2,2'-ethylenedioxydiethyl bis(2-ethylhexanoate)

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well documented GLP study according to international guideline.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,2'-ethylenedioxydiethyl bis(2-ethylhexanoate)

EC Number:

202-319-2

EC Name:

2,2'-ethylenedioxydiethyl bis(2-ethylhexanoate)

Cas Number:

94-28-0

Molecular formula:

C22H42O6

IUPAC Name:

2-(2-{2-[(2-ethylhexanoyl)oxy]ethoxy}ethoxy)ethyl 2-ethylhexanoate

Details on test material:

- Name of test material (as cited in study report): 2,2’ -ethylenedioxydiethyl bis(2-ethylhexanoate), 3G8
- Appearance: colourless liquid
- Analytical purity: >97%
- Impurities (identity and concentrations):
- Composition of test material, percentage of components:
- Lot/batch No.: 2X010
- Expiration date of the lot/batch: 2013-04-16
- Manufacturer: Solutia UK Limited, Corporation Road Newport, South Wales, Gwent NP19 4XF, United Kingdom
- Storage condition of test material: refrigerator (2-8°C)

Test animals

Species:

rat

Strain:

other: Crl:WI

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, D-97633, from SPF colony
- Age at study initiation: young adult rats, approx. 7 weeks at the onset of treatment
- Weight at study initiation: main study: males: 251-287g, females: 157-198g; satellite: males: 246-295g, females: 162-211g
- Housing: Type III polycarbonate
- Diet: ad libitum, ssniff® SM R/M "Autoclavable complete feed for rats and mice – breeding and maintenance" (ssniff Spezialdiäten GmbH, D-59494 Soest)
- Water: ad libitum, tap water from municipal supply, as for human consumption
- Acclimation period: ≥ 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.0-23.4°C
- Humidity (%): 35-68 %
- Air changes (per hr): 15-20
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: propylene glycol containing 1% polysorbate 80

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
The required quantity of the test item was weighed with accuracy of 10 mg into calibrated mixing vessels. The required amount of polysorbate (Tween 80) was added to achieve 1% polysorbate content in dose solutions (e.g. 100 µl polysorbate was added, if final volume was 10 mL). Dosing solution was made by adding the required amount of propylene glycol to achieve the final volume and desired concentrations (192, 48 and 16 mg/mL) of the test item for each dose level (480, 120 and 40 mg/kg bw/day, respectively) and was stirred until a homogenous dosing form was obtained.

VEHICLE
- Justification for use and choice of vehicle: test item was stable in propylene glycol containing 1% Polysorbate 80 in the concentration range of 10 mg/mL- 250 mg/mL for 5.5 hours at room temperature and for up to three days when stored refrigerated at 2-8ºC
- Concentration in vehicle: 16, 48 and 192 mg/mL
- Amount of vehicle (if gavage): 2.5 mL/kg bw/day
- Lot/batch no. (if required): propylene glycol: SZBC0820V (99.7%) and SZBC2900V (≥ 99.5%), polysorbate 80: BCBH5882V and BCBJ7603V

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analysis of test item formulations for concentration and homogeneity was performed using a validated GC method, in the Analytical Laboratory of CiToxLAB Hungary Ltd. Duplicate top, middle and bottom samples were taken from test item formulations on four occasion (during the first, second, eighth and the last weeks of treatment). Similarly, one sample was taken in duplicate from the Group 1 (control) solution for concentration measurements.

Duration of treatment / exposure:

90 days

Frequency of treatment:

daily

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 40, 120, 480 mg/kg bw
Basis:
actual ingested

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

other: positive control treated with cyclophosphamide

Details on study design:

