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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline Study and GLP

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1999
Report date:
1999

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Reference substance name:
2-ethylhexyl stearate
EC Number:
244-754-0
EC Name:
2-ethylhexyl stearate
Cas Number:
22047-49-0
IUPAC Name:
2-ethylhexyl stearate
Details on test material:
2-Ethylhexyl stearate is a colourless and odour-less liquid. It is insoluble in water and has a relative density of 0.86 g/cm3 and a mean molecular weight of 390 g/mol.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals or test system and environmental conditions:
Mated female Sprague-Dawley CD rats (specific pathogen free) were supplied (Charles River, Wiga GmbH, Sulzfeld, Germany) at day 0 of gestation (confirmed vaginal plug), and were randomly assigned (random tables) to test groups. Animals were acclimatized to laboratory conditions for 5 days. At the start of the study the primiparous animals were 8 wk old (mean body weight 197 g).
Animals were housed in a semi-barrier-sustained animal room with a controlled temperature of 21-23°C, 10 to 15 air changes/hr, relative humidity of 40-56% and a 12-hr light/dark cycle. Rats were caged individually in Makrolon type M3 cages. They were supplied with commercial pelleted diet (No. 1324, Altromin GmbH, Lage, Germany, analytically controlled per batch) and community tap water ad lib. (once weekly, controlled).

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: arachidis oil, DAB 10
Details on exposure:
Preparation of dosing solutions:
The dosing solutions were prepared daily before administration. Arachidis oil, DAB 10, was used as a vehicle for the test substance. The test solution was administered by gavage once daily, in the morning from day 6 up to day 15 post coitum (pc). All groups received a dose volume of 5 ml/kg body weight, adjusted to the body weight of day 6 pc. Control animals were similarly dosed with the vehicle alone.
Details on mating procedure:
see above
Duration of treatment / exposure:
see above
Frequency of treatment:
see above
Duration of test:
see above
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
100 mg/kg
Basis:
other: bodyweight
Remarks:
Doses / Concentrations:
300 mg/kg
Basis:
other: bodyweight
Remarks:
Doses / Concentrations:
1000 mg/kg
Basis:
other: bodyweight
No. of animals per sex per dose:
group size: 24 animals
Control animals:
yes, concurrent vehicle

Examinations

Maternal examinations:
Observations:
Clinical signs (day of gestation): 0-20, daily
Body weights (day of gestation): 0, 6, 16, 20
Body weight gains: calculated based on the body weight on day 0 of gestation

On day 20 pc, the females were sacrificed by ether overdose and the foetuses were removed by caesarean section. Post mortem examination included gross macroscopic examination of all maternal organs, with emphasis on the uterus, uterine contents, position of the foetuses and a record of the number of corpora lutea noted.
Ovaries and uterine content:
Post mortem examination included gross macroscopic examination of all maternal organs, with emphasis on the uterus, uterine contents, position of the foetuses and a record of the number of corpora lutea noted. The number and distribution of intrauterine implantations were recorded. The pre-implantation and post-implantation loss and intrauterine resorption sites were evaluated. Intrauterine deaths were classified on the basis of the absence (early resorption) and of the presence (late resorption) of foetal or decidual tissue in addition to placental tissue.
Fetal examinations:
Living and dead foetuses were removed from the uterus. The living foetuses were sexed, weighed individually with placentae and examined for gross external abnormalities.
Furthermore, foetal soft tissue and skeletal development were investigated. The Wilson technique was applied to half of the foetuses to evaluate potential visceral changes. The remaining foetuses were cleared in a solution of potassium hydroxide and stained with Alizarin Red. Alterations in foetuses were classified according to internal SOP into four categories: variations: slight and common structural changes occurring regularly in the control population; retardations: structural differences related to a delayed degree of skeletal ossification (transient stages of development); anomaly: slight relatively rare structural changes not obviously detrimental; malformations: severe rare and/or obviously lethal changes.
Statistics:
If the variables could be assumed to follow a normal distribution, the Dunnett test, based on a pooled variance, was applied for the comparison between the treated groups and the control group. The Steel 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 (Bonferroni-Holm corrected).

