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

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

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): methyldiacetoxyisopropoxy silane
- 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
- Diet (e.g. ad libitum): Purina Certified Rodent Chow (No. 5002, PMI Feed), ad libitum.
- Water (e.g. ad libitum): 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 oral 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 0.01 % water

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/mL) 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
F0 males: 6 weeks

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

Observations and examinations performed and frequency:

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

Sacrifice and pathology:

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)
HISTOPATHOLOGY: Yes

Other examinations:

Reproductive and selected organs were weighed and organ weights were reported as absolute and relative to terminal body weight and brain weight: Ovaries (pair), Prostate, Epididymides (pair), Uterus with cervix and vagina, Testes (pair), Seminal vesicles with coagulating glands and their fluids (pair)

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.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

at 225 mg/kg/day

Mortality:

mortality observed, treatment-related

Description (incidence):

at 225 mg/kg/day

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

effects observed, treatment-related

Description (incidence and severity):

225 mg/kg/bw: reduced muscle tone, depressed arousal

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

225 mg/kg/bw: effects on stomach

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
audible breathing in two females, found dead or euthanized moribund in three females, rooting post dosing 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

Dose descriptor:

NOAEL

Effect level:

75 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: clinical signs, histopathology, neurobehavior

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Regarding the values from an oral repeated dose toxicity study in rats of a NOAEL of 75 mg/kg bw/day and a LOAEL of 225 mg/kg bw/day, Methyldiacetoxyisopropoxysilane is classified:
DSD: Not Classified
CLP: Not Classified

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. In conclusion, administration of 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 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 bw/day.