- Dose selection rationale: The dose levels were selected by the Sponsor in consultation with the Study Director, based on the available data, including the results of a dose range finding study performed by the Sponsor with the test item at CiToxLAB Hungary Ltd., where doses of 300, 600 and 1000 mg/kg bw/day were administered to Wistar rats for 14 consecutive days. In this study the treatment was well tolerated and no signs of overt toxicity were observed, however haematological changes (increased % of lymphocytes versus decreased % of neutrophils in males) and serum biochemistry changes (increased calcium, phosphate, potassium in females) and slightly higher thyroids weights were found in both sexes at 1000 mg/kg bw/day.
According to the Sponsor’s information, results from a combined 28-day repeated dose toxicity study with the reproduction/developmental toxicity screening test of 2,2’-ethylenedioxydiethyl bis (2-ethylhexanoate) in rats, performed according to OECD 422 by dietary administration, are available. In this study a parental NOAEL was found to be of 5000 ppm test item concentration in rodent diet (Mid dose level), equivalent to 314-576 mg/kg bw/day test item intake. Target organs at 15000 ppm (equivalent to 977-1563 mg/kg bw/day) were adrenal glands, kidneys, liver, pituitary gland, spleen, thymus and thyroid glands.
For this 90-day repeated dose toxicity study in rats, dose levels of 40 – 120 – 480 mg/kg bw/day were selected. The high dose is based on the findings at the highest dose in the 14-day DRF study (CiToxLab P12/072-101PE, 2012) and the NOAEL of 314-576 mg/kg bw/day in the OECD 422 study (NOTOX Project 491295, 2010).
- Rationale for animal assignment: During the acclimation period, the animals were assigned to their respective dose groups by stratified allocation based on body weights. Animals were randomly allocated to the control and dose groups based on the most recent actual body weight. SPSS/PC+ software was used in order to verify homogeneity/variation among/within groups. Males and females were randomized separately.

Positive control:

An additional group of age matched positive control animals for TDAR was treated with cyclophosphamide via intraperitoneal injection for six consecutive days. (Cyclophosphamide monohydrate, a known immunosuppressant, was administered at 25 mg/kg body weight/day).

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Morbidity and mortality twice daily. General clinical observations were made at least once a day at approximately the same time.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Detailed clinical observations outside the home cages were made on all animals at randomisation (Day -1 or -2) and once a week thereafter, before treatment.
- Observations were performed on the skin, fur, eyes, eyeballs and mucous membranes, autonomic activity (lachrymation, piloerection, pupil size, respiratory pattern, occurrence of secretions and excretions), circulatory and central nervous system (tremor, convulsion, muscular contractions, etc.), somatomotor activity and behaviour pattern (changes in exploratory behaviour, ordinary behaviour including changes in grooming, headshaking, gyration, etc., abnormal behaviour such as autophagia/self-mutilation, backward motion, abnormal vocalization, aggression, etc.), motor coordination, ambulatory abnormalities, changes in body position and posture (hunchback posture, etc), gait, posture and response to handling and to environmental stimulation. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhoea, lethargy, sleep and coma.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded with a precision of 1 g at randomisation, on Day 0, prior to start of treatment, then weekly, including on Day 89 (last treatment day) and Day 117 (last day of recovery), and prior to necropsy (fasted, on Days 90 or 118).

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Ophthalmoscopy examination was conducted in all animals before initiation of the treatment and in the Control Group 1 and High dose Group 4 animals, during Week 13. No treatment related alterations are found at Week 13 (Day 85), therefore no examination of the lower dose groups and recovery groups was necessary.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of the treatment or recovery periods, prior to scheduled necropsy on Day 90 or 118
- Animals fasted: Yes
- How many animals: all animals
- Parameters checked: red blood cell count, haemoglobin concentration, haematocrit (%), mean corpuscular (erythrocyte) volume, mean corpuscular (erythrocyte) haemoglobin, red cell (erythrycyte) distribution width (%), platelet (thrombocyte) count, mean platelet (thrombocyte) volume, reticulocyte count (absolute and %), white blood cell (leukocyte) count, neutrophil (absolute and %), lymphocyte (absolute and %), monocyte (absolute and %), eosinophil (absolute and %), basophil (absolute and %), large unstained cells (absolute and %)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of the treatment or recovery periods, prior to scheduled necropsy on Day 90 or 118
- Animals fasted: Yes
- How many animals: all surviving animals
- Parameters checked: glucose, total bilirubin concentration, urea concentration, cholesterol concentration, triglycerides, creatinine concentration, phosphorus concentration, sodium concentration, potassium concentration, calcium concentration, chloride concentration, total protein concentration, albumin concentration, Alb/glob ratio, aspartate aminotransferase activity, alanine aminotransferase activity, alkaline phosphatase, gamma glutamyltransferase activity, bile acids

