2,2,2,4,4,4,4-heptakis[(2-ethylhexanoyl)oxy]cyclodimolybdoxan-2-yl 2-ethylhexanoate

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This study was conducted according to GLP, but individual data are not presented in the paper. The study is essentially in accordance with OECD Guideline 408, except that only 5 animals per sex group were assessed for haemotology and clinical chemistry, and no neurotixicology assessment was conducted (this was in line with the guideline at the time of the study being conducted).

Data source

Reference

Reference Type:

publication

Title:

2-Ethylhexanoic Acid: Subchronic Oral Toxicity Studies in the Rat and Mouse

Author:

Juberg, D.R., David, R.M., Katz, G.V., Bernard, L.G., Gordon, D.R., Vlaovic, M.S., and Topping, D.C.

Year:

1998

Bibliographic source:

Food and Chemical Toxicology 36, 429-436

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OTS 795.2600 (Subchronic Oral Toxicity Test)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-ethylhexanoic acid

EC Number:

205-743-6

EC Name:

2-ethylhexanoic acid

Cas Number:

149-57-5

Molecular formula:

C8H16O2

IUPAC Name:

2-ethylhexanoic acid

Details on test material:

2-ethylhexanoic acid was obtained from Eastman Chemical Company (Kingsport, TN, USA). The purity of the test item was determined to be 99.9% (±0.05%) and the mass spectrum was consistent with the structure of 2-ethylhexanoic acid.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Wilmington, MA
- Age at study initiation: 6 weeks
- Diet (e.g. ad libitum): Agway Prolab Animal Diet (RMH 3200), certified ground chow; ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 2 weeks

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

The test substance was mixed with ground certified chow using a Hobart cafeteria-type food mixer (Model M-802) to yield target concentrations of 0.0, 0.1, 0.5 and 1.5 % (w/w) of the test item. Diets were prepared monthly and the concentrations of test diets were verified analytically.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

No details available.

Duration of treatment / exposure:

91-93 days

Frequency of treatment:

7 days per week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 0.1, 0.5 and 1.5 %
Basis:
nominal in diet

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 61, 303 and 917 mg/kg/day for male rats; 0, 71, 360 and 1068 mg/kg/day for females
Basis:
other: actual dose

No. of animals per sex per dose:

10

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: based on a 14-day feeding study in rats
- Post-exposure recovery period in satellite groups: 28-29 days

Positive control:

Not incluced

Examinations

Observations and examinations performed and frequency:

CLINICAL OBSERVATIONS: Yes
- Detailed observations: on the mornings of body weight measurement.
- Cage side observations: every workday afternoon and on mornings on which body weights were not collected. Animals were checked for mortality on weekends.

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 4, 7, and at least once weekly thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Feed weights (g) were collected on days 4, 7, and at least once weekly thereafter.

OPHTHALMOSCOPIC EXAMINATION: Yes, using an indirect ophthalmoscope after dilation of the pupils with 1% Mydriacyl.
All rats were examinde prior to the start of the study. During the last week of exposure, five male and five female non-recovery animals from each dose level were examined.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at necropsy
- Anaesthetic used for blood collection: Yes (CO2 anaesthesia)
- Animals fasted: overnight
- How many animals: five animals per sex, per dose.
- Parameters: Non-recovery groups: hemoglobin concentration, hematocrit, red blood cell count, white blood cell count, differential white blood cell count, platelet count, red blood cell indices, prothrombin time, and examination of the blood smears for cellular morphology. Recovery groups: hemoglobin concentration, hematocrit, red blood cell count, white blood cell count, platelet count, red blood cell indices.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at necropsy
- Animals fasted: overnight
- How many animals: five animals per sex per dose
- Parameters: Non-recovery groups: aspartate aminotransferase, alanine aminotransferase, total bilirubin, total protein, albumin, creatinine, urea nitrogen, glucose, gamma glutamyl transpeptidase, triglycerides, cholesterol, sodium, potassium, chloride, calcium and phosphorus. Recovery groups: albumin, urea nitrogen, triglycerides, cholesterol.

