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Toxicological information

Toxicity to reproduction

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Administrative data

Endpoint:
two-generation reproductive toxicity
Remarks:
based on generations indicated in Effect levels (migrated information)
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study, published in peer-reviewed literature, minor restrictions in design and reporting, but otherwise adequate for assessment.

Data source

Reference
Reference Type:
publication
Title:
Results and evaluations of 48 continuous breeding reproduction studies conducted in mice
Author:
Morrissey RE, Lamb IV, JC, Morris RW, Chapin RE, Gulati DK, Heindel JJ
Year:
1989
Bibliographic source:
Fundamental and Applied Toxicology, 13, 747-777

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: NTP Reproductive Assessment by Continuous Breeding (RACB)
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): propylene glycol
- Molecular formula (if other than submission substance): C3H8O2
- Molecular weight (if other than submission substance): 76.0942
- Smiles notation (if other than submission substance): C([C@@H](C)O)O
- InChl (if other than submission substance): InChI=1/C3H8O2/c1-3(5)2-4/h3-5H,2H2,1H3
- Substance type: organic
- Physical state: liquid
- Analytical purity: not specified
- Impurities (identity and concentrations): not specified, but it is stated that all impurities which equaled 1.6% or more were identified.
- Stability under test conditions: stable in the dosing vehicle (water) for up to 14 days

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Kingston, NY.
- Age at study initiation: 6 weeks
- Housing: group housed by sex in solid-bottom polypropylene or polycarbonate cages with stainless-steel wire lids, during the quarantine and the 1-week premating periods. subsequently, the animals were housed as breeding pairs or individually
- Diet (e.g. ad libitum): ground rodent chow, ad libitum
- Water (e.g. ad libitum): deionized/filtered water

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ± 2
- Photoperiod (hrs dark / hrs light): 14/10

Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
Each concentration was mixed separately at periodic intervals.

VEHICLE
Water
- Concentration in vehicle: 1.00, 2.50 and 5.00%
Details on mating procedure:
In the continuous breeding study mice were exposed to the test substance for 7-day premating period, and were then randomly grouped as mating pairs and cohabited and treated continuously for 98 days. Data were collected on all newborns during this period within 12 hours of birth, after which each litter was discarded. After the 98-day cohabitation, the pairs were separated but continued on treatments. During the next 21 days, any final litters were delivered and kept for at least 21 days (weaning). The mother was dosed through weaning and F1 mice were dosed until mated at 74 ± 10 days of age. For this, male offspring were mated to female off-spring from the same treatment group (n = 20/group/sex) and the F2 litters were examined for litter size, sex and pup weight.
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
14 days in the dose range-finding study; 7 days pre-mating period, 98 days (14 weeks) cohabitation, 21 days post-cohabitation. Any litters delivered during these 21 days were kept for at least 21 days (weaning); dosing at 74 ± 10 days of age until mating (mother was dosed throughout).
Frequency of treatment:
Daily
Details on study schedule:
Other: A 14-day dose-setting study utilized one control group and 5 groups of dosed animals (8/sex/dose). The endpoints for this study were clinical signs, mortality, body weight gain and consumption of food and water.
In the main study, the litters were removed and examined as soon as possible after delivery was completed. The offsprings were sexed, weighed and killed so that the female may be impregnated immediately. This approach maximized the number of litters which could be produced in the 14-week breeding phase.
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0, 1.82, 4.80 and 10.10 g/kg bw/day (main study)
Basis:
actual ingested
Remarks:
Doses / Concentrations:
5% in water (post-cohabitation)
Basis:
nominal in water
No. of animals per sex per dose:
Dose range-finding study: 8/sex/dose
Main study: 20/sex/dose in each treatment group; 40/sex/dose in the control group
21 days post-cohabitation: 20/sex/dose (only the highest dose (5% in water) was tested).
Control animals:
yes
Details on study design:
- Dose selection rationale: based on a 14-day dose-selecting study
- Rationale for animal assignment: stratified randomization procedure based on body weights.

Other: when significant adverse effects on fertility were observed in the continuous breeding phase a crossover mating trial was usually performed to determine whether F0 males or females were more sensitive to the effects. High-dose animals of each sex were mated to control mice of the opposite sex to determine the affected sex. The high dose animals were selected to increase the possibility of detecting effects in the crossover mating. There were three combinations of control and treated mice: control males with control females, high-dose males with control females, and control males with high-dose females. The offspring of the crossover matings were analyzed as in Task 4, and the parents were necropsied. Results of mating high-dose mice with control group partners were compared to matings within the control group to determine which sex was adversely affected. The crossover mating was not done if significant reproductive effects were not observed in the continuous breeding phase.
Necropsies were performed in this series of studies, usually on only F0 mice involved in the crossover mating trial, when there was evidence of an effect on reproduction or, at the least, in the second generation even if there was no effects on the F0 mice. Endpoints examined for the females included selected organ weights and histology. At necropsy, the endpoints of male reproductive function included selected organ weights and histology, percentage motile sperm, epididymal sperm concentration, and percentage abnormal sperm. These multiple measured of fertility (whole animal, organ) were designed to increase the sensitivity of the RACB protocol.

