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Toxicity to reproduction

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Administrative data

Endpoint:
screening for reproductive / developmental toxicity
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
19.11.2003 to 19.05.2005
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)
Qualifier:
according to guideline
Guideline:
other: USEPA OPPTS 870.3650
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: No data
- Age at study initiation: Nine weeks
- Weight at study initiation: Males: 294.2-351.5; Females: 200.2-260.2 g
- Fasting period before study: None
- Housing: individually housed in suspended wire-mesh cages (pregnant rats in shoebox cages)
- Diet (e.g. ad libitum): Ad libitum (except during FOB)
- Water (e.g. ad libitum): Ad libitum (except during FOB)
- Acclimation period: Six days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.2-22.5
- Humidity (%): 36.0-62.0
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 09.02.2004 To: 19.04.2005

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Conducted over nitrogen atmopshere. Test substance was placed into a volumetric flask and corn oil added to achieve the desired volume. The weight of the test substance added to the flask was used to calculate nominal dose solution concentrations. Dosing solutions were prepared at least once every two weeks consistent with the previously determined 15-day stability. The concentration, homogeneity and stability of the test substance in vehicle for at least 15 days.

VEHICLE
- Justification for use and choice of vehicle (if other than water): No data
- Concentration in vehicle: Various
- Amount of vehicle (if gavage): Up to 3 ml/kg
- Lot/batch no. (if required): 122K0131
- Purity: Considered 100%
Details on mating procedure:
A 1:1 mating ratio was used. After dosing on study day 14, the animals were paired by placing the lowest numbered ear tag reproductive group female within each group in the home cage of the male with the lowest numbered ear tag from the same group. Female animals were housed continuously with the same male until evidence of copulation was obtained. Females were evaluated daily for evidence of copulation, as indicated by either a vaginal copulatory plug or sperm in the vaginal smear. Day 0 of gestation was defined as the day evidence of copulation was obtained, at which time the female was returned to her home cage (shoebox cage).
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The concentration of methyltrimethoxysilane (MTMS) in corn oil dosing solutions was determined prior to the beginning of the definitive study.
Duration of treatment / exposure:
Toxicity group females and males were treated for 28 and 29 days, respectively. Reproductive group females were treated for 14 days prior to the mating period, during the mating period, and then up to and including post partum day 3, for a total of up to 51 days.
Frequency of treatment:
Daily, seven days/week
Details on study schedule:
No further relevant details.
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
corn oil
Dose / conc.:
50 mg/kg bw/day (actual dose received)
Dose / conc.:
250 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Based on a range-finding study

Examinations

Parental animals: Observations and examinations:
Mortality/Morbidity: Animals were observed at least twice daily in their cages for moribundity and mortality throughout the in-life phase of the study.
Clinical observations:
Daily Observations: General clinical examinations were made at least once a day and were conducted immediately after dosing. The examinations included, but were not limited to, changes in the skin, fur, eyes, mucous membranes, respiratory, circulatory, autonomic and central nervous system functions, motor activity and behavior patterns. Findings were recorded for individual animals. General clinical examinations were not performed on days when detailed physical examinations were performed.
Detailed Physical Examinations: All animals received a detailed physical examination once before the first dose administration (to allow for within-subject comparisons), and weekly thereafter. Examinations were made outside the home cage in a standard arena at approximately the same time each day. Observations were detailed and carefully recorded. Examinations included, but were not limited to, changes in skin, fur eyes, mucous membranes, occurrence of secretions and excretions, and autonomic activity. Changes in gait, posture and response to handling as well as the presence of clonic or tonic movement, stereotypies, difficult or prolonged parturition or bizarre behavior were recorded. The presence or absence of findings was recorded for individual animals.

Body weights and food consumption were recorded weekly. Additional body weights for reproductive group females were obtained on gestational day 0, 7, 14, and 20, and within 24 hours of parturition, and on postnatal day 4. Individual food consumption was determined for each group following group specific schedules. In addition, detailed clinical observations (functional observational battery [FOB] conducted out of the home cage) and locomotor activity were evaluated for all adult male and toxicity phase females once prior to the start of test article administration (baseline evaluations) and again during the last week of the test article administration. Blood samples were collected from males and toxicity group females on the day of scheduled termination for analysis of hematology and serum chemistry parameters.
Litter observations:
All reproductive phase females were allowed to deliver and rear their offspring to lactation day 4; surviving dams and pups were euthanized and examined on lactation day 4.On the day parturition was initiated (PND 0), the pups were sexed and examined for gross malformations, and the numbers of still born and live pups were recorded. Individual gestation length was calculated using the date delivery started. Abnormal behavior of the offspring was recorded. The dam and litter remained together until PND 4.

