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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1978
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study, not conducted according to GLP.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1978
Report Date:
1978

Materials and methods

Principles of method if other than guideline:
TDCP was administered daily to 20 mated Sprague Dawley female rats/dose group by oral gavage from days 6-15 of gestation
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): FR-2 (Fyrol)
- Physical state: clear, viscous liquid
- Dosage calculations were based upon an assumed purity of 100%

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River breeding Laboratories Inc, Wilmington, MA.
- Age at study initiation: no data
- Weight at study initiation: no data
- Fasting period before study: no data
- Housing: Housed individually in a hanging wire cage with access to food and water
- Diet: ad libitum (Purina Laboratory Chow)
- Water: ad libitum
- Acclimation period: 27 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Photoperiod (hrs dark / hrs light): no data

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Appropriate amount sof test material were mixed on a weight-per-volume basis in a vehicle of corn oil at concentrations of 12.5, 50 and 200 mg/ml


DIET PREPARATION
- Rate of preparation of diet (frequency): weekly
- Mixing appropriate amounts with (Type of food): corn oil
- Storage temperature of food: approx. 4 degrees centigrade
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Data are not available, however from the study report it was indicated that samples of each test solution (one sample taken at the time of preparation and one sample taken at the end of each dosing week - for a total of three weeks) were frozen and sent to the sponsor for analysis of the concentrations of the test material. Samples of corn oil vehicle were also sent to the sponsor.
Details on mating procedure:
Subjects are mated prior to study acceptance.
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/2
- Length of cohabitation: until mated
- Proof of pregnancy: sperm in vaginal smear, referred to as day 0 of pregnancy
Duration of treatment / exposure:
Subjects were treated from days 6 - 15 of gestation.
Frequency of treatment:
Daily
Duration of test:
10 days.
No. of animals per sex per dose:
20 Females per dose group and 20 females in control group.
Control animals:
yes, concurrent vehicle

Examinations

Maternal examinations:
Mortalities, clinical signs, body weight, feed consumption and necropsy were carried out on adult females.
Ovaries and uterine content:
Numbers of corpora lutea, implantations, resorptions, live foetuses and dead foetuses were noted.
Fetal examinations:
One third of the foetuses were examined by serial whole body sectioning using Wilson’s technique. The remaining foetuses were eviscerated, fixed and examined for skeletal abnormalities using alizarin red staining.
Statistics:
The mean gains in maternal body weights, mean maternal food consumption values, mean ovarian, uterine and litter data and the mean fetal weights and lengths of each treated group were compared to the control group by Student's T-test when the variances of the two groups were not found to differ statistically (F significant), Cochran's approximation of t(t') was utilised. The reproduction indices of the control and treated groups were analysed by the chi-square method. All statistcial analyses were evaluated at a probability level of 0.05.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
There were three mortalities at the highest dose. These may have been caused by intubation errors, as findings at necropsy were not considered indicative of treatment-related effects. Clinical signs of toxicity were marked in most animals of the high dose and consisted of urine stains (19/20), hunched appearance (20/20), salivation (18/20) and alopecia (7/20). Rough coat (3/20), bloody crust around the nose (3/20), thinness (2/20) and depression (1/20) were noted in number of high dose animals also. Some clinical signs were also noted in the mid dose group and these may have been treatment-related (alopecia (1/20), hunched appearance (3/20), rough hair coat (1/20) and urine stains (5/20)). There was a significant body weight loss in mid and high dose animals from days 6-11 of treatment. These treated animals lost 15.6 g and 28.9 g, respectively, when compared to untreated animals who gained 22.1 g during this period. From days 11-15, mean weight gain of mid and low dose groups was not different from control, while mean weight gains were reduced in the 400 mg/kg/day group (50% of control). The overall mean weight gain from days 0-19 was significantly reduced (p<0.05) at 400 mg/kg/day (56% of controls). The mean weight gain in low and mid dose animals was not different to that of untreated animals. Mean food consumption was significantly reduced to 84.8% at 100 mg/kg/day (days 7-11) and at 400 mg/kg/day to an average of 45% throughout treatment. There were no specific findings at necropsy, which were indicative of a treatment-related effect.

Pregnancy rates were unaffected by treatment. The mean number of corpora lutea and implantation sites and the implantation efficiencies of the treated animals surviving to day 19 of gestation were similar to or exceeded control values.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
25 mg/kg bw/day
Basis for effect level:
other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
The authors considered that data for mean weight and crown-rump length from two of the 100 mg/kg/day litters should be removed, as they appeared to be of an older gestation age. When this was done, there was a slightly lower mean foetal weight (2.21 g) and crown-rump length (3.18 cm) for the 400 mg/kg/day litters when compared to controls (2.42 g and 3.35 cm) respectively, although these did not reach statistical significance. The finding of increased incidence of dilated lateral ventricles of the brain was slight and within the historical control range. There was considerable evidence of retarded skeletal development in the high dose group; incomplete ossification of intraparietal and supraoccipital, nonossified hyoid and nonossified centres in the sternebrae, nonossified centre of the sacral and caudal portions of the vertebrae, nonossified arches of the sacral vertebrae and incomplete ossification of the pubis, and nonossified centres in the metacarpels and metatarsels. Such findings are consistent with the reduced foetal weight, length and viability at this dose level and indicate developmental retardation which may be related to the maternal toxicity seen at 400 mg/kg/day. The finding of increased incidence of foetuses with angulated ribs at 400 mg/kg/day may have been related to treatment but is of unknown biological significance (no historical control data for this effect was included in the report).

Results indicated embryotoxicity in the high dose group. In this group, the rate of resorptions was statistically significantly increased when compared to controls (14.4 % compared to 6.7 %). The foetal viability index for the high dose group was statistically significantly lower than control. No increase was seen at the low or mid doses.

Effect levels (fetuses)

Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day (nominal)
Basis for effect level:
other: This is based on the statistically significant increased resorptions and the decreased foetal viability index at 400 mg/kg/day.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Under the conditions of this study Fyrol FR-2 produced no apparent compound-related effects when administered at a dose level of 25 mg/kg bw. Maternal toxicity, limited to adverse effects on body weight and food consumption, was evident at a dose level of 100 mg/kg bw. At the high test level of 400 mg/kg bw, signs of maternal toxicity included adverse clinical findings and dose-related effects on body weight and food consumption. In addition, there were signs of embryo- and fetotoxicity at the high test level which were not expected due to the maternal toxicity observed.