URINALYSIS: Yes
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked: leukocyte, nitrite, pH, protein, glucose, urobilinogen, bilirubin, ketones, blood/erythrocytes, specific gravity, sediment, volume

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Towards the end of the treatment period, during Week 13 (on Day 84 am), each animal in the main and recovery groups was subjected to the functional observation battery, including qualitative assessment of the grip strength, and to measurements of the landing foot splay and fore/hind grip strength.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

IMMUNOTOXICOLOGY INVESTIGATION:
- T-cell dependent antibody response (TDAR) assay
- Lymphocyte subtyping

Statistics:

Data were collected using the software PROVANTIS v.7, or were recorded on the appropriate forms from the relevant SOPs of CiToxLAB Hungary Ltd., then tabulated using the software PROVANTIS v.7, Microsoft Office Word and/or Excel, as appropriate. Results of ELISA measurements were calculated using Ascent Software and Microsoft Excel®.

The statistical evaluation of the numerical data was performed with the program package SPSS PC+4.0 (SPSS Hungary Kft, Budapest).

The heterogeneity of variance between groups was checked by Bartlett's homogeneity of variance test. Where no significant heterogeneity was detected, a one-way analysis of variance was carried out. If the obtained result was positive, Duncan's Multiple Range test was used to assess the significance of inter-group differences. Where significant heterogeneity was found, the normal distribution of data was examined by Kolmogorov-Smirnov test. In case of abnormal distribution, the non-parametric method of Kruskal-Wallis One-Way analysis of variance was applied. If there was a positive result, the inter-group comparisons were performed using Mann-Whitney U-test. T-test was used in case of two groups’ comparison (Recovery groups).
The mean and standard deviations values were calculated.
No statistical analysis was carried out on food consumption data, due to small number of elements (2 cages in Low and Mid groups during treatment period and all groups during recovery period).

Statistical evaluation of results of lymphocyte subtyping measurements was performed by Principal Investigator using Citox software (version D.7).

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

There were no clinical signs or mortality related to the test item.

Mortality:

no mortality observed

Description (incidence):

There were no clinical signs or mortality related to the test item.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

There were no toxicologically significant changes in the animal behaviour, general physical condition, in the reactions to different type of stimuli in the control or treated groups.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

There were no test item related effects on food consumption. The average food consumption was comparable to the control in all treated groups.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No test item related changes compared to pre-treatment were noted at ophthalmoscopy examination in the Control and High dose Group 4 animals, during Week 13 (Day 85), therefore no examination of the lower dose groups and recovery groups was necessary.

Haematological findings:

no effects observed

Description (incidence and severity):

There were no test item related adverse effects at any dose level.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

There were no test item related adverse effects at any dose level.

Urinalysis findings:

no effects observed

Description (incidence and severity):

There were no test item related adverse effects at any dose level.

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

There were no toxicologically significant changes in the animal behaviour, general physical condition, in the reactions to different type of stimuli in the control or treated groups.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

The statistically significant changes after 90 days, including the increased relative liver weights in both sexes and kidney weights in females were considered to be test item related, however they were of low magnitude and were reversible.

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no macroscopic findings considered related to test item administration under the conditions of this study.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

At the highes dose minimal to mild changes were found in the liver and kidneys of females only. At the mid dose minimal changes were found in the liver (minimal periportal hepatocellular hypertrophy) of few females and were regarded as adaptive.

Details on results:

CLINICAL SIGNS AND MORTALITY
There were no clinical signs or mortality related to the test item.

BODY WEIGHT AND WEIGHT GAIN
The mean body weight and body weight gain of males and females in all experimental groups were comparable to the control throughout the treatment period. Minor variations were noted on occasion attaining statistical significance (e.g. slightly lower body weight gain values in Mid dose males on Week 12 or higher values in High dose females on Weeks 5 and 10) and were regarded as incidental and with no toxicological significance.
During the recovery period, the body weight and body weight gain values were comparable to the control in both males and females. A minor difference limited to one occasion was recorded for males on Week 17 (p <0.05) which was considered incidental.

OPHTHALMOSCOPIC EXAMINATION
No test item related changes compared to pre-treatment were noted at ophthalmoscopy examination in the Control and High dose Group 4 animals, during Week 13 (Day 85), therefore no examination of the lower dose groups and recovery groups was necessary.

