Dichlorocyclohexylmethylsilane

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

22 January 2019 to 11 February 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The aim of this 14-day dose-range finding study was to provide a basis for the selection of dose levels to be used in prenatal developmental toxicity study via oral (gavage) route. The dose-range finding study was planned to assess the possible health hazards, in particular local corrosive effects, which could arise from repeated exposure of dichloro(methyl)(phenyl)silane via oral administration to rats. Therefore, macroscopic and microscopic examinations of the animals were limited to the respiratory and gastrointestinal tracts.

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Dichloro(methyl)(phenyl)silane

EC Number:

205-746-2

EC Name:

Dichloro(methyl)(phenyl)silane

Cas Number:

149-74-6

Molecular formula:

C7H8Cl2Si

IUPAC Name:

Dichloro-methyl-phenylsilane

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation: 12-13 weeks old
- Weight at study initiation: males: 343 – 374 g; females: 205 – 234 g
- Fasting period before study: none
- Housing: kept in groups of 2 animals / sex / group / cage in IVC cages
- Diet (e.g. ad libitum): Free access to Altromin 1324 maintenance diet for rats and mice, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: at least 5 days

DETAILS OF FOOD AND WATER QUALITY: Certificates of food, water and bedding are filed for two years at BSL Munich and afterwards archived at Eurofins Munich

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22+/-3°C
- Humidity (%): 55+/-10%
- Air changes (per hr): 10 x / hour
- Photoperiod (hrs dark / hrs light): 12 hours light/ 12 hours dark

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The test item was dissolved in dried and de-acidified corn oil. The test item was weighed into a tared plastic vial on a suitable precision balance and the vehicle was added to give the appropriate final concentration of the test item. The formulation was alternately vortexed and/or stirred until visual homogeneity was achieved.

VEHICLE
- Justification for use and choice of vehicle (if other than water): The vehicle was selected in consultation with the sponsor based on the test item’s characteristics.
- Concentration in vehicle: 12.5, 25, 62.5, 93.75, 125 mg/mL
- Amount of vehicle (if gavage): 4 mL/kg
- Lot/batch no. (if required): MKCD1021
- Purity: not specified

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

A dose formulation analysis was not performed in this study.

Duration of treatment / exposure:

14 days

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

Doses / concentrations 4

Dose / conc.:

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

Doses / concentrations 5

Dose / conc.:

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

Doses / concentrations 6

Dose / conc.:

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

No. of animals per sex per dose:

24 animals (12 males and 12 females) were used for the study (2 male and 2 female animals per group).

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The doses for the first dose group and the control group were selected in consultation with the sponsor prior to the start of the study. The remaining doses were selected sequentially in consultation with the sponsor during the course of the treatment period of this study
- Rationale for animal assignment (if not random): random
- Fasting period before blood sampling for clinical biochemistry: overnight fasting
- Rationale for selecting satellite groups: not applicable
- Post-exposure recovery period in satellite groups: not applicable
- Section schedule rationale (if not random): random

Positive control:

not used

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily all animals were observed for morbidity and mortality except on weekends and public holidays when observations were made once daily.
- Cage side observations checked in included: morbidity and mortality

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: General clinical observations were made at least once a day, approximately at the same time each day and considering the peak period of anticipated effects after dosing.
- Cage side observations checked in included: The health condition of the animals was recorded.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weight was recorded once before assignment to the experimental groups and on study days 1, 3, 6, 8, 11 and 14 during the treatment period as well as on the day of necropsy.

FOOD CONSUMPTION:
- Time schedule for examinations: Food consumption was measured on study days 1, 8 and 14 for each cage.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

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

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: before necropsy
- Anaesthetic used for blood collection: No
- Animals fasted: Yes
- How many animals: all animals
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: before necropsy
- Animals fasted: Yes
- How many animals: all animals
- Parameters checked in table [No.1] were examined.

