Triethoxy(3-thiocyanatopropyl)silane

Endpoint summary

Description of key information

In the key study conducted according to OECD Test Guideline 408 and in compliance with GLP (Charles River Laboratories, 2022, reliability score 1), Wistar Han rats were administered triethoxy(3-thiocyanatopropyl)silane (CAS No. 34708-08-2, EC No. 252-161-3) at 0, 30, 100, and 300 mg/kg bw/day via oral gavage (arachis oil vehicle) for 7 days/week over 13 weeks. The systemic NOAEL for triethoxy(3-thiocyanatopropyl)silane was 100 mg/kg bw/day, based on effects in males (decreased body weight, body weight gain, and food consumption) and females (increased renal organ weight and related histopathological alterations) at 300 mg/kg bw/day. For local effects in the non-glandular stomach, the NOAEL was 30 mg/kg bw/day.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2020/07/01 - 2021/02/01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Species:

rat

Strain:

Wistar

Remarks:

Crl: WI(Han)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Deutschland, Sulzfeld, Germany
- Females: Based on age, nulliparous and non-pregnant
- Age at study initiation: 6-7 weeks
- Weight at study initiation: Males weighed 153-206 g and females weighed 88-153 g
- Fasting period before study: No
- Housing: Up to 5 animals of same sex / dose group, in Polycarbonate cages (Makrolon type IV or Makrolon type 2000P)
- Diet: SM R/M-Z from SSNIFF, ad libitum
- Water: Municipal tap water, ad libitum
- Acclimation period: At least 5 days

DETAILS OF FOOD AND WATER QUALITY:
- Diet: Results of analysis for nutritional components and environmental contaminants were provided by the supplier and are on file at the Test Facility. It is considered that there were no known contaminants in the feed that would interfere with the objectives of the study.
- Water: Periodic analysis of the water was performed, and results of these analyses are on file at the Test Facility. It is considered that there were no known contaminants in the water that could interfere with the outcome of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-22
- Humidity (%): 46-77
- Air changes (per hr): 10 or more
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 2020/07/28 (initiation of dosing) To: 2020/11/25

Route of administration:

oral: gavage

Vehicle:

arachis oil

Remarks:

Dried and deacidified arachis oil, specific gravity 0.885

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Test item dosing formulations (w/w) were homogenized to visually acceptable levels at appropriate concentrations to meet dose level requirements. The dosing formulations were prepared daily as a solution and dosed within 6 hours after preparation of the formulation.

No adjustment was made for specific gravity of the test item. No correction was made for the purity/composition of the test item.

Test item dosing formulations were kept at room temperature until dosing. If practically possible, the dosing formulations and vehicle were continuously stirred until and during dosing.

VEHICLE
- Justification for use and choice of vehicle: Trial preparations were performed to establish a suitable formulation procedure, not part of this study
- Concentration in vehicle: 0, 7.5, 25, 75 mg/mL
- Amount of vehicle: Dosing solution volume, 4 mL/kg bw
- Lot/batch no.: 1911106
- Purity: Not specified

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Dose formulation samples were collected in weeks 1, 6 and 12, with analysis performed using a validated analytical procedure to assess concentration and homogeneity

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

7 d/wk

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

No. of animals per sex per dose:

10M/10F in main design (all dose levels), 5M/5F for recovery groups (0, 300 mg/kg bw/day groups)

Control animals:

yes

Details on study design:

- Dose selection rationale: Results of the dose range finding study
- Rationale for animal assignment: Random
- Fasting period before blood sampling for clinical biochemistry: Yes, overnight with a maximum of 24 hours
- Rationale for selecting satellite groups: To assess recovery from or delayed toxicity
- Post-exposure recovery period in satellite groups: 28 days
- Section schedule rationale: Not specified

Observations and examinations performed and frequency:

MORTALITY: Yes
All animals, at least twice daily beginning upon arrival through termination.

CAGE SIDE OBSERVATIONS: Yes
All main study and recovery animals, at least twice daily. From Day 1, 0-15 minutes post dose, and 45-75 minutes post dose.

DETAILED CLINICAL OBSERVATIONS: Yes
All main study and recovery animals, once pretreatment and weekly during treatment and recovery periods; and on the day of necropsy.

