Tetramethyl orthosilicate

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

19.09.2002 to 30.04.2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP, and is therefore considered to be reliability 1. Read-across of the result is considered to be reliability 2.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2005

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)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Tetraethyl orthosilicate

EC Number:

201-083-8

EC Name:

Tetraethyl orthosilicate

Cas Number:

78-10-4

IUPAC Name:

tetraethyl orthosilicate

Details on test material:

- Name of test material (as cited in study report): Tetraethyl Orthosilicate
- Substance type: silicate
- Physical state: Liquid
- Stability under test conditions: Stability was proven
- Storage condition of test material: at 4oC protected from humidity

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, France.
- Age at study initiation: Males: 8 weeks; Females: 10 weeks.
- Weight at study initiation: Males: 283-339 g; Females: 213-285 g.
- Fasting period before study: None
- Housing: Individually in suspended wire-mesh cages.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: 9-11 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ±2
- Humidity (%): 50 ±20
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 30.09.2002 To: 9-21.11.2002 for principal and toxicity groups. From: 01.04.2004 to 30.4.2004 for complementary groups.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The test substance was mixed with the required quantity of vehicle at concentrations of 3.33, 16.66 and 33.33 mg/ml. The dosage forms were performed as follows: the required quantity of test substance was weighed into an appropriate container; 75% of the final volume of the vehicle was added and the preparation was homogenised with a magnetic stirrer. Sufficient vehicle was thereafter added to make the solutions up to the required volume. The vehicle for the control group was measured first, followed by preparation of the low and intermediate, then theh high dose forms to avoid contamination. Solutions were kept for up to 9 days.


VEHICLE
- Justification for use and choice of vehicle (if other than water): None given
- Concentration in vehicle: 3.33, 16.66 and 33.33 mg/ml
- Amount of vehicle (if gavage): Various depending on concentration
- Lot/batch no. (if required): 81K2204 and 062K0006
- Purity: No data

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

Throughout the pre-mating period (15 days), during the mating and post-mating periods until final sacrifice for the males (at least 4 weeks in total). Throughout pre-mating (15 days) and mating period, during pregnancy and lactation, until day 4 post-partum inclusive (or until sacrifice for un-mated females) for the females.
Three groups of 10 females received the test item and a fourth group received the vehicle under the same experimental conditions as males of the principal groups for at least 4 weeks in total.

Frequency of treatment:

daily

Doses / concentrations

Remarks:

Doses / Concentrations:
10, 50, and 100 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

Ten

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on a seven day range-finding study.
- Rationale for animal assignment (if not random): Random
- Rationale for selecting satellite groups: Complementary evaluation of motor activity and assessment of sensory reactivity to stimuli were performed on additional animals treated for at least 4 weeks under the same experimental conditions as above: three groups of 10 males and 10 females received the test item and a fourth group received the vehicle under the same experimental conditions as for the principal and toxicity groups for at least 4 weeks in total.
- Post-exposure recovery period in satellite groups: None
- Section schedule rationale (if not random): Random

Positive control:

None

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Morbidity and mortality checked at least twice daily. Clinical signs noted at least once per day.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Before the first day of treatment and then weekly thereafter.


BODY WEIGHT: Yes
- Time schedule for examinations: Principal males, toxicity females and complementary groups: first day of treatment (Day 1) and then once per week until sacrifice. Principal females: Day 1, then once per week until mating, and on Days 0, 7, 14 and 20 post-coitum and Days 1 and 4 post-partum.


FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes. Recorded once per week. For principal females: Once per week and over the following periods: Days 0-7, 7-14, 14-20 post-coitum, and Days 1-4 post-partum.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / No data


FOOD EFFICIENCY: No


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of the treatment period
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes, overnight
- How many animals: All males and females of toxicity groups
- Parameters checked in table No.1 were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of the treatment period
- Animals fasted: Yes
- How many animals: All males and females of toxicity groups
- Parameters checked in table No.1 were examined.