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

IMMUNOLOGY: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table No 2)

HISTOPATHOLOGY: Yes (see table No 2)

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Treatment with dichloro(methyl)phenylsilane caused adverse clinical signs in males and females of group 6 (500 mg/kg bw/day).
Male no. 11 of group 6 (500 mg/kg bw/day) which was euthanized for animal welfare reasons showed the clinical signs of moving the bedding, increased salivation (moderate), prone position, abnormal breathing, reduced spontaneous activity, slow movements, wasp waist (slight) and dehydration on treatment day 5.
Male no. 12 of group 6 (500 mg/kg bw/day) which was euthanized for animal welfare reasons showed the clinical signs of moving the bedding, increased salivation (moderate), abnormal breathing, slight reduced spontaneous activity and hypothermia on treatment day 2.
Female no. 23 of group 6 (500 mg/kg bw/day) which was euthanized for animal welfare reasons showed the clinical signs of moderate piloerection, apathy, severe reduced spontaneous activity, both eyelids closed and hypothermia on treatment day 4. This animal showed moving the bedding and slight reduced spontaneous activity during the treatment day 1-3.
Female no. 24 of group 6 (500 mg/kg bw/day) which was euthanized for animal welfare reasons showed the clinical signs of moderate piloerection, slight reduced spontaneous activity, dehydration, abnormal breathing and hypothermia on treatment day 3. This animal showed moving the bedding during the treatment day 1-2.
Male no. 9 of group 5 (375 mg/kg bw/day) which was euthanized for animal welfare reasons showed the clinical signs of increased salivation (slight to moderate), apathy, prone position, abnormal breathing, nasal discharge, moderate reduced spontaneous activity, both eyelids closed, lack of defecation, lacrimation, hypothermia, wasp waist (moderate), moderate piloerection, slow movements and dehydration on treatment day 8.
Female no. 22 of group 5 (375 mg/kg bw/day) which showed moving the bedding during day 7-10 and was found dead on treatment day 11.
There were no adverse clinical signs in group 2 (50 mg/kg bw/day), group 3 (100 mg/kg bw/day) and group 4 (250 mg/kg bw/day).
There were no clinical signs at 50 mg/kg bw/day of group 2 during the entire treatment period in both male and female.
Moving the bedding and slight to moderate salivations was transiently observed in all male and female animals of group 3-4 (100-250 mg/kg bw/day). This is assumed to be due to discomfort caused by a local reaction to Dichloro(methyl)phenylsilane.
The slight clinical sign of a hairless skin area (left forepaw) was observed in female no. 18 of group 3 (100 mg/kg bw/day) and female no. 20 of group 4 (250 mg/kg bw/day), however, this finding was not considered toxicologically relevant.

Mortality:

mortality observed, treatment-related

Description (incidence):

During the treatment period of this study, 2/2 males and 2/2 females of group 6 (500 mg/kg bw/day) and 1/2 males at 375 mg/kg bw/day were euthanized in a moribund condition due to animal welfare reasons. One rat at 375 mg/kg bw/day (female no. 22) was found dead on treatment day 11. Inflammatory lesions of the stomach were considered to be the cause of mortality. All remaining animals survived until the scheduled sacrifice.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Males of the control, group 2 (50 mg/kg bw/day), group 3 (100 mg/kg bw/day) and group 4 (250 mg/kg bw/day) tended to gain body weight throughout the study period. Males of group 5 (375 mg/kg bw/day) and group 6 (500 mg/kg bw/day) showed a tendency towards a loss of body weight. Body weight change of test item-treated females showed no trend towards body weight loss.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Mean food consumption from treatment day 1 to 14 was shown to be comparable up to 250 mg/kg bw/day when compared to control both in male and female. Food consumption of males and females at 375 mg/kg bw/day was slightly lower when compared to control. Food consumption was not reported for 500 mg/kg bw/day (group 6) in both male and female, since those rats were euthanized due to animal welfare reasons.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

No dose-dependent effect on haematology parameters of males and females in any of the test item-treated groups.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No effects on parameters of clinical biochemistry of males and females in any of the test item-treated groups which were considered toxicologically relevant. Slight differences between test item-treated males or females and corresponding controls followed no dose-dependency or consistency between the genders and thus were not considered toxicologically relevant.
Mean ALAT level was slightly lower in males of group 3 (100 mg/kg bw/day, deviation from control: 20 %). Mean Creatinine level was slightly lower in males of group 2 (50 mg/kg bw/day, deviation from control: 21 %), group 3 (100 mg/kg bw/day, deviation from control: 25 %) and group 4 (250 mg/kg bw/day, deviation from control: 39 %) and slightly higher in group 4 female (250 mg/kg bw/day, deviation from control: 26%).
Mean ASAT level was slightly lower in males of group 2 (50 mg/kg bw/day, deviation from control: 26 %), group 3 (100 mg/kg bw/day, deviation from control: 16 %) and group 4 (250 mg/kg bw/day, deviation from control: 25 %).
Mean AP level was moderately higher in females of group 4 (250 mg/kg bw/day, deviation from control: 87 %), this could be due to higher individual value of female no. 19 (136.85 U/L).
Mean K level was moderately higher in females of group 4 (250 mg/kg bw/day, deviation from control: 77 %), this could be due to higher individual value of female no. 19 (7.48 mmol/L).
Mean Cholesterol level was slightly lower in females of group 2 (50 mg/kg bw/day, deviation from control: 19 %), group 3 (100 mg/kg bw/day, deviation from control: 16 %) and higher in group 4 (250 mg/kg bw/day, deviation from control: 60 %).
Mean Urea level was slightly higher in females of group 2 (50 mg/kg bw/day, deviation from control: 12 %), group 3 (100 mg/kg bw/day, deviation from control: 11 %) and higher in group 4 (250 mg/kg bw/day, deviation from control: 23 %).