BODY WEIGHT: Yes
All main study and recovery animals, weekly from at least Day 1 and throughout the study.

FOOD CONSUMPTION Yes
All main study and recovery animals, weekly from at least Day 1 and throughout the study, quantitative per cage.

FOOD EFFICIENCY: No

WATER CONSUMPTION: Yes
All main study and recovery animals, regular basis throughout the study, visual inspection of water bottles.

OPHTHALMOSCOPIC EXAMINATION: Yes
Pretreatment: All main study and recovery animals once (including spare animals). Dosing Period: All 0 and 300 mg/kg bw/day animals during Week 13.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At end of treatment period
- Anaesthetic used for blood collection: Yes, isoflurane
- Animals fasted: Yes, overnight with a maximum of 24 hours
- How many animals: All main study and recovery animals
- See Table 1 below for list of analyzed parameters

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At end of treatment period
- Animals fasted: Yes, overnight with a maximum of 24 hours
- How many animals: All main study and recovery animals
- See Table 2 for list of analyzed clinical chemistry parameters.
- In addition, coagulation was assessed (prothrombin Time (PT) and activated partial thromboplastin time (APTT).

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Once during the Dosing Period. The first 5 animals per sex per group during Weeks 12-13
- Dose groups that were examined: All animals
- Battery of functions tested: hearing ability, pupillary reflex, static righting reflex, fore- and hind-limb grip strength, locomotor activity (total movements and ambulations)

IMMUNOLOGY: No

OTHER: ESTROUS STAGE DETERMINATION
All main study females, on the day of necropsy at end of treatment, vaginal smear to determine the stage of estrus. All recovery females, on the day of necropsy.

Sacrifice and pathology:

SACRIFICE:
Main study and recovery animals surviving until scheduled euthanasia were weighed, and euthanized using isoflurane, followed by exsanguination. Animals were fasted (overnight with a maximum of 24 hours) before their scheduled necropsy.

The terminal procedures are summarized in Table 3 below.

ORGAN WEIGHT: Yes
All main study and recovery animals.
- See Table 4 below for list weighed organs

GROSS PATHOLOGY: Yes
All main study and recovery animals, as follows:
- Full list of tissues
- See Tables 3 and 5 below for terminal procedures and full list of tissues collected

HISTOPATHOLOGY: Yes
All main study and recovery animals, as follows:
- 0 and 300 mg/kg bw/day dose groups: Full list of tissues
- 30 and 100 mg/kg bw/day dose groups: Gross lesions and target tissues
- Target tissues: Stomach and kidneys: All males and females in main study 30 and 100 mg/kg bw/day groups, and 0 and 300 mg/kg bw/day recovery groups. Thymus: All males in main study 30 and 100 mg/kg bw/day groups, and 0 and 300 mg/kg bw/day recovery groups.
- See Tables 3 and 5 below for terminal procedures and full list of tissues collected

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Hunched posture and/or erected fur were observed at 300 mg/kg bw/day in seven males, and in six females, between Days 2 and 92.

The other clinical findings including the above signs at 30 and 100 mg/kg bw/day were considered not toxicologically relevant.

Please see attached Summary Table 1 below.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Test item-related and adverse lower body weight and body weight gain in males at 300 mg/kg bw/day, which recovered during the dosing-free period.

Please see attached Summary Figure 1, and Summary Tables 2 and 3 below.

Food consumption and compound intake (if feeding study):

not specified

Description (incidence and severity):

Test item-related and adverse lower food consumption in males at 300 mg/kg bw/day, which partially recovered during the dosing-free period.

Please see attached Summary Figure 2 and Summary Table 4 below.

Food efficiency:

not examined

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

no effects observed

Description (incidence and severity):

Water consumption was monitored by visual inspection of the water bottles, results not reported.

Ophthalmological findings:

effects observed, non-treatment-related

Description (incidence and severity):

No ophthalmology findings were noted that were considered related to treatment with the test item. Nature and incidence of findings were within the range considered normal for rats of this age and strain.

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

At 300 mg/kg bw/day, increased reticulocyte counts were observed in males and females at the end of the dosing period. In addition, females at 300 mg/kg bw/day, showed increased counts of large unstained cells. Both findings normalized following the Recovery Period. In absence of a histopathological correlation, the findings at this dose level were considered not adverse.

