1,2-bis(2-methoxyethoxy)ethane

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 1984 - May 1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

food consumption not reported

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,2-bis(2-methoxyethoxy)ethane

EC Number:

203-977-3

EC Name:

1,2-bis(2-methoxyethoxy)ethane

Cas Number:

112-49-2

Molecular formula:

C8H18O4

IUPAC Name:

2,5,8,11-tetraoxadodecane

Constituent 2

Reference substance name:

Triglyme

IUPAC Name:

Triglyme

Constituent 3

Reference substance name:

Triethylene glycol dimethyl ether

IUPAC Name:

Triethylene glycol dimethyl ether

Details on test material:

Source: Aldrich Chemical Co.
Lot: L50826KJ
Purity: 98.5%

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hazelton-Dutchland Laboratory Animals, Inc. (Denver, PA, USA)
- Age at study initiation: approx. 6 months
- Weight at study initiation: 2.4 - 4.6 kg
- Housing: singly in stainless steel cages with mesh flooring
- Diet (e.g. ad libitum): Purina Certified Chow 5322, ad libitum
- Water (e.g. ad libitum): deionized/flitered water, ad libitum
- Acclimation period: 14 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23.3 +/- 2 °C (preliminary study I), 23.9 +/- 1 °C (preliminary study II), 23.3 +/- ´1 °C (main study)
- Humidity (%): 56+/- 7% (preliminary study I), 46 +/- 6% (preliminary study II), 33 +/- 12% (main study)
- Air changes (per hr): 12 - 14
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

A) In preliminary study I Triglyme was administered to inseminated rabbits on gestation day (gd) 6-19 at doses of 0, 500, 1000, 1500, and 2000 mg/kg bw/d.
B) In preliminary study II Triglyme was given at doses of 0, 10, 50, 100, 200, 300, and 400 mg/kg bw/d on gd 6-19.
C) Doses for the main study included 0, 75, 125, 175, and 250 mg/kg bw/d.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Gas chromatography

Details on mating procedure:

atrificially inseminated

Duration of treatment / exposure:

gd 6 through 19 (14 days)

Frequency of treatment:

daily

Duration of test:

duration of treatment: 14 days
termination: gd 30

No. of animals per sex per dose:

Preliminary studies I and II: 6
Main study: 25 (sum of three replicate studies)

Control animals:

yes, concurrent vehicle

Details on study design:

- Preliminary studies I and II
Timed-inseminated females were weighed on gd 0, 6-19, and 30 and were observed daily during treatment for clinical signs of toxicity. On gd 30, inseminated doses were sacrificed by an iv injection of T-61 Euthanasia Solution, and evaluated for gross signs of toxicity. Body weight, liver weight, gravid uterine weight, and status of uterine contents were recorded. Liver fetuses were dissected from the uterus and sacrificed by an intracardiac injection of t-61 Euthanasia Solution. Individual fetuses were weighed and examined for external morphological abnormalities. Following examination, al maternal and fetal carcasses and organs were discarded.

- Main study
Each inseminated doe was weighed on gd 0, gd 6 through 19, and gd 30, and was also observed daily during treatment for clinical signs of toxicity. On gd 30, inseminated does were sacrificed by an iv injection of T-61 Euthanasia Solution and evaluated for gross signs of toxicity. Body weight, liver weight, gravid uterine weight, and status of uterine contents were recorded. Live fetuses were dissected from the uterus and sacrificed with approx. 0.25 mL ip T-61 Euthanasia Solution. Individual live fetuses were weighed and examined for external morphological abnormalities. All live fetuses were sexed and examined for visceral malformations using a fresh tissue dissection method. Half of the live fetuses were decapitated after dissection and the heads were fixed in Bouin's solution for free hand sectioning and examination. All fetal carcasses were prepared with Alcian Blue/Alizarin Red S stain and examined for skeletal malformations. Malformations were documented with photographs and/or sketches if an abnormality was unususal and/or a written description alone was inadequate. Maternal and fetal organs, as well as maternal carcasses were discarded. Fetal carcasses were stored in Glycerin:70% Ethanol (1:1) following examination of skeletal structures; decapitated (50%) fetal heads were stored in 70% Ethanol solution.