HAEMATOLOGY
There were no test item related adverse effects at any dose level.

CLINICAL CHEMISTRY
Clinical chemistry evaluation did not reveal any obvious toxicity for test item following the 90-day treatment or recovery periods.

URINALYSIS
Clinical chemistry evaluation did not reveal any obvious toxicity for test item following the 90-day treatment or recovery periods.

NEUROBEHAVIOUR
There were no toxicologically significant changes in the animal behaviour, general physical condition, in the reactions to different type of stimuli in the control or treated groups.

ORGAN WEIGHTS
The statistically significant changes after 90 days, including the increased relative liver weights in both sexes and kidney weights in females were considered to be test item related, however they were of low magnitude and were reversible.
There were no biologically significant differences among groups in the weights of other organs measured, compared with control, although statistically significant variations were noted (i.e higher spleen and thymus weight, when adjusted for body weight and higher spleen weight when adjusted for brain weight in Mid dose females on Day 90, higher brain related thyroid/parathyroids weights in Mid dose males on Day 90). The values were within physiological range and were not considered to reflect an adverse effect.

GROSS PATHOLOGY
There were no macroscopic findings considered related to test item administration under the conditions of this study.

HISTOPATHOLOGY: NON-NEOPLASTIC
Test item-related microscopic findings were noted in the liver and kidney in the females at dose levels of 120 and 480 mg/kg/day.
At 480 mg/kg/day, hepatic changes were characterized as periportal hepatocellular hypertrophy, mixed cell infiltrate and proliferation of the Kupffer cells. These alterations correlated with minimal organ weight changes. Minimal hypertrophy was observed in 3 of 10 High dose females. Mixed cell infiltrate diffusely distributed in the sinusoidal space, was noted with minimal to mild degree in 4 of 10 High dose female rats. In addition, proliferated Kupffer cells (enlarged size/number) were associated with infiltrate in 1 of 4 altered female. The hepatic changes observed in the High dose were regarded to be adverse.

At 120 mg/kg/day, minimal hepatic changes were observed in 2 of 10 females, consisted of minimal periportal hepatocellular hypertrophy and were regarded as adaptive response. In 3 of 10 females minimal mixed cell infiltration was also observed. In two females this minimal infiltration was noted additionally to hepatocellular hypertrophy and in one female it was the only hepatic observation. Mixed cell infiltration may spontaneously occur in rats (ref. 4); therefore the causative role of the treatment is equivocal.

Renal changes were recorded in the cortical tubules. The degeneration of tubule epithelium (cytoplasmic vacuolation, cellular sloughing) associated with the presence of homogenous eosinophilic content (casts) filled tubular lumen was seen in 1 of 10 Mid dose and 2 of 10 High dose females. The degenerative changes altered tubular epithelium with minimal severity. Bilateral focal/multifocal distribution was present in High dose animals while unilateral/focal localization appeared in the Mid dose female. There was no evidence of the peritubular inflammatory response.
The renal changes at 480 mg/kg/day were regarded as adverse. Taking into account unilateral occurrence and minimal focal degree at 120 mg/kg/day, the finding was not regarded to be adverse.

Although minimal unilateral focal homogenous eosinophilic casts in the lumen of the cortical tubules were observed in 3/10 Low dose females, their microscopic feature was similar to minimal unilateral focal homogenous eosinophilic casts present in 1 of 10 Control female in recovery period. In addition, there was no damage to tubular epithelium or inflammatory reaction. Therefore, the casts seen in the Low dose group were considered to be without relationship to the treatment.

The spleen and thymus were examined closely in accordance with the Study Plan to clarify any potential immunotoxicity. Minimal extramedullary haematopoiesis in the spleen was present in 2/9 Control and 7 of 10 High dose males and 5 of 10 Control and 8 of 10 High dose females. There was no meaningful difference in these splenic observations between controls and treated rats, and they were considered to be a common background. In the thymus, minimal decrease of size/cellularity of the cortex/medulla in 1 of 10 female (4502) and 1 of 10 male (4003; associated with minimal prominent epithelial cords and tubules) from the High dose groups, were seen.