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Mean organ weights showed no dose-dependent differences between males and females treated with the test item and the respective control group. Organ weights from only one animal per sex were available from group 5 (375 mg/kg bw/day) as one male and one female rat were sacrificed due to animal welfare reasons prior to the scheduled sacrifice date.
Differences between test item-treated females and control animals in mean weight of uterus and ovaries were not considered toxicologically relevant as female reproductive organs undergo variable changes depending on the stage of the estrous cycle.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Test item-related gross lesions were noted in the stomach, small and large intestine
at ≥ 250 mg/kg bw/day. Gross lesions in the stomach are consisting of masses, adhesions, abnormal surface, hemorrhage, abnormal color or discolored foci and enlargement. In groups 5 (375 mg/kg bw/day) and 6 (500 mg/kg bw/day), there were changes (discoloration) in the duodenum and/or jejunum, and several cases of enlarged and/or abnormally colored adrenal glands, and single cases of spleen adhesion and abnormal discoloration of lung.

Neuropathological findings:

not examined

Description (incidence and severity):

Inflammatory and degenerative findings were seen in the stomach from animals at 50 mg/kg bw/day onwards. These findings consisted at 50 mg/kg bw/day of inflammations in the forestomach submucosa and one case of forestomach ulceration. In addition, there were single cases of inflammation in the serosa (i.e., peritonitis), and reactive changes in form of epithelial hyperplasia in the forestomach and increased hyperkeratosis of the forestomach epithelium in single cases.
At 100 mg/kg bw/day, the findings were similar but, in addition, there were single cases of minimal glandular stomach inflammation, degeneration of mucosal neck cells, and single cell necrosis of glandular mucosa cells. In groups 4 to 6 (250, 375 or 500 mg/kg), the aforementioned findings increased in incidence and severity.
In groups 5 and 6 (375 or 500 mg/kg), there were additional findings, i.e., degeneration of the forestomach epithelium, and glandular stomach erosion and ulceration. These findings caused in groups 5 and 6 animals the early death in one animal per sex from group 5, and in all group 6 animals. Inflammation and/or erosion were noted in single animals from groups 5 and 6, whereby the small intestine was involved at all segments.
Other related findings due to regurgitation consisted in the esophagus of keratin desquamation of in one male and both females of group 6, single cases of larynx necrosis and inflammation in one group 6 male, inflammatory secretion in the nasal cavities from one group 6 female, and aspiration pneumonia in one group 5 female. In addition, in one group 5 male, the adhesion of the spleen was due to subcapsular inflammation. Gross lesions, enlargement of the adrenal glands were histologically due to diffuse hypertrophy of the zona fasciculata. The later finding is deemed to be stress-related.

Histopathological findings: neoplastic:

not examined

Other effects:

not specified

Effect levels

1

Dose descriptor:

NOAEL

Remarks:

not determined

2

Dose descriptor:

LOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

gross pathology

histopathology: non-neoplastic

mortality

Target system / organ toxicity

Critical effects observed:

yes

Lowest effective dose / conc.:

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

System:

gastrointestinal tract

Organ:

intestine

stomach

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Applicant's summary and conclusion

Conclusions:

In the dose range-finding study, which was not conducted according to a guideline or GLP, no NOAEL was concluded. In the study test item-related gross lesions were noted in the stomach, small and large intestine at ≥ 250 mg/kg bw/day and these were evident during histopathological examination. At the microscopic examination, specific findings were found, starting at the dose of 50 mg/kg bw/day. These findings included inflammatory and degenerative lesions which consisted of erosions, inflammation, hyperplasia, ulceration, hyperkeratosis, single cell necrosis and epithelial degeneration.