Remaining findings were considered of no toxicological significance. No effects reported for 30 or 100 mg/kg bw/day.

Please see attached Summary Table 7 below.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Clinical chemistry findings at 100 and/or 300 mg/kg bw/day at the end of the Dosing Period were as follows:
- Increased calcium concentrations in males and females
- Decreased T4 and (at 300 mg/kg bw/day) increased TSH concentrations in males
- Decreased T3 and (at 100 mg/kg bw/day) T4 concentrations, and increased TSH concentrations in females
- Increased triglyceride concentrations (at 300 mg/kg bw/day) in males

There were no corresponding gross- or histopathology findings in the thyroid. In terms of the elevated calcium and triglyceride levels, see the renal histopathology results at 300 mg/kg bw/day as discussed below.

The above findings normalized following the Recovery Period. In absence of a histopathological correlation, the findings at these dose levels were considered not adverse.

Remaining findings were considered not test item-related. No effects reported for 30 mg/kg bw/day.

Please see attached Summary Table 9 below.

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

All findings were normal compared to controls (hearing ability, hearing ability, pupillary reflex, static righting reflex, male grip strength, female fore-leg grip strength, motor activity), or were considered not toxicologically relevant (female hind-leg grip strength at 100 and 300 mg/kg bw/day). Latter was within range considered normal for rats of this age and strain and lacked a clear dose-related response.

Please attached Summary Tables 5 and 6 below.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

At 300 mg/kg bw/day, test item-related lower absolute thymus weights in males, higher relative kidney weights in females and higher relative liver weights in males and females were observed.

Changes in kidney weight could be correlated with multifocal bilateral tubular basophilia with mononuclear cell infiltrates and showed no recovery following the treatment-free period. No microscopic correlates were observed for the changes in thymus and liver weights.

Some organ weight differences were statistically significant when compared to the control group but were considered to be the result of a test item-related effect on final body weight or due to a high physiological variability (uterus).

Please attached Summary Tables 10 and 11 below.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

LOCAL EFFECTS:
Test item-related macroscopic findings were present in the stomach of both sexes. Dark purple/red foci in the glandular stomach, dark grey/purple/red foci in the non-glandular stomach and/or an irregular surface of the non-glandular stomach was seen in one female at 30 mg/kg bw/day, six females at 100 mg/kg bw/day and five males and five females at 300 mg/kg bw/day at the End of Treatment. Microscopic correlates for the abnormalities in the non-glandular stomach consisted of hemorrhage and epithelial hyperplasia, respectively. In addition, two males at 300 mg/kg/day showed enlarged livers (no corresponding histopathology).

These findings were not seen at the end of recovery.

The remainder of the recorded macroscopic findings were within the range of background gross observations encountered in rats of this age and strain.

Please see attached Summary Table 12 below.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

SYSTEMIC EFFECTS:
Tubular basophilia and mononuclear cell infiltration were ascribed to treatment with the test item only when scored as bilateral and multifocal at 300 mg/kg bw/day. These findings correlated with increased kidney weight in females. These findings were recorded in females at the end of the Dosing Period as well as at the end of the recovery period at severities up to moderate degree and were regarded to be adverse. In the kidney, minimal tubular basophilia and mononuclear cell infiltration are common background pathology findings. Accumulation of hyaline droplets in the kidney in males was also seen, which showed full recovery at the end of the recovery period. Accumulation of hyaline droplets is caused by an increased production of alpha-2-urinary-globulin which is a protein specific for male rats. This is a well-known phenomenon and was in absence of indicators of tubular damage regarded to be non-adverse.

LOCAL EFFECTS:
Histopathological examination in animals treated at 300 mg//kg bw/day findings consisted of hemorrhage, epithelial hyperplasia, ulceration, mixed cell infiltration, edema and hyperkeratosis in the non-glandular stomach in males and females, which was regarded to be adverse. These findings correlated with macroscopically dark grey/purple/red and/or an irregular surface (considered non-adverse) at necropsy.

See attached Summary Table 13 below.

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Description (incidence and severity):

Coagulation parameters of treated rats were considered not affected by treatment up to 300 mg/kg bw/day. Please see attached Summary Table 8 below.

Estrous stage determined, results not reported.