Decreased size/cellularity of cortical/medullary compartments was not associated with an increase of severity grade of lymphocyte apoptosis comparing to controls or inflammatory reaction. No notable reduction in thymic weight was detected in these two High dose animals. Therefore, it seems that thymic changes were not ascribed to the administration of the test item, but rather reflected individual stress conditions in these rats. It is concluded that there was no evidence for any immunotoxic effects in these tissues following a 90 day exposure of up to 480 mg/kg/d of the test item.

Following a 28-day treatment-free period, the recovery process was completed in the liver, however, effects of treatment were evident in the kidney.
In kidneys, mild bilateral or minimal unilateral multifocal tubular degeneration /regeneration with the presence of luminal homogenous eosinophilic casts was observed in 2 of 10 High Dose females. The tubules also had evidence of a regenerative process accompanied with increased tubule cells basophilia, transition of cell shape from flattened to cuboidal and/or mitosis.

In one of this female (4511), bilateral minimal glomerulonephritis as spontaneous change cannot be excluded since other inflammatory disorder, mild interstitial pneumonia affected all lobes of lungs was also observed in this animal, in addition to mild bile duct hyperplasia was observed, however, being a common background observation in the liver, was not considered to be test item related.

Other changes were without meaningful incidence and/or severity represented incidental or background observations without relationship to the treatment.


OTHER FINDINGS: IMMUNOTOXICOLOGY FINDINGS

T-CELL DEPENDENT ANTIBODY RESPONSE (TDAR) ASSAY
No statistically or biologically significant changes were detected in the anti-SRBC IgM level of the test item treated dose groups of male animals. Decreased anti-SRBC IgM levels compared to the negative control group were detected in the mid and low dose group of the female animals. However, no dose response was observed, and the observed values were statistically not different from negative control values of the male animals.

LYMPHOCYTE SUBTYPING
There were no test item effects on lymphocyte analysis that could be attributed to the treatment at any of the dose level up to and including 480 mg/kg/day.

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

480 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: 480 mg/kg bw/day is the highest tested dose

2

Dose descriptor:

NOEL

Effect level:

120 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

3

Dose descriptor:

NOAEL

Effect level:

120 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: based on microscopic changes in the liver and kidneys in females at 480 mg/kg bw/day

4

Dose descriptor:

NOEL

Effect level:

40 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

A daily oral (gavage) administration of 2,2’-ethylenedioxydiethyl bis(2-ethylhexanoate) to Wistar rats for 90 consecutive days at 40, 120 and 480 mg/kg/day was associated with the following findings. There were no toxicologically significant effects on clinical signs, ophthalmology or neurotoxicology endpoints. There were no effects on body weight, food intake, bone marrow cellularity, or haematology or urinalysis parameters. For clinical chemistry no adverse effect was noted, however, slight and reversible changes were noted in males (increased serum cholesterol and bile acids) and in females (decreased triglycerides). There were no adverse effects on organ weights or on macroscopic observations at necropsy. There were no effects on any immunotoxicology endpoints including lymphocyte subpopulation analysis or T-cell Dependent Antibody Response (TDAR) assay. At 480 mg/kg/day minimal to mild changes were found in the liver and kidneys of females only. Changes in the liver consisted of periportal hepatocellular hypertrophy and mixed cell infiltrate and proliferation of the Kupffer cells, correlated with slightly higher organ weight and were fully reversible during 28-day recovery period. The renal changes consisted of the minimal bilateral focal/multifocal degeneration of the epithelium of cortical tubules (cytoplasmic vacuolation, cellular sloughing) associated with the presence of eosinophilic casts in tubular lumen. Signs of recovery were observed in the cortical tubuli. A decreased performance was noticed during motor activity measurements in males dosed at 480 mg/kg/day, however the effect was reversible and not considered to be adverse. No other adverse effects were noted in males. At 120 mg/kg/day minimal changes were found in the liver (minimal periportal hepatocellular hypertrophy) of few females and were regarded as adaptive. In one female, unilateral focal degeneration of tubule epithelium with eosinophilic casts in tubular lumen was seen in kidney, but taking into account unilateral occurrence and minimal focal degree, the finding was not regarded to be adverse. No effects were observed for males. Treatment at 40mg/kg/day was not associated with any adverse effects or histopathological changes. In conclusion, the NOAEL of 2,2’-ethylenedioxydiethyl bis(2-ethylhexanoate) administered by oral gavage to Wistar rats for 90 consecutive days is considered to be 480mg/kg/day for males and 120mg/kg/day for females, based on microscopic changes in the liver and kidneys in females at 480 mg/kg/day. The NOEL is 120 mg/kg/day for males and 40 mg/kg/day for females. No immunotoxicity was detected at any dose level up to and including 480 mg/kg/day.