Examinations

Maternal examinations:

Body weight: gd 0, 6-19, and 30
Clincal signs/mortality: daily
At termination: gross pathology, Body weight, liver weight

Ovaries and uterine content:

status of uterine contents

Fetal examinations:

All live fetuses were sexed and examined for visceral malformations using a fresh tissue dissection method. Half of the live fetuses were decapitated after dissection and the heads were fixed in Bouin's solution for free hand sectioning and examination. All fetal carcasses were prepared with Alcian Blue/Alizarin Red S stain and examined for skeletal malformations.

Statistics:

Nonparametric statistics were used for data from both preliminary studies. Where appropriate, the litter was used as the unit of measurement. For data expressed as mean +/- S.E..M, Jockheere's Test for k independent samples was used to identify significant dose-response trend. Kruskal-Wallis one-way analysis of variance by ranks was used to test for overall differences among dose groups. When a Kruskal-Wallis test was significant (p<0.05), the Mann-Whitney U Test was used to make individual comparisons between the vehicle control and the Triglyme-treated groups. A one-tailed Mann-Whitney U Test was used for all parameters except measures of maternal and fetal body weight, and maternal organ weight for which a two-tailed test was used. For data for which expression of mean +/- S.E.M. values were not suitable, nominal scale data were reported, and analysed using a Test for Linear Trend on Proportions to identify dose-response trends, a Chi-Square Test for Independence to detect differences among treatment groups, and for parameters for which Chi-Square Test was significant a one-tailed Fisher Exact probability Test to detect differences between the vehicle control and each Triglyme-treated group.
Main study: please refer to "Any other information"

Indices:

no data

Historical control data:

Historical control data involving 1142 pregnant control NZW rabbits have been summarised by the Middle Atlantic Reproduction and Teratology Society.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes. Remark: clinical signs

Details on maternal toxic effects:
- Preliminary study I
Clinical signs in pregnant does were observed in all treated groups and included ataxia, lethargy, dyspnea and wheezing. There was 100% mortality in all but one treatment groups. The mortality for pregnant rabbits was 20% (0 mg/kg bw/d), 75% (500 mg/kg bw/d), 100% (1000 mg/kg bw/d), 100% (1500 mg/kg bw/d), and 100% (2000 mg/kg bw/d). There were no pregnant animals available for evaluation at scheduled sacrifice in the 1000, 1500, or 2000 mg7kg bw/d dose groups.

- Preliminary study II
Clinical signs of toxicity were noted primarily at doses of 50 mg/kg bw/d and above and included weight loss, lacrimation, bleeding, and absence of feces. The mortality was 0% (0 mg/kg bw/d), 0% (10 mg/kg bw/d), 0% (50 mg/kg bw/d)), 0% (100 mg/kg bw/d), 0% (200 mg/kg bw/d), 0% (300 mg/kg bw/d) and 33.3% (400 mg/kg bw/d). Maternal weight did not differ among treatment groups on gd 0, or prior to initiation of dosing on gd 6. On gd 12, 19, and 30, maternal body weight exhibited a significant downward trend that was not strictly dose-related, but appeared to be determined primarily by the 300 and 400 mg/kg bw/d groups. Maternal weight gain during gestation (gd 1-30) and treatment (gd 6-19) exhibited a similar decrease, with the high dose group being the most affected. Corrected maternal weight gain and absolute maternal liver weight were unaffected by Triglyme treatment.

- Main study:
Minor signs of toxicity included lacrimation, alopecia, weight loss, and absence of feces. During the study two animals in the 75 mg/kg bw/d group died from causes that could not be directly attributed to experimentor error. Specifically, one dam died on gd 18 while aborting her litter. the other dam was found dead on gd 18 without exhibiting distictive clinical signs and upon necropsy exhibited an intact esophagus but hemmorhagic lungs. Thus, the mortality for rabbits exposed to Triglyme was 0%, 8.3%, 0%, 0%, and 0% for the control through high dose groups, respectively. Maternal body weight did not differ significantly among tretment groups on gd 0, gd 6, or on gd 12. On gd 19, maternal body weight exhibited a significant decreasing trend with the 175 mg/kg bw/d group representing the NOEL. Maternal weight gain during the treatment period exhibited a decreasing trend with the 175 mg/kg bw/d group and above significantly below controls. Corrected maternal weight gain was not significantly affected by treatmetn, but gravid uterine weight exhibited a dose-related decreasing trend. Absolute maternal liver weight increased in a dose-related manner with 75 mg/kg bw/d representing a NOEL.

