival index per Dam and Arcsine Root Transformation, Percent Males per Litter and Arcsine Root Transformation, Average Pup Body Weight per Litter, Average Male Pup Body Weight per Litter, Average Female Pup Body Weight per Litter

Offspring viability indices:

Live birth index, 4-Day survival index, 7-Day survival index, 14-Day survival index, 21-Day survival index, Lactation index

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

at 225 mg/kg/day

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:

effects observed, treatment-related

Description (incidence and severity):

225 mg/kg/bw: effects on stomach

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

no effects observed

Details on results (P0)

CLINICAL SIGNS AND MORTALITY
audible breathing in two females, found dead or euthanized moribund in three females, rooting postdosing in ten females, and gasping, rough coat, and rooting prior to dosing in one female each at 225 mg/kg/day

NEUROBEHAVIOUR
During week 3 (the first week of the mating period), average muscle tone score per animal and average tail pinch response score per animal were significantly reduced at 225 mg/ kg/day. The percent animals with abnormal (depressed) arousal was significantly higher at 225 mg/kg/day during week 3.

HISTOPATHOLOGY:
In the stomach at 225 mg/kg/day: epithelial degeneration (five of five males) and acute inflammation of the forestomach (one of five), and acute inflammation of the glandular portion of the stomach (one of five).

Effect levels (P0)

1

Dose descriptor:

NOAEL

Remarks:

Parental toxicity

Effect level:

75 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: clinical signs, histopathology, neurobehavior

2

Dose descriptor:

NOAEL

Remarks:

Reproductive Toxicity

Effect level:

225 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

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:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings:

no effects observed

Details on results (F1)

No effects observed

Effect levels (F1)

Dose descriptor:

NOAEL

Remarks:

Offspring toxicity

Generation:

F1

Effect level:

225 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

In this study the no observable adverse effect level (NOAEL) for systemic parental toxicity was 75 mg/kg/day; for reproductive and offspring toxicity, the NOAEL was >=225 mg/kg/day. Therefore, methyldiacetoxyisopropoxy silane has not to be classified for reproduction toxicity according to DSD and CLP.

Executive summary:

In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test according to OECD guideline 422 (Tyl, 2002) male and female rats were treated with 25, 75 and 225 mg/kg bw/day methyldiacetoxyisopropoxysilane. Female rats were treated daily for 10 weeks, male rats daily for 6 weeks. Furthermore the F1 generation was treated from weaning (pnd 21), for approximately seven more weeks (dosing for F1 selected pups began on pnd 22 and continued until all pups were at least 70 days of age). Only mild systemic toxicity in F0 parental males at 225 mg/kg/day was observed, expressed as sporadic effects on hematologic and neurobehavioral parameters and histopathologic lesions in the stomachs of F0 (but not Fl) males. There were no treatment- or dose-related effects on absolute organ weights or organ weights relative to terminal body or brain weights, or on gross findings, clinical chemistry, or urinalysis. There was no evidence of F0 reproductive toxicity in either sex at any dose. However, there were no effects on Fl male reproductive system histopathology or andrology at any dose. There was no other evidence of Fl offspring toxicity, either pre- or postnatally. There were no effects of treatment on acquisition of puberty in either sex and no changes in Fl adult male reproductive tract histopathology or andrology. In conclusion, administration of methyldiacetoxyisopropoxysilane by gavage once daily at 0, 25, 75, or 225 mg/kg bw/day to parental F0 rats, ten/sex/group, through prebreed, mating, gestation, and lactation, and direct dosing to F1 offspring from weaning to scheduled sacrifice on or about pnd 70, resulted only in minimal adult F0 parental toxicity at 225 mg/kg/day. Therefore, under the conditions of this study, the no observable adverse effect level (NOAEL) for systemic parental toxicity is 75 mg/kg/day; for reproductive and offspring toxicity, the NOAEL is >=225 mg/kg/day.