Executive summary:

The objective of this study was to obtain information on the toxicity of 2,2’- ethylenedioxydiethyl bis(2-ethylhexanoate) when administered daily for 90 days by oral gavage to the Wistar rat at 3 dose levels.

Doses of 40, 120, and 480 mg/kg /day were administered to male and female Wistar rats according to the experimental design presented in the following table.

Table 1: Experimental design

Group designation	Dose Level (mg/kg/day)	Conc (mg/mL)	Dose volume (mL/kg bw/day)	Number of Animals
				Main study				Satellite groups
				Males		Females		Males	Females
				Main	Recovery	Main	Recovery
Control	0	0	2.5	10	10	10	10	10	10
Low Dose	40	16		10	-	10	-	10	10
Mid Dose	120	48		10	-	10	-	10	10
High Dose	480	192		10	10	10	10	10	10

Rats assigned to Recovery groups, following the completion of 90-day treatment period were kept for a 28-Day observation period.

Satellite groups were assigned to immuntoxicology T-cell Dependent Antibody Response (TDAR) investigation.

An additional group of ten male and ten female Wistar rats served as positive control for TDAR investigation (animals were

treated with cyclophosphamide, a known immunosuppressant, via intraperitoneal injection).

The test item was formulated in propylene glycol containing 1% Tween 80 and the control group was treated with the vehicle only. The first day of the treatment was Day 0 for all animals.

During the study, observations for mortality and clinical signs were performed daily, detailed clinical examination, body weight and food consumption measurements were performed at weekly intervals.

Ophthalmoscopy and neurological assessment including a functional observation battery (FOB) and measurements of the landing foot splay, grip strength and motor activity were performed during the last week of treatment. A motor activity measurement was repeated for males groups during the last week the recovery.

Clinical pathology examinations (haematology, clinical chemistry and urinalysis) were conducted prior to necropsy following the end of the treatment and recovery periods (Days 90 and 118), followed by necropsy with macroscopic examination and selected organ weight measurements.

Full histopathology was performed for Groups 1 (Control) and 4 (High dose); in addition, the affected organs (kidneys and liver) from females of the Low and Mid dose and Recovery groups were also examined. Organs showing macroscopic findings from any animal of any group were also examined microscopically.

Analysis of test item formulations for concentration and homogeneity was performed four times during the treatment period, using a validated GC method. All formulations were found to be in the range of 90 to 102% of nominal concentrations and were homogeneous. No test item was detected in the control samples. Based on these results, the test item formulations were considered suitable for the study purposes.

RESULTS

No mortality or clinical signs considered related to test item was observed during the study. There were no toxicologically significant changes in the animal behaviour, general physical condition, in the reactions to different type of stimuli in the control or treated groups. No test item related effects were observed in the landing foot splay test or grip strength measurements. In motor activity measurements, the total travelled distance was slightly lower (by approximately 22%), in males at 480 mg/kg/day. The average velocity and total time moving fast were also slightly lower, than control mean. As the patterns of activity were comparable with those of the control and the individual values were within the physiological range, therefore the effect was not regarded as adverse. Following the 28-day recovery period, all parameters in the motor activity test examined in males at 480 mg/kg/day, were comparable with controls.

The oestrus cycle of the females was undisturbed by the treatment with the test item.

No test item related changes compared to pre-treatment were noted at ophthalmoscopy examination.

There were no test item related effects on body weight and body weight gain or food consumption.

There were no test item related adverse effects in haematology, blood clotting, bone marrow cellularity, clinical chemistry or urinalysis parameters at any dose level.

There were no macroscopic findings considered related to test item administration.

For organ weight, minimal differences were measured on Day 90 in females for liver and kidneys at 480 mg/kg/day and for liver at 120 mg/kg/day. The absolute and relative weights of liver were higher than control means by approximately 8-10% (Mid dose) and 8-12% (High dose). The changes were not considered adverse.

