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Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2004-09-06 to 2004-10-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report date:
2005

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Version / remarks:
1996
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: USEPA OPPTS 870.3650
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
3-(triethoxysilyl)propiononitrile
EC Number:
213-050-5
EC Name:
3-(triethoxysilyl)propiononitrile
Cas Number:
919-31-3
Molecular formula:
C9H19NO3Si
IUPAC Name:
3-(triethoxysilyl)propanenitrile

Test animals

Species:
rat
Strain:
Wistar
Details on species / strain selection:
HanBrl:WIST (SPF)
Sex:
male/female
Details on test animals or test system and environmental conditions:
Rats were obtained from RCC Ltd Laboratory Animal Services, Fullinsdorf, Switzerland.
Animals were a minimum of 8 weeks of age at delivery. Males were 227-271 grams and females were 165-216 grams. Animals were acclimated for 7 days prior to pairing, under test conditions with an evaluation of the health status. Animals rooms were air conditioned with 10-15 air changes per hour; the environment was monitored continously with recordings of temperature and relative humidity, 12 hours artificial fluorescent light/12 hours dark with background music played at a centrally defined low volume for at least 8 hours during the light period. Animals were housed in Makrolon (R) cages with wire mesh tops and standard granulated softwood bedding. Pelleted standard rat/mouse maintenance diet was available ad libitum. Tap water from Fullinsdorf in bottles was available ad libitum.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
The test item was administered once daily, by gavage. All animals received a dose volume of 2 mL/kg body weight with a daily adjustment of the individual volume to the actual body weight. Control animals were dosed with the vehicle alone (dried corn oil)
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Samples for determination of actual test item concentrations, stability (7 day) and homogeneity in the prepared mixtures were taken on the first day of preparation. Samples for determination of actual test item concentrations and homogeneity were also taken on one occasion during the gestation period. Analysis were performed using a Gas Chromatographic method.
Duration of treatment / exposure:
Males and toxicity group females: at least 28 days; Reproductive group females: throughout the pre-pairing (14 day), pairing and gestation periods until day 3 of lactation
Frequency of treatment:
daily
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
Group 1
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Remarks:
Group 2
Dose / conc.:
500 mg/kg bw/day (actual dose received)
Remarks:
Group 3
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
Remarks:
Group 4
No. of animals per sex per dose:
10 males/20 females/group
Control animals:
yes, concurrent vehicle
Details on study design:
3-(Triethoxysilyl)propiononitrile was administered once daily orally (by gavage) to 10 males and 20  female (10 toxicity group and 10 reproductive group females) rats at  doses of 100, 500 and 1000 mg/kg bw/day. A concurrent vehicle control  group (dried corn oil) was also included.  Males and toxicity group  females were sacrificed after they had been treated for at least 28 days; reproductive group females were dosed  throughout the prepairing (14 day), pairing and gestation periods until day 3 of lactation up to a maximum of 44 days; reproductive group females and pups were sacrificed on day 4 of lactation.

Examinations

Observations and examinations performed and frequency:
All animals were observed at least twice daily to assess external condition, behavior and mortality/morbidity.  Detailed clinical observations were conducted outside the home cage once prior to the first test item administration and weekly thereafter. The FOB evaluation was performed on all adult males and all toxicity group females prior to the start of dosing and during the last week of dosing. Body weights and food consumption were recorded weekly. From all males and all toxicity group females, blood samples were obtained on the day of scheduled necropsy for hematology and clinical chemistry parameters evaluations. 
Sacrifice and pathology:
Organs examined at necropsy (macroscopic and microscopic):  Animals were subjected to a complete gross necropsy that included examination of the cranial, thoracic, and abdominal cavities and their contents. Tissues and organs were collected for histological examination. The following organs were collected for males and females and weighed: adrenals, brain, heart, kidneys, liver, lungs, spleen, thymus, uterus, ovaries, testes, prostate, seminal vesicles and epididymides.
Statistics:
Statistical Methods: Mean and standard deviation of data were calculated. Univariate one-way analysis of variance was used to assess the significance of intergroup differences. Dunnett t-test, based on a pooled variance estimate, was used for intergroup comparisons. The Steel test (rank test) was applied when the data could not be assumed  to follow a normal distribution. Fisher's Exact test for 2x2 tables was applied if the variables could be dichotomized without loss of information. Quantitative data were used by a one-way analysis of variance (ANOVA) when the variance were considered homogeneous according to Bartlett. Alternatively, if the variances were considered to be heterogeneous, a non-parametric Kruskal-Wallis was used. Treated groups were then compared to the controgroups using Dunnett test. Statistically significant probabilities are reported at either the p<0.05 or p<0.01 levels.