URINALYSIS: No


NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Before first treatment and shortly before terminal sacrifice.
- Battery of functions tested: All animals: touch escape/ease of removal from cage, fur appearance, chromodaccryorrhea, red/crusty deposits, eye, mucous membrane, skin colour, salivation, lacrimation, piloerection, exophthalmia, reactivity to handling, and pupil size. In the standard arena (2-minute recording): grooming, palpebral closure, defecation and urination counts, tremours, twitches, convulsions, gait, arousal (hypo- and hyperactivity), posture, stereotypic behaviour and breathing, ataxia, and hypotonia.
Principal males and toxicity females groups: landing footsplay, forelimb grip strength, rectal temperature.
Males and females of complementary groups: reactivity to manipulation or to different stimuli.
All males in principal group and females in toxicity group over 10 minute period AND all animals of complementary groups over a 60 minute period: motor activity.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 2)
HISTOPATHOLOGY: Yes (see table 2): A microscopic examination was performed on all tissues highlighted in table 2 for all males of the principal control and high-dose groups and for all females of the toxicity control and high-dose groups, examinations of the kidneys were performed in all males of the principal groups and all females of the toxicity groups at all dose-levels, all macroscopic lesions of all males and all females of the toxicity groups of the low- and intermediate-dose groups (groups 2 and 3) killed on completion of the treatment period. Special emphasis was paid to the stages of spermatogenesis in the male gonads and histopathology of interstitial testicular cell structure.

Other examinations:

None

Statistics:

Yes, for haematology, blood chemistry and organ weight data.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

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:

effects observed, treatment-related

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: No mortalities occurred. Excessive salivation was observed in many groups, but this was not considered an adverse effect. There were no other clinical effects.


BODY WEIGHT AND WEIGHT GAIN: There were some fluctuations in body weight/body weight gains; however, these were not treatment-related.


FOOD CONSUMPTION: There were no adverse effects on food consumption.


HAEMATOLOGY: No significant changes were noted. The were a few slight fluctuations, which were not dose-related or statistically significant.


CLINICAL CHEMISTRY: See Table 3. The slight decrease in sodium, potassium and chloride in males given 50 and 100 mg/kg bw/day was attributed to the marked tubular nephropathy observed at microscopic examination of the kidney of some males at the same dose levels. The values were within historical control levels, but the differences were dose-related and statistically significant, and therefore were considered to be treatment-related.


NEUROBEHAVIOUR: No adverse effect observed.


ORGAN WEIGHTS: There were no observed differences in males. A few differences in females were observed, but they were not dose-related, did not show the same trend in the two sexes and/or there were variations in the individual values between the treated and control groups, and/or within the same group. Therefore the differences were not considered to be of no toxicological importance.


GROSS PATHOLOGY: Principal and toxicity groups: Irregular colour or greyish/whitish areas of the kidneys in 1/10 males of the principal group and 1/10 females fom the toxicity group given 100 mg/kg bw/day. These findings correlated with degenerative/necrotic nephropathy and were considered treatment-related. No other treatment-related effects in other groups.


HISTOPATHOLOGY: See Table 4. Treatment-related changes were noted in the kidneys. Degenerative/necrotic nephropathy was observed among the treated animals at the dose-levels of 50 or 100 mg/kg bw/day. This was characterised by tubular dilatation with flattened epithelium, tubular epithelium degeneration/necrosis, vacuolated cortical tubular epithelium and/or granulocyte infiltration (inter- and intratubular in cortex and medulla).

Effect levels

Dose descriptor:

NOAEL

Effect level:

10 - 50 mg/kg bw/day (nominal)

Sex:

male/female

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 3 Blood Biochemistry for significant changes.

Dose (mg/kg bw/day)	0	10	50	100
Males
Sodium (mmol/L)	142.5	143.2	141.1*	140.3**
Potassium (mmol/L)	3.84	3.6	3.52**	3.65
Chloride (mmol/L)	104.5	105.4	102.6**	102.4**

*p<0.05, **p<0.01

Table 4 Summary of histopathological effects on the kidneys.

Dose (mg/kg bw/day)	Males				Females
	0	10	50	100	0	10	50	100
Kidneys
Degenerative/necrotic nephropathy
Grade 1 (minimal)			3/10	5/10				1/10
Grade 2 (slight)			1/10	4/10				2/10
Incidence	0/10	0/10	4/10	9/10	0/10	0/10	0/10	3/10
Mean severity			1.3	1.4				1.7

Applicant's summary and conclusion

Conclusions:

In a good quality OECD 422 study (reliability score 1) conducted to GLP, the parental NOAEL for tetraethylorthosilicate in rats was 50 mg/kg bw/day for the females and 10 mg/kg bw/day for the males, based on adverse effects on the kidneys (tubular nephropathy).