Registration Dossier

Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Justification for type of information:
Data is from peer-reviewed journal

Data source

Reference
Reference Type:
publication
Title:
Oral developmental toxicity study of test chemical in rats
Author:
B.A. Magnuson et.al.
Year:
2007
Bibliographic source:
Food and Chemical Toxicology 45 (2007)

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Principles of method if other than guideline:
The objective of the study was to determine the developmental toxicity potential of test chemical when administered orally to pregnant rats during the period of major organogenesis and histogenesis.
GLP compliance:
not specified
Limit test:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Dimethyl sulphone
- Molecular formula (if other than submission substance): C2H6O2S
- Molecular weight (if other than submission substance): 94.1334 g/mol
- Substance type: Organic
- Physical state: Solid
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source of test material: Cardinal Nutrition, Inc. (Vancouver, WA).
- Expiration date of the lot/batch: No data
- Purity: 99.9%

RADIOLABELLING INFORMATION (Not applicable)
- Radiochemical purity: N/A
- Specific activity: N/A
- Locations of the label: N/A
- Expiration date of radiochemical substance: N/A

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: stored at room temperature.
- Stability under test conditions: the formulations were stable for 32 days for concentrations ranging from 10 to 100 mg/ml when stored at room temperature.
- Solubility and stability of the test substance in the solvent/vehicle: No data
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No data

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: No data
- Preliminary purification step (if any): No data
- Final dilution of a dissolved solid, stock liquid or gel: No data
- Final preparation of a solid: No data

FORM AS APPLIED IN THE TEST (if different from that of starting material): No data

OTHER SPECIFICS: No data

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Taconic Farms, Germantown, NY
- Females (if applicable) nulliparous and non-pregnant: [yes]
- Age at study initiation: 7 to 9 weeks
- Weight at study initiation: between 145 and 215 g/rat
- Fasting period before study: No data available
- Housing: Quarantine in plastic cages
- Use of restrainers for preventing ingestion (if dermal): no
- Diet (e.g. ad libitum): Harlan Teklad Certified Rodent Diet #8728C, ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: Two weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 4 degC
- Humidity (%): No data available
- Air changes (per hr): No data available
- Photoperiod (hrs dark / hrs light): 12-h light/dark cycle

IN-LIFE DATES: From: To: No data available

Administration / exposure

Route of administration:
oral: gavage
Type of inhalation exposure (if applicable):
not specified
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Formulations were prepared in deionized water at 10, 100, and 200 mg/ml concentrations for the 50, 500, and 1000 mg/kg dose levels, respectively.

DIET PREPARATION
- Rate of preparation of diet (frequency): No data
- Mixing appropriate amounts with (Type of food): No data
- Storage temperature of food: No data

VEHICLE
- Justification for use and choice of vehicle (if other than water): No data
- Concentration in vehicle: 50, 500,1000 mg/kg
- Amount of vehicle (if gavage): 5 ml/kg
- Lot/batch no. (if required): No data
- Purity: No data
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Aliquots of the formulations were transferred to dosing vials and samples representing each dose level from the first preparation were analyzed by gas chromatography. The purity of MSM was 99.9%.
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1 mating scheme (i.e., one male:one female)
- Length of cohabitation: overnight
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy
- After ... days of unsuccessful pairing replacement of first male by another male with proven fertility. No data available
- Further matings after two unsuccessful attempts: no
- Verification of same strain and source of both sexes: no
- Any other deviations from standard protocol: To facilitate the teratogenic evaluation of pups, a staggered-start design (via staggered mating) was employed. Mating was staggered over six days resulting in six series.
Duration of treatment / exposure:
14 days (on gestation days 6–20)
Total exposure period: 20 days.
Frequency of treatment:
Daily
Duration of test:
Terminal killing: 21st day of gestation
Doses / concentrationsopen allclose all
Dose / conc.:
0 other: mg/kg
Remarks:
Vehicle group
Dose / conc.:
50 other: mg/kg
Dose / conc.:
500 other: mg/kg
Dose / conc.:
1 000 other: mg/kg
No. of animals per sex per dose:
Total: 98
0 mg/kg/day : 25 timed-bred primiparous dams
50 mg/kg/day : 24 timed-bred primiparous dams
500 mg/kg/day : 25 timed-bred primiparous dams
1000 mg/kg/day : 24 timed-bred primiparous dams

Control animals:
yes

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: No data
- Time schedule:
- Cage side observations checked in table [No.?] were included.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule:

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded on gestation days 0 (sperm-positive day/randomization), 3, 6, 9, 12, 15, 18, and 21.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Feed consumption was calculated for each period between weighings.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data
- Time schedule for examinations:

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: Gross necropsy consisted of examination of the brain and all organs in the thoracic and abdominal cavities of the dams.

Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
Fetal examinations:
- External examinations: Yes
- Soft tissue examinations: Yes
- Skeletal examinations: Yes
- Head examinations: Yes
Statistics:
Dam weights, litter body weights, and viability data were analyzed by a two-way analysis of variance (ANOVA). In the presence of a significan t main effect, all post-hoc comparisons were performed using Dunnett’s test (two-tail). Gross, visceral, cephalic, and skeletal data were analyzed by Chi-Square/Fisher’s Exact tests (fetal N) when incidence in the treated rats was higher (i.e., when the difference in the absolute number of fetuses affected is greater than three) than controls. A minimum statistical significance level of p ≤ 0.05 was used in all cases.
Indices:
No data
Historical control data:
No data

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
no effects observed
Description (incidence and severity):
No clinical signs of toxicity were observed.
Dermal irritation (if dermal study):
not examined
Mortality:
not specified
Body weight and weight changes:
no effects observed
Description (incidence and severity):
Body weight was similar among all groups.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
Feed consumption was not affected.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
Uterine weights were similar across all groups.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No gross external anomalies were observed.
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
No histopathological lesions in organ and tissues were observed.
Histopathological findings: neoplastic:
not specified
Other effects:
not specified
Details on results:
No evidence of maternal toxicity by test chemical was observed in this study.

Maternal developmental toxicity

Number of abortions:
not specified
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Changes in pregnancy duration:
not specified
Changes in number of pregnant:
not specified
Other effects:
not specified
Details on maternal toxic effects:
No evidence of maternal toxicity was observed. No effects observed on maternal body weight, uterus weight, body weight gain. No clinical signs of toxicity were observed.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
clinical signs
body weight and weight gain
food consumption and compound intake
organ weights and organ / body weight ratios
gross pathology
histopathology: non-neoplastic
pre and post implantation loss
total litter losses by resorption
early or late resorptions
dead fetuses
Remarks on result:
other: No evidence of maternal toxicity was observed.

Maternal abnormalities

Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Description (incidence and severity):
No significant differences in male, female or combined fetal weights were detected.
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
not specified
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
not specified
External malformations:
no effects observed
Description (incidence and severity):
No gross external anomalies were observed; all fetuses appeared normal and none were malformed.
Skeletal malformations:
no effects observed
Description (incidence and severity):
No treatment-related skeletal anomalies were seen in the low, mid or high dose groups.
Visceral malformations:
no effects observed
Description (incidence and severity):
No visceral malformations were observed in any of the fetuses examined.
Other effects:
no effects observed
Details on embryotoxic / teratogenic effects:
No evidence of embryo or fetal toxicity, or treatment related alterations in fetal body weights or fetal examinations (gross external, visceral, cephalic, or skeletal) was observed in this study upto 1000 mg/kg
No significant differences in litter viability, litter size, or litter body weight were detected.


Effect levels (fetuses)

Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
reduction in number of live offspring
fetal/pup body weight changes
changes in litter size and weights
external malformations
skeletal malformations
visceral malformations
Remarks on result:
other: No evidence of embryo or fetal toxicity was observed.

Fetal abnormalities

Abnormalities:
no effects observed

Overall developmental toxicity

Developmental effects observed:
not specified
Treatment related:
not specified

Applicant's summary and conclusion

Conclusions:
Under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity was considered to be 1000 mg/kg/day.
Executive summary:

The objective of the study was to determine the developmental toxicity potential of test chemical when administered orally to pregnant rats during the period of major organogenesis and histogenesis. In a preliminary dose-finding study, distilled microprill (i.e., microspherical pellets of test chemical) was administered by oral gavage at dose levels of 0 (vehicle control), 50, 250, 500, and 1000 mg/kg/day to 8–9 sperm-positive female Sprague–Dawley rats/group/day on gestation days 6–20. No evidence of maternal or fetal toxicity was observed. For the definitive developmental study, four groups of 24–25 timed bred primiparous female rats were administered 0, 50, 500, or 1000 mg/kg/day via gavage on gestation days 6–20. Maternal feed consumption, body weight, body weight gain, uterus weight and corrected body weight/body weight gain were unaffected by treatment. No evidence of maternal toxicity, and no significant differences in litter viability, litter size, or litter body weight were detected. Fetal evaluations failed to show any biologically significant increase in the incidence of anomalies in the treated groups, and no malformations were seen in any of the fetuses. No evidence of fetal mortality, alterations to growth, or structural alterations were observed in the fetuses of dams administered 50–1000 mg/kg/day. Therefore, under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity was considered to be 1000 mg/kg/day.