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Toxicological information

Repeated dose toxicity: oral

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Administrative data

sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)
GLP compliance:
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Test material form:
other: liquid
Details on test material:
- Name of test material (as cited in study report): Triethoxy(2,4,4-trimethylpentyl)silane

- Physical state: liquid, colourless, transparent

- Storage condition of test material: room temperature, protected from humidity (air)

Test animals

Details on test animals or test system and environmental conditions:
- Source: Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: males: 7-8 weeks old, females: 7-8 weeks old.
- Weight at study initiation: males: 151.1 – 184.6 g; females: 122.0 – 148.1 g
- Fasting period before study: not indicated
- Housing: Animals of the same sex were housed in groups of up to five in type IV polysulphone cages on Altromin saw fibre bedding (lot no. 02102140605)
- Diet (e.g. ad libitum): Free access to Altromin 1324 maintenance diet for rats and mice (lot no. 1526)
- Water (e.g. ad libitum): Free access to tap water, sulphur acidified to a pH of approximately 2.8 (drinking water, municipal residue control, microbiological controls at regular intervals)
- Acclimation period: minimum 5 days

- Temperature (°C): 22 ± 3°C
- Humidity (%): 55 ± 10%
- Air changes (per hr): 10 x / hour
- Photoperiod (hrs dark / hrs light): Artificial light, sequence being 12 hours light, 12 hours dark

Administration / exposure

Route of administration:
oral: gavage
corn oil
Details on oral exposure:
The test item formulation or vehicle was administered at a single dose to the animals by oral gavage. The application volume for all groups was 5 mL/kg body weight.

For each animal the individual dosing volume was calculated on the basis of the body weight most recently measured.

The doses were selected in consultation with the sponsor.

Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
Stability of the dosing formulations was tested once at the beginning of the treatment period. In the first week of treatment, at the beginning of the second month of treatment and at the end of the treatment period, samples for the testing of homogeneity were taken from the top, middle and bottom of the freshly prepared high and low-dose formulations and stored between -15 and -35 °C.
Duration of treatment / exposure:
90 days
Frequency of treatment:
Daily, 7 days per week
Doses / concentrationsopen allclose all
Dose / conc.:
15 mg/kg bw/day (actual dose received)
Dose / conc.:
50 mg/kg bw/day (actual dose received)
Dose / conc.:
150 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
Details on study design:
The highest dose level was chosen with the aim of inducing toxic effects, but no death or severe suffering. Thereafter, a descending sequence of dose levels was selected with a view to demonstrate any dosage related response and NOAEL.
The animals in the control group were handled in an identical manner to the test group subjects and received corn oil using the same volume as used for the high dose group.


Observations and examinations performed and frequency:
- Time schedule: once before the first administration and at least once a week thereafter

- Time schedule: Minimum once a day, twice daily all animals were observed for morbidity and mortality except on weekends and public holidays when observations were made once daily.

- Time schedule for examinations: The body weight was recorded once before the assignment to the experimental groups, on the first day of administration and weekly during the treatment and recovery period.

- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No, food consumption was measured weekly during the treatment and recovery period.

- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

- Time schedule for examinations: Ophthalmological examination, using an ophthalmoscope was made at the first administration and in the last week of the treatment period.
- Dose groups that were examined: All animals, as well as at the end of the recovery period in the recovery animals.

- Time schedule for collection of blood: At the end of the treatment and recovery period, prior to or as part of the sacrifice of the animals.
- Anaesthetic used for blood collection: No data
- Animals fasted: Yes
- Parameters checked: haematocrit, haemoglobin content, red blood cell count, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular concentration, reticulocytes, platelet count, white blood cells, neutrophils, lymphocytes, monocytes, eosinophils, basophils, large unstained cells, coagulation parameters (prothrombin time, activated partial thromboplastin time)

- Time schedule for collection of blood: at the end of the treatment and recovery period prior to or as part of the sacrifice of the animals
- Animals fasted: No data
- Parameters checked: alanine aminotransferase, aspartate-aminotransferase, alkaline phosphatase, creatinine, total protein, albumin, urea, total bilirubin, total bile acids, total cholesterol, glucose, potassium, sodium

- Time schedule for collection of urine: prior to or as part of the sacrifice of the animals
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters checked: specific gravity, nitrite, pH, protein, glucose, ketone bodies, urobilinogen, bilirubin, blood, leukocytes.

- Time schedule for examinations: Once before the first exposure and once in the last week of the recovery period.
- Dose groups that were examined: All animals
- Battery of functions tested: other: sleep, moving around cage, piloerection, vocalisation, grooming, grip strength, visual palcing, positional passivity, equilibrium reflex, startle response, sterotypical behaviour, unusual behaviour, seizures, twitches, tremors, gait etc.

Sacrifice and pathology:

-Organs weighed at necropsy: liver, kidneys, adrenals, testes, epididymides, prostate, seminal vesicles, coagulating glands, ovaries, uterus with cervix, thymus, thyroid/parathyroid glands, spleen, brain, pituitary gland, heart. The wet weight of the organs of all sacrificed animals was taken from sacrificed animals as soon as possible. Paired organs were weighed together.

-Preserved and examined tissues: brain, spinal cord, eye, liver, kidneys, adrenal glands, stomach, heart, ovaries, uterus with cervix, vagina, testes, apididymides, prostrate and seminal vescles with coagulating glands as a whole. Small and large intestines, thymus, thyroid glands, spleen, lung and trachea, mammary glands, skin, urinary bladder, lymphnodes, perpheral nerve with skeletal muscle, sternum with bone marrow, pituitary gland, oesophagus


Results and discussion

Results of examinations

Clinical signs:
no effects observed
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 specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
No mortality occurred in the control or any of the dose groups during the treatment period of this study.

No test item related clinical findings were observed in this study. The clinical findings were either rare incidental findings or were observed in similar frequency also in control animals. The effects are not considered to be adverse.

No relevant effects were observed in any of the parameters of the functional observation battery with no biologically relevant differences in body temperature between the groups.

The body weight development of all groups was within the expected range of variation with no test item related effects. In accordance to the body weight development no effects on food consumption were recorded.

No influence of triethoxy(2,4,4-trimethylpentyl)silane on any of the analyzed parameters of hematology and blood coagulation independent of the gender of the animals was observed at the end of the treatment and after the recovery period.

All clinical biochemistry parameters analyzed at the end of the treatment and recovery phase did not indicate toxicologically relevant findings which are related to the test item.

Abnormalities observed in urinalysis were incidental findings and are not assumed to be toxicologically relevant. Therefore the test item is assumed to show no effects on parameters of urinalysis.

The recorded pathological changes were either isolated findings, were observed in control animals or were related to female cycle and are therefore considered to be normal background alterations.

Changes in organ weights were either related to female cycle, rare single cases or within normal range of variation with no toxicological relevance
Histopathologically adaptive and therefore non-adverse urothelial hyperplasia with minor degree was found in the urinary bladder of males and females receiving 50 mg/kg/day and 150 mg/kg/day.

Formulation analytics revealed that all samples were stable; the nominal concentrations were confirmed for all dose groups and that all samples were homogenous.

Effect levels

Key result
Dose descriptor:
Effect level:
150 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: No adverse effects were observed in animals treated at doses of 15, 50 and 150 mg/kg bw/day.

Target system / organ toxicity

Critical effects observed:

Applicant's summary and conclusion

A NOAEL of 150 mg/kg bw/day was identified in a 90 day oral repeated dose toxicity study. There were no treatment related findings in any of the animals.