Mean measured parameters were calculated for:
Days of gestation
Undetermined sex
Male pups/litter
Female pups/litter
Males/Females per litter
Total pups/litter
Viable (live) pups/litter
Viable/Total pups per litter

Initial litter weight at parturition (g)
Initial average pup weight at parturition (g)
Final litter weight at PND 4 (g)
Final average pup weight at PND 4 (g)

Total number of implants
Corpora counts
Postmortem examinations (parental animals):
Clinical pathology assessments (hematology and serum chemistry) and macroscopic and microscopic examinations (including organ weights) were also performed on the appropriate groups of adult males and toxicity phase females. For females that delivered or had macroscopic evidence of implantation, the numbers of former implantation sites and corpora lutea were recorded. Recognizable fetuses for the females euthanized in extremis were examined externally and preserved in 10% neutral-buffered formalin. For females that failed to deliver, a pregnancy status was determined. Uteri with no macroscopic evidence of implantation were opened and subsequently placed in a 10% ammonium sulfide solution for detection of early implantation loss.
Postmortem examinations (offspring):
Intact offspring dying from PND 0 to 4 were necropsied. Cannibalized pups were discarded without necropsy. Tissues were preserved in 10% neutral-buffered formalin for possible future histopathologic examination only as deemed necessary by gross findings. The carcass of each pup was then discarded.
Statistics:
Reproductive parameters with the exception of litter size were analyzed using an ANCOVA (Analysis of Covariance) with liter size as the covariate. Litter size was analyzed using an ANOVA.
Reproductive indices:
Male (Female) Mating Index (%)
Male Fertility Index (%)
Male Copulation Index (%)
Female Fertility Index (%)
Female Conception Index (%)
Offspring viability indices:
On the day parturition was initiated (PND 0), the pups were sexed and examined for gross malformations, and the numbers of still born and live pups were recorded.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Thirty percent of the animals in the 50 mg/kg bw/day dose group and 100 % of the animals in the 250 and 1000 mg/kg bw/day dose groups exhibited a transient period of salivation and/or abnormal inactivity at least once over the course of treatment immediately after dosing.
Mortality:
mortality observed, treatment-related
Description (incidence):
There were two unscheduled deaths (one female each at 0 and 50 mg/kg  bw/day); both were related to dosing errors.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Statistically significant decreases in body weight gain and food consumption were noted for 1000 mg/kg bw/day group males. 
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
No statistically significant differences in treatment group maternal food consumption relative to control group animals.
Food efficiency:
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
A marked increase in prothrombin time was observed for males at 250 and 1000 mg/kg bw/day whereas females were unaffected. Exposure was also associated with increased blood platelet concentration for males and females, and increased red blood cell concentration in males at 1000 mg/kg bw/day.
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Exposure to MTMS was associated with organ weight and/or histomorphological changes in males (liver, thymus, thyroid, duodenum, jejunum) and females (liver, thyroid, duodenum, jejunum, and adrenal gland) at dose levels at or above 250 mg/kg bw/day.  

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
no effects observed
Description (incidence and severity):
No treatment-related effects were observed in any of the reproductive parameters evaluated. All females bred successfully and delivered live litters. 

Details on results (P0)

"Number pregnant per dose level: 10
"Number aborting: 0
"Number of resorptions, early/late if available: None detected.
"Number of implantations: Group Mean (standard deviation) Control: 15 (2.2); 50 mg/kg: 16 (2.0); 250 mg/kg: 16 (1.4); 1000 mg/kg: 16 (1.9)
"Number of corpora lutea: Group Mean (standard deviation)
Control: 19(4.7); 50 mg/kg: 19(3.1); 250 mg/kg:18(2.0); 1000 mg/kg: 17(3.9)
"Duration of Pregnancy: Group Mean (standard deviation)
Control: 21 (0.5); 50 mg/kg: 21(0.5); 250 mg/kg: 22(0.5); 1000 mg/kg: 22(0.5)

Effect levels (P0)

Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No reproductive effects at the highest dose tested.

Target system / organ toxicity (P0)

Critical effects observed:
no

Results: F1 generation

General toxicity (F1)

Clinical signs:
no effects observed
Mortality / viability:
no mortality observed
Body weight and weight changes:
no effects observed
Food efficiency:
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings:
not examined

Developmental neurotoxicity (F1)

Behaviour (functional findings):
not examined

Developmental immunotoxicity (F1)

Developmental immunotoxicity:
not examined

Details on results (F1)

No gross abnormalities were found for any of the pups, with the exception of a single runt in the 50 mg/kg bw/day group.

Effect levels (F1)

Dose descriptor:
NOAEL
Generation:
F1
Effect level:
>= 1 000 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No effects at the highest dose tested.

Target system / organ toxicity (F1)

Critical effects observed:
no

Overall reproductive toxicity

Reproductive effects observed:
no

Applicant's summary and conclusion

Conclusions:
In the oral Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test with trimethoxy(methyl)silane (CAS 1185-55-3), conducted according to OECD Test Guideline 422 and in compliance with GLP, the concluded NOAEL for reproductive toxicity was at least 1000 mg/kg bw/day.