Key result

Dose descriptor:

NOAEL

Remarks:

local effects

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

gross pathology

histopathology: non-neoplastic

Remarks on result:

other: Based on histopathology findings in the non-glandular stomach at 100 and 300 mg/kg bw/day, with corresponding gross pathology

Key result

Dose descriptor:

NOAEL

Remarks:

systemic effects

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Remarks on result:

other:

Remarks:

Based on effects in males (decreased body weight, body weight gain, and food consumption) and females (increased renal organ weight and related histopathological alterations) at 300 mg/kg bw/day.

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

300 mg/kg bw/day (nominal)

System:

urinary

Organ:

kidney

Treatment related:

yes

Dose response relationship:

no

Relevant for humans:

not specified

Conclusions:

In a study conducted according to OECD Test Guideline 408 and in compliance with GLP (reliability score 1), Wistar Han rats were administered triethoxy(3-thiocyanatopropyl)silane at 0, 30, 100, and 300 mg/kg bw/day via oral gavage (arachis oil vehicle) for 7 days/week over 13 weeks. The systemic NOAEL for triethoxy(3-thiocyanatopropyl)silane was 100 mg/kg bw/day, based on effects in males (decreased body weight, body weight gain, and food consumption) and females (increased renal organ weight and related histopathological alterations) at 300 mg/kg bw/day. For local effects in the non-glandular stomach, the NOAEL was 30 mg/kg bw/day.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

100 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

Klimisch score of 1, based on the repeated dose oral (reliability score 1) data for triethoxy(3-thiocyanatopropyl)silane

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Triethoxy(3-thiocyanatopropyl)silane has been evaluated in a study conducted according to OECD Test Guideline 408 and in compliance with GLP (Charles River Laboratories, 2022, reliability score 1). Wistar Han rats were administered triethoxy(3-thiocyanatopropyl)silane at 0, 30, 100, and 300 mg/kg bw/day via oral gavage (arachis oil vehicle) for 7 days/week over 13 weeks. The main study included 10 rats per sex per dose group, with 5 rats per sex in the 28-day recovery (0 and 500 mg/kg bw/day) groups. Observations and examinations were conducted per OECD Test Guideline 408, and included cage-side observations, detailed clinical signs, body weights, food consumption, ophthalmology, functional observation tests, oestrous stage determination, clinical pathology parameters (haematology, coagulation and clinical chemistry), organ weights, gross pathology, and histopathology.

 

No deaths occurred during the study. Clinical signs included hunched posture and/or erected fur at 300 mg/kg bw/day in seven males and six females, between Days 2 and 92. Other clinical findings were considered not toxicologically relevant.

 

Test item-related and adverse lower body weight and body weight gain occurred in males at 300 mg/kg bw/day, which recovered during the dosing-free period. Test item-related and adverse lower food consumption was also observed in males at 300 mg/kg bw/day, with this finding partially recovering during the dosing-free period.

 

No ophthalmology findings were noted that were considered related to treatment with the test item. The nature and incidence of findings were within the range considered normal for rats of this age and strain.

 

At 300 mg/kg bw/day, haematology effects (increased reticulocyte counts) were observed in males and females at the end of the dosing period. In addition, females at 300 mg/kg bw/day showed increased counts of large unstained cells. Both findings normalized following recovery. In absence of a histopathological correlation, the findings at this dose level were considered non-adverse. The remaining findings were considered of no toxicological significance. No effects were reported for 30 or 100 mg/kg bw/day.

 

Clinical chemistry findings at 100 and/or 300 mg/kg bw/day at the end of the dosing period were as follows:

- Increased calcium concentrations in males and females

- Decreased T4 and (at 300 mg/kg bw/day) increased TSH concentrations in males

- Decreased T3 and (at 100 mg/kg bw/day) T4 concentrations, and increased TSH concentrations in females

- Increased triglyceride concentrations (at 300 mg/kg bw/day) in males

 

There were no corresponding gross pathology or histopathology findings in the thyroid. In terms of the elevated triglyceride levels, see the renal histopathology results at 300 mg/kg bw/day discussed below.

 

All behavioural results were normal compared to controls (hearing ability, hearing ability, pupillary reflex, static righting reflex, male grip strength, female fore-leg grip strength, motor activity), or were considered not toxicologically relevant (female hind-leg grip strength at 100 and 300 mg/kg bw/day). Latter was within the range considered normal for rats of this age and strain and lacked a clear dose-related response.