Microscopically a minimal periportal hepatocellular hypertrophy and minimal to mild periportal mixed cell infiltrate were seen in the liver in 2-3 of 10 Mid Dose and 3-4 of 10 High Dose females, occasionally accompanied by proliferation of the Kupffer cells (1 of 10 High Dose females). The overall microscopic picture in the High dose was classified as adverse, while findings in the Mid dose rather as adaptive change.

High dose females had also slightly higher weights of kidneys (no more than 11%). Microscopically in the kidneys, minimal degeneration of epithelium of cortical tubule (cytoplasmic vacuolation, cellular sloughing) associated with the presence of homogenous eosinophilic content (casts) filled tubular lumen was seen in 2 of 10 High dose females. Although minimal focal degeneration and eosinophilic content was observed in right kidney in 1 of 10 Mid dose female, but taking into account unilateral occurrence and minimal focal degree, the finding was not regarded as adverse.

Following a 28 -day treatment-free period, complete recovery was observed in the liver and signs of the recovery were detected in the kidney. In kidneys, mild bilateral or minimal unilateral multifocal tubular degeneration/regeneration with the presence of luminal homogenous eosinophilic casts was observed in 2 of 10 High Dose females. The tubules also underwent regenerative process accompanied with increased tubule cells basophilia, transition of cell shape from flattened to cuboidal and/or mitosis.

During Immuntoxicology investigation, in a T-cell Dependent Antibody Response (TDAR) assay, no changes were detected in males. Decreased anti-SRBC IgM levels compared to the negative control group were detected in the mid and low dose group of the females. However, no dose response was observed, and the observed values were statistically not different from negative control values.

There were no test item effects on lymphocyte subpopulation analysis that could be attributed to the treatment at any of the dose level up to and including 480 mg/kg/day. Minor differences between groups were observed which were considered to represent normal variation and of no toxicological or biological relevance.

CONCLUSION

A daily oral (gavage) administration of 2,2’-ethylenedioxydiethyl bis(2-ethylhexanoate) to Wistar rats for 90 consecutive days at 40, 120 and 480 mg/kg/day was associated with the following findings.

There were no toxicologically significant effects on clinical signs, ophthalmology, body weight, food intake, haematology, blood clotting, bone marrow cellularity, clinical chemistry or urinalysis parameters.

There were no adverse effects on organ weights or on macroscopic observations at necropsy. There were no treatment related effects on any immunotoxicology endpoints including lymphocyte subpopulation analysis or T-cell Dependent Antibody Response (TDAR) assay.

At 480 mg/kg/day minimal to mild changes were found in the liver and kidneys of females only. Changes in the liver consisted of periportal hepatocellular hypertrophy and mixed cell infiltrate and proliferation of the Kupffer cells, correlated with slightly higher organ weight and were fully reversible during 28-day recovery period. The renal changes consisted of the minimal bilateral focal/multifocal degeneration of the epithelium of cortical tubules (cytoplasmic vacuolation, cellular sloughing) Associated with the presence of eosinophilic casts in tubular lumen. Signs of recovery were observed in the cortical tubuli.

A decreased performance was noticed during motor activity measurements in males dosed at 480 mg/kg/day, however the effect was reversible and not considered to be adverse. No other adverse effects were noted in males.

At 120 mg/kg/day minimal changes were found in the liver (minimal periportal hepatocellular hypertrophy) of few females and were regarded as adaptive. In one female, unilateral focal degeneration of tubule epithelium with eosinophilic casts in tubular lumen was seen in kidney, but taking into account unilateral occurrence and minimal focal degree, the finding was not regarded to be adverse. No effects were observed for males.

Treatment at 40mg/kg/day was not associated with any adverse effects or histopathological changes. In conclusion, the NOAEL of 2,2’-ethylenedioxydiethyl bis(2-ethylhexanoate) administered by oral gavage to Wistar rats for 90 consecutive days is considered to be 480 mg/kg/day for males and 120 mg/kg/day for females, based on microscopic changes in the liver and kidneys in females at 480 mg/kg/day. The NOEL is 120 mg/kg/day for males and 40 mg/kg/day for females. No immunotoxicity was detected at any dose level up to and including 480 mg/kg/day.