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):
no effects observed
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Slightly reduced levels in the erythrocyte count, hemoglobin concentration and hematocrit was observed in both sexes at 1000 mg/kg bw/day.
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
In males, increased absolute and/or relative organ weight were noted for the following organs: heart (500 and 1000 mg/kg bw/day), liver (100, 500 and 1000 mg/kg bw/day), kidneys (500 and 1000 mg/kg bw/day) and spleen (1000 mg/kg bw/day)
In females, at 1000 mg/kg bw/day, increased absolute and/or relative organs weight were noted for the following organs: kidneys and spleen
These findings correlated with the findings at histopathological examination, where severe renal changes were noted. The change in mean spleen weight was considered to be secondary to these changes.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
At 1000 mg/kg bw/day, macroscopic renal changes were noted for three males and thickened liver was noted for one male. At 1000 mg/kg bw/day, macroscopic renal changes were noted for three toxicity group females. These findings were considered to be test-item related since they correlated with histopathological findings.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
At 1000 and 500 mg/kg bw/day, chronic tubular lesions of minimal to moderate severity was observed in animals of either sex, correlating with macroscopic renal discoloration and foci and increased kidney weights recorded at necropsy. Males were more severely affected than females. Hyperplasia of transitional cell epithelium of the renal pelvis was seen at 500 and 1000 mg/kg bw/day in either sex, mostly in conjunction with chronic tubular lesions. Further, renal pyelonephritis and increased incidence of splenic extramedullary hematopoiesis (males only) were present in treated animals and were considered secondary to the primary renal tubular lesion.
No test item-related histopathological findings were noted in the reproductive organs of either sex. In particular, the assessment of the integrity of the spermatogenetic cycle did not reveal any evidence of impaired spermatogenesis.
Histopathological findings: neoplastic:
no effects observed
Other effects:
not specified
Details on results:
Oral administration of 3-(triethoxysilyl)propiononitrile to male and toxicity group female rats at concentrations of 1000 mg/kg/day for 28 consecutive days was generally well tolerated. No effects were observed in the body weight and food consumption. 
None of the parameters under investigation during the Functional Observational Battery (FOB) gave any indication of treatment-related effects.

Increased organ weights (kidneys, spleen, heart and liver in  males; kidneys and spleen in toxicity group females), slight reduction in red cell count (not statistically significant), hemoglobin concentration and hematocrit in males and toxicity group females and histopathological changes in kidneys (chronic tubular lesions of minimal to moderate severity with minimal to slight hyperplasia of the renal pelvis epithelium [related to tubular damage] and renal pyelonephritis) were noted in males and toxicity group females dosed at 1000 mg/kg bw/day.
Administration of 500 mg/kg bw/day resulted in increased organ weights (kidneys, heart and liver in males only) and histopathological changes in kidneys including chronic tubular lesions with minimal to slight hyperplasia of the renal pelvis epithelium (isolated) and renal pyelonephritis (males and toxicity group females) and spleen including extramedullary hematopoiesis (males only).
Administration of 100 mg/kg bw/day resulted in increased liver weight in males. In the absence of a histopathologic correlation the increased liver weight was considered most probably of adaptive nature and therefore of no adverse character.   
Based on these data, the No Observed Adverse Effect Level (NOAEL) for toxicity of 3-(triethoxysilyl)propiononitrile was considered to be 100 mg/kg bw/day.

Effect levels

Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
organ weights and organ / body weight ratios

Target system / organ toxicity

Critical effects observed:
yes
Lowest effective dose / conc.:
500 mg/kg bw/day (actual dose received)
System:
urinary
Organ:
kidney
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
not specified

Any other information on results incl. tables

ABSOLUTE MEAN LIVER WEIGHT in grams (St. Dev.):
Males:
0 mg/kg bw/day: 9.40 (0.52)
100 mg/kg bw/day: 10.25 (0.93)
500 mg/kg bw/day: 10.33* (0.73)
1000 mg/kg bw/day: 10.26 (1.03)

Toxicity group females:
0 mg/kg bw/day: 6.31 (0.48)
100 mg/kg bw/day: 6.05 (0.51)
500 mg/kg bw/day: 6.26 (0.46)
1000 mg/kg bw/day: 6.76 (0.50)

RELATIVE MEAN LIVER/BODY WEIGHT in grams (St. Dev.):
Males:
0 mg/kg bw/day: 2.66 (0.12)
100 mg/kg bw/day: 2.86 (0.19)
500 mg/kg bw/day: 2.98** (0.13)
1000 mg/kg bw/day: 2.95** (0.23)

Toxicity group females:
0 mg/kg bw/day: 2.91 (0.27)
100 mg/kg bw/day: 2.80 (0.23)
500 mg/kg bw/day: 2.89 (0.20)
1000 mg/kg bw/day: 3.13 (0.14)

RELATIVE MEAN LIVER/BRAIN WEIGHT in grams (St. Dev.):
Males:
0 mg/kg bw/day: 464.83 (31.38)
100 mg/kg bw/day: 510.76* (43.28)
500 mg/kg bw/day: 519.72* (32.61)
1000 mg/kg bw/day: 507.52 (52.15)

Toxicity group females:
0 mg/kg bw/day: 334.47 (18.01)
100 mg/kg bw/day: 329.74 (35.48)
500 mg/kg bw/day: 339.49 (20.97)
1000 mg/kg bw/day: 358.50 (22.19)

Where:
*/**: Dunnett-test based on pooled variance sig. at 5% or 1% level,  respectively.

Applicant's summary and conclusion

Conclusions:
In a repeated dose oral toxicity test with the reproduction/developmental toxicity screening test with the registered substance 3-(triethoxysilyl)propiononitrile, conducted according to OECD Test Guideline 422 and in compliance with GLP, a NOAEL for systemic effects was concluded to be 100 mg/kg bw/day (nominal) based on increased organ weights and kidney effects at the 500 mg/kg bw/day (nominal) dose.