 

For organ weights, test item-related lower absolute thymus weights in males, higher relative kidney weights in females and higher relative liver weights in males and females were observed at 300 mg/kg bw/day. Changes in female kidney weight could be correlated with multifocal bilateral tubular basophilia with mononuclear cell infiltrates and showed no recovery following the treatment-free period. No microscopic correlates were observed for the changes in thymus and liver weights.

 

Test item-related gross pathology was seen locally in the non-glandular stomach of both sexes, and in the liver for two males. Dark purple/red foci in the glandular stomach, dark grey/purple/red foci in the non-glandular stomach and/or an irregular surface of the non-glandular stomach was seen in one female at 30 mg/kg bw/day, six females at 100 mg/kg bw/day and five males and five females at 300 mg/kg bw/day at the end of treatment. Microscopic correlates for the abnormalities in the non-glandular stomach consisted of haemorrhage and epithelial hyperplasia, respectively. In addition, two males at 300 mg/kg bw/day showed enlarged livers (no corresponding histopathology). The non-glandular stomach and liver findings were not seen at the end of recovery. The remainder of the recorded macroscopic findings were within the range of background gross observations encountered in rats of this age and strain.

 

Upon histopathologic examination, both systemic and local findings were reported. In the kidney, tubular basophilia and mononuclear cell infiltration were ascribed to treatment with the test item only when scored as bilateral and multifocal at 300 mg/kg bw/day. These findings correlated with increased kidney weight in females. These findings were recorded in females at the end of the treatment as well as at the end of the recovery at severities up to a moderate degree and were regarded to be adverse. Minimal tubular basophilia and mononuclear cell infiltration are common background pathology findings in the rat kidney. Accumulation of hyaline droplets in the kidney in males also was seen in the study, which showed full recovery at the end of the recovery period. Accumulation of hyaline droplets is caused by an increased production of alpha-2-urinary-globulin which is a protein specific for male rats. This is a well-known phenomenon and in absence of indicators of tubular damage regarded to be non-adverse.

 

Locally in the non-glandular stomach, histopathological findings in animals treated at 300 mg//kg bw/day consisted of haemorrhage, epithelial hyperplasia, ulceration, mixed cell infiltration, oedema and hyperkeratosis in the non-glandular stomach in males and females, which was regarded to be adverse. These findings correlated with macroscopically dark grey/purple/red and/or an irregular surface (interpreted as non-adverse) at necropsy.

 

The systemic NOAEL for triethoxy(3-thiocyanatopropyl)silane was 100 mg/kg bw/day, based on effects in males (decreased body weight, body weight gain, and food consumption) and females (increased renal organ weight and related histopathological alterations) at 300 mg/kg bw/day. For local effects in the non-glandular stomach, the NOAEL was 30 mg/kg bw/day.

 

In a 14-day range finding study conducted in compliance with GLP (Charles River Laboratories, 2022, Appendix 3, reliability score 2), Wistar Han rats (3 per sex per dose group) were administered triethoxy(3-thiocyanatopropyl)silane at 0, 100, 300, and 500 mg/kg bw/day via daily oral gavage (arachis oil vehicle) for 14 days. These endpoints were assessed: mortality, cage side clinical signs, body weight, food consumption, and gross pathology. Except as noted in the study report, the test system, procedures and techniques were identical to those used during the main study. The systemic NOAEL for triethoxy(3-thiocyanatopropyl)silane was 100 mg/kg bw/day, based on clinical signs (prostrate, posture, gait, activity, erected fur, and/or salivation) in both sexes at 300 mg/kg bw/day. Mortality (1/3 males on Day 1) and additional clinical signs occurred at 500 mg/kg bw/day. For local effects in the non-glandular stomach, the NOAEL was 300 mg/kg bw/day, based on gross pathology at 500 mg/kg bw/day (blood analysis and histopathology not performed). The findings were used for dose selection for the main repeated dose study.

Justification for classification or non-classification

Based on the available information related to systemic toxicity, triethoxy(3-thiocyanatopropyl)silane does not require classification for repeated dose toxicity according to Regulation (EC) No, 1272/2008. Irritation effects were observed in the

non-glandular stomach, but this local finding does not trigger classification.