Positive control:
Diethylstilbestrol and ethylene glycol monoethyl ether

Examinations

Parental animals: Observations and examinations:
Clinical signs, mortality, body weight gain and consumption of food and water were assessed during the 14-day dose-setting study.
Oestrous cyclicity (parental animals):
Not performed.
Sperm parameters (parental animals):
As no adverse effects on fertility were observed in the continious breeding study, the subsequent substudy (crossover mating with subsequent examination of male reproductive function in F0 animals) was not performed.
Litter observations:
PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
mean No. litters per pair, mean No. live pups per pair, mean No. live male pups per litter, mean No. live female pups per litter, proportion of pups born alive, sex of pups born alive, mean live pup weight per litter, mean live male pup weight per litter, mean live female pup weight per litter; adjusted mean live pup weight per litter; adjusted mean live male pup weight per litter; adjusted mean live female pup weight per litter, body weight.



Postmortem examinations (parental animals):
As no adverse effects on fertility were observed during the continious breeding study, subsequent crossover mating with subsequent necropsies of F0 animals was not performed.
Postmortem examinations (offspring):
Not performed.
Statistics:
Dose-related trend in fertility: the Cochran-Armitage test (Armitage, 1971)
Pairwise comparisons involving mating and fertility indices: Fisher's exact test
Overall differences in number of litters, number of live pups, proportion of life pups and the sex ratio for dose group means: Kruskal-Wallis test (Conover 1980)
Ordered differences in number of litters, number of live pups, proportion of life pups and the sex ratio for dose group means: Jonckheere's test (Jonckheere, 1954)
Pairwise comparisons of treatment group means: Wilcoxon-Mann-Whitney U test
Average pup weight: Kruskal-Wallis test
Treatment differences in average pup weight: analysis of covariance (Neter and Wasserman, 1974)
Pairwise comparisons: two-sided t test
Organ weights: analysis of covariance F test (overall equality) and t test (pairwise equality)
Reproductive indices:
Fertility index was determined as (No. fertile/No.cohabited) x 100
Mating index was determined as No. females with plugs/No. cohabited
Offspring viability indices:
No data.

Results and discussion

Results: P0 (first parental animals)

General toxicity (P0)

Clinical signs:
not specified
Body weight and weight changes:
not specified
Food consumption and compound intake (if feeding study):
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
not specified
Other effects:
not specified

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:
not specified
Reproductive function: sperm measures:
not specified
Reproductive performance:
no effects observed

Details on results (P0)

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS): no effects on fertility index was observed in P animals.

Effect levels (P0)

Dose descriptor:
NOAEL
Remarks:
toxicity
Effect level:
10 100 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: No effects reported at the highest dose tested.

Results: F1 generation

General toxicity (F1)

Clinical signs:
not specified
Mortality / viability:
not specified
Body weight and weight changes:
no effects observed
Sexual maturation:
not specified
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Histopathological findings:
not examined

Details on results (F1)

No effects on fertility index or mating index in F1 animals was observed.

No differences were found between control and test P animals in the mean No. litters per pair, mean No. live pups per pair, mean No. live male pups per litter, mean No. live female pups per litter; proportion of pups born alive; sex of pups born alive; mean live pup weight per litter; mean live male pup weight per litter; mean live female pup weight per litter; adjusted mean live pup weight per litter; adjusted mean live male pup weight per litter; adjusted mean live female pup weight per litter.

No differences were found between control and F1 animas in mean No. live pups per litter; mean No. liver male pups per litter; mean No. live female pups per litter; proportion of pups born alive and sex of pups born alive.

Effect levels (F1)

Dose descriptor:
NOAEL
Remarks:
fertility
Generation:
F1
Effect level:
10 100 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: No effects on fertility of F1 generation were observed at the highest dose.

Results: F2 generation

Effect levels (F2)

Dose descriptor:
NOAEL
Remarks:
developmental effects
Generation:
F2
Effect level:
10 100 mg/kg bw/day
Sex:
male/female
Basis for effect level:
other: No effects on litter size, sex and pup weight in F2 pups were observed at the highest dose.

Overall reproductive toxicity

Reproductive effects observed:
not specified

Applicant's summary and conclusion