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:no effects

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Effect levels (fetuses)

open allclose all
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: embryotoxicity
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: fetotoxicity
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: teratogenicity

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

2-Ethylhexyl stearate did not effect maternal ratsduring the entire pregnancy. No mortalities occurred in the dams during the study, either in the vehicle control or in the groups exposed to 2-ethyl-hexyl stearate up to 1000 mg/kg body weight. The absolute and the corrected body weight and body weight gain was comparable between the groups. No deviation was observed during the treatment period. Gross macroscopic examination of the maternal organs including ovaries and uterus revealed no alterations.

 

Reproduction data:

The number of corpora lutea, implantation sites, living foetuses, foetal sex ratio, resorptions and foetal deaths, and foetal and placenta weight in treated groups were not significantly different tothose of the control group. No compound-related differences were noted between themean reproduction data.

There were no dose-related statistically significant differences in the conception rate, meannumber of corpora lutea or pre-implantation loss. With the exception of one dead foetus in the 1000 mg/kg body weight group all foetuses in treated and control groups were alive.

The weights of live foetuses exhibited no significant differences on a litter and individual basis. Incomparison with the control group in the 100 and 1000 mg/kg body weight group, the post-implantation loss and total embryonic deaths were significantly decreased. Non-dose-related findings were considered to be incidental, due to the high control values. Mean foetal placental and uterus weights were not affected by treatment. Foetal sex ratio wascomparable in all groups. A hydrops was noted in one control group foetus.

Incidences were also compared to the historical controls obtained in six developmental toxicity studies according to the OECD guideline No. 414 study design using the same strain (Sprague-Dawley CD). Findings both on the individual foetus and on the litter basis did not differ from thehistorical control.

From the visceral examinations, one hydrocephalus internus was found which has to be considered as an individual non-dose-related finding which also occurs in the historical data at a comparable level (0.4%). All changes were slight and also occurred in the control population.

Concerning the skeletal examination on the basis of the foetal incidence, there are differentiatedresults in some findings such as “non-ossification” of sternebrae (retardation). However, the total frequency of the findings `incomplete ossification including “non-ossification” of all sternebrae show no substantial differences between the untreatedand treated groups. The percentage of these findings varies from approximately 60% (dose group 0, 300 and 1000 mg/kg) up to 77% (dose group 100 mg/kg). There is also no difference to the historical control data showing a percentage of about 62%. The reason for the differentiated results may be the individual age-related development of the foetuses.

Therefore, it can be concluded that there were no differences in the incidences of external, visceral orskeletal malformations or variations among all groups.

Applicant's summary and conclusion

Conclusions:
Maternal data. The dams tolerated the applied dose levels of up to 1000 mg/kg without lethality. Maternal body weight gain was not affected by the treatment. For the maternal toxicity (MT) the following no-observed-adverse-effect level (NOAEL) can be deduced:
NOAEL(MT) = 1000 mg/kg body weight

Reproduction data. Apart from dose group 1000 mg/kg body weight (one dead foetus) all females had viable foetuses. Pre- and post-implantation loss and mean numbers of resorption were unaffected by treatment. All parameters were comparable with the animals of the control group. Skeletal and visceral investigations detected no treatment-related malformations. For the embryo/foetotoxicity and the teratogenicity (EFT/TER) the following NOAEL can be deduced:
NOAEL(EFT/TER) = 1000 mg/kg body weight
Executive summary:

This study is used as read across, because the ester bond of 2 -ethylhexyl stearate will be hydrolyzed by pH or enzymatic activities in the body. Thus, the C18 fatty acid stearate acid is released leading to an identical situation as in case of an exposure to C18 sodium salt where also the C18 fatty acid stearate is released as the relevant component.

In this study 2-Ethylhexyl stearate was investigated in an embryo-/foetotoxicity and teratogenicity study on rats according to OECD guidelines for the testing of chemicals (No. 414). Dose levels of 0 (arachidis oil), 100, 300 and 1000 mg/kg body weight/day were administered by gavage. Dams tolerated the applied dose levels without any toxic effects. Pre- and post-implantation loss and mean numbers of resorptions were unaffected by treatment. All parameters were comparable with the animals of the control group. Skeletal and visceral investigations revealed no treatment-related malformations. For embryo-/foetotoxicity, teratogenicity and maternal toxicity a NOAEL of 1000 mg/kg was deduced.