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

125 mg/kg bw/day (actual dose received)

Basis for effect level:

body weight and weight gain

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes. Remark: embryotoxicity, malformations

Details on embryotoxic / teratogenic effects:
- Preliminary study I
The one pregnant doe available for evaluation in the 500 mg/kg bw/d dose group on gd 30 had 100% resorptions.

- Preliminary study II
Of the animals in the 200, 300 and 400 mg/kg bw/d dose groups, 1 doe in the 200 mg/kg bw/d group, 5 does in the 300 mg/kg bw/d group, and 4 does in the 400 mg/kg bw/d dose group had only imlantation sites, and no live fetuses. All other pregnant animals produced live llitters.
Gravid uterine weight exhibited a decreasing trend with the 10, 50, 100, and 200 mg/kg bw/d groups representing no effect levels and the 300 and 400 mg/kg bw/d dose groups significantly below controls. Pregnant does did not differ signifiacntly among treatment groups in the number of implatation sites per litter, indicating that the does were similar with respect to reproductive status prior to exposure to Triglyme. The percent resorptions per litter, percent nonlive implants (resorptions plus dead fetuses) per litter, and percent adversely affected implants (nonlive implants plus malformed live fetuses) per litter exhibited a dose-related increase that was determined by 200, 300, and 400 mg/kg bw/d groups, with the 100 mg/kg bw/d group respresenting the NOEL and the 300 and 400 mg/kg bw/d groups significantly above controls. The percent dead fetuses per litter was unaffected by treatment. Triglyme had no effect on the number of litters with resorptions, dead fetuses, nonlive implants, or adversely affected imlants. For litters with live fetuses (0, 10, 50, 100, 200, and 300 mg/kg bw/d), average fetal body weight per litter was not affected by treatment. Triglyme did not cause a significant increasing trend in the percent externally malformed fetuses per litter, with the 100 mg/kg bw/d representing a NOEL, and the 200 mg/kg bw/d group significantly increased compared to the control group. The incidence of fetuses with one or more external malformation per litter was 0% for 0, 10, 50 and 100 mg/kg bw/d, and 38.5% and 75% for the 200 and 300 mg/kg bw/d groups, respectively. In the 200 mg/kg bw/d dose group, 3 of the 6 malformed fetuses had syndactyly and cleft palate, one fetus had foreshortened nasals and no external nares, and two fetuses had cleft palate. In the 200 mg/kg bw/d group in the one litter with live fetuses, gastroschisis, cleft palate, and umbilical hernia were noted as single malformations.

- Main study
Of the pregnant does surviving the scheduled sacrifice, the number of the does with entirely resorbed litters and no live fetuses was 1, 1, 2, 2, and 7 for the 0, 75, 125, 175, and 250 mg/kg bw/d groups, respectively. There was no significant difference among the treated groups in the number of corpora lutea per doe, or the number of implantation sites per litter.The percent preimplantation loss, however, exhibited a significant increasing trend that apeared to be determined by the high dose group. The percent resorptions per litter, the percent non-live implants, and percents adversely affected implants each increased in a dose-dependent manner. For the percent resorptions per litter the 75 mg/kg bw/d group was a NOEL. The percent non-live implants per litter was significantly increased over controls in the 250 mg/kg bw/d group. For the % adversely affected implants/litter, both the 175 and 250 mg/kg bw/d groups were significantly elevated above controls. The % dead fetuses/litter and % litters with resoprtions or with dead fetuses were not significantly affected by Triglyme treatment. The % of litters with non-live implants exhibited a significant treatment effect that was determined by the 175 and 250 mg/kg bw/d groups. The % of liiters with adversely affected implants exhibited an increasing trend with both the 175 and 250 mg/kg bw/d dose groups significantly above controls. for litters with live fetuses, the number of live fetuses/litter exhibited a significant decreasing trend that was determined by the 125, 175, and 250 mg/kg bw/d dose groups, with 75 mg/kg bw/d representing the NOEL. Triglyme had not significant effect on the sex ratio of live litters, average fetal body weight/litter, or average male or female fetal body weight/litter. Triglyme treatmetn caused a significant increasing trend in the % fetuses having one or more malformations/litter, with the 175 and 250 mg/kg bw/d dose groups significantly increased over controls. The % litters with one or more malformed fetuses exhibited a significant dose effect with the 175 and 250 mg/kg bw/d groups significantly above controls, but the increase in this parameter was not strictly dose-related at lower doses. For both external and visceral malformations, the 125 mg/kg bw/d was the NOEL. Malformations observed most frequently included missing toenails in fetuses of normal size with no digital abnormalities, abnormally small spleen, and hydronephrosis. Variations that were noted as unusual were an abnormal number of papillary muscles, clubbed limbs without bone change, and small cysts on the reproductive organs of both sexes.

Effect levels (fetuses)

Key result

Dose descriptor:

NOEL

Effect level:

75 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reduction in number of live offspring

skeletal malformations

visceral malformations

Overall developmental toxicity

Key result

Developmental effects observed:

yes

Lowest effective dose / conc.:

125 mg/kg bw/day

Treatment related:

yes

Relation to maternal toxicity:

developmental effects in the absence of maternal toxicity effects

Dose response relationship:

yes

Relevant for humans:

presumably yes

Applicant's summary and conclusion

Conclusions:

Exposure of New Zealand white rabbits to Triethylene glycol dimethyl ether at 75 mg/kg bw/d during gd 6 through 19 produced no adverse developmental effects. Doses of 125 mg/kg bw/d and above were associated with embryo toxicity. The NOEL (maternal) is considered to be 125 mg/kg bw/d.

Executive summary:

Triethylene glycol dimethyl ether was administered by gavage on gd 6 through 19 at doses 0, 75, 125, 175, or 250 mg/kg bw/d to pregnant Nwe Zealand White rabbits. During treatment, does exhibited clinical signs of toxicity consisting primarily of lacrimation, alopecia, weight loss, and absence of feces. Exposure to Triglyme did not increase maternal mortality. Maternal body weight and gravid uterine weight were significantly reduced at 250 mg/kg bw/d, wheras maternal weight gain during treatment wqs significantly depressed at doses of 175 mg/kg bw/d and above. Relative maternal liver weight was elevated at 250 mg/kg bw/d. Prenatal mortality was significantly increased compared to the control group at 250 mg/kg bw/d and was primarily due to an increased incidence of resorption of implanted embryos.The % adversely affected implants/litter and % litters with adversely affected implants was significantly increased compared to the control group at both the 175 and 250 mg/kg bw/d dose levels. Live litter size tended to be reduced but not was not significantly different from controls at any dose level of Triethylene glycol dimethyl ether. Average fetal body weight was unaffected by treatment. Triglyme at doses of 175 and 250 mg/kg bw/d caused a significant increase in the incidence of malformed fetuses per litter, and in the incidence of litters with malformed fetuses. A significant increase in the number of litters with one or more fetuses with external (gross) and visceral malformations was detected at 175 and 250 mg/kg bw/d. Malformations noted most frequently in fetuses of normal size included missing toenails with no digital abnormalities, abnormally small spleen and hydronephrosis. Variations of development that were noteworthy included an abnormal number of papillary muscles, clubbed limbs without skeletal change, and cysts on the reproductive organs of both sexes.

A NOEL (maternal) was derived at 125 mg/kg bw/d based on body weight and weight gain, and minimal evidence of maternal toxicity at 175 mg/kg bw/d as evidenced by relatively small decreases in maternal body weight and weight gain that apeared to be secondary to embryofetal toxicity.

A NOEL (developmental) was set at 75 mg/kg bw/d, an indication of an increase in embryo toxicity at 125 mg/kg bw/d and above, and significant embryo toxicityat 250 mg/kg bw/d, as reflected in % resoprtions/litter.