URINALYSIS: Yes
In the week prior to termination of exposure, five males and five females from each dose group were place in metabolism cages for 24-hour urine collections. Parameters: Non recovery-groups: specific gravity, osmolality, volume, glucose, bilirubin, ketones, blood, protein, urobilinogen, nitrite, leukocytes and pH. Recovery-groups: specific gravity, osmolality and volume.

Sacrifice and pathology:

Organ weights: liver, kidneys, adrenal glands, testes, ovaries, brain.
Histopathology: all non-recovery high-dose and control animals: trachea, lungs, heart, aorta, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, pancreas, liver, salivary glands, kidneys, urinary bladder, pituitary gland, adrenal glands, thyroid glands, parathyroid glands, thymus, spleen, mesenteric lymph nodes, bone marrow (femoral), brain (including sections of medulla/pons, cerebellar cortex, and cerebral cortex), sciatic nerve, quadriceps femoris, testes, ovaries, vagina, uterus, fallopian tubes, sternum with bone marrow, and gross lesions.
The liver, kidneys, lungs, target organs, and gross lesions for animals from all dose levels were examined.
Because no signs of toxicity or target organ involvement was observed, no histopathology was performed on cervical/mid-thoracic/lumbar spinal cord, epididymides, male accessory sex glands, male mammary gland, female mammary gland, femur (including articular surface), skin, and exorbital lachrymal glands.
For recovery animals, histopathology was performed on the liver, kidneys, lungs, and gross lesions.

Other examinations:

Sections of the liver were prepared for electron microscopy and stored for possible future examination.

Statistics:

Means were calculated for body weight, feed consumption, and organ weights. Numerical data were evaluated using Bartlett's test, one-way ANOVA, and Duncan's multiple range test. Feed consumption was not analyzed statistically because animals were group housed.

Results and discussion

Results of examinations

Details on results:

CLINICAL SIGNS AND MORTALITY
- Urine-soaked inguinal, abdonimal, scrotal, and/or thigh haircoats, discolored yellow, and/or unkempt: observed periodically during treatment in males and frequently in females, at all dose levels.
No mortality occured during the study.

BODY WEIGHT AND WEIGHT GAIN
A reduced mean body weight was observed in males and females of the high-dose group (8% and 10% below control weights at necropsy, respectively). Because of a caging problem, decreased body weights were observed in the mid-dose females on day 21. No effects on body weights were observed in the other groups.
During the recovery phase, the rate of body weight gain for the high-dose animals increased, but was still slightly below control level at study termination.

FOOD CONSUMPTION
During the first few days of the study, average feed consumption was moderately reduced in the high-dose group. Average consumption from day 4 to the end of the treatment period for the 1.5% males and females was 3.5 and 8.5% (non-recovery) and 4.7 and 9.5% (recovery) lower than controls, respectively. During the recovery period, average food intake was 3.7% and 0.8% higher than controles for the males and females of the exposed groups, respectively. Feed consumption was comparable to control levels in the low- and mid-dose groups.

HAEMATOLOGY
Mean corpuscular hemoglobin (MCH) was very slightly decreased in males of the mid- and high-dose groups. Females of the high-dose group had lower values for MCH and mean corpuscular volume (MCV) and the mid-dose females had a decreased mean hemoglobin concentration. Slight poikilocytosis was observed at all dose levels for males and at the mid- and high-dose for the females. Additional erythrocyt changes consisted of spherocytosis (two high-dose males), microcytosis (one high-dose female) and decreased polychromasia (in high-dose males and control, low- and high-dose females).
In the high-dose recovery group, males showed a lower MCH and females a decreased MCV, relative to controls.

CLINICAL CHEMISTRY
Cholesterol levels were increased in a dose-dependent manner for the males and the high-dose males showed elevated levels of urea, nitrogen and albumin. All anomalies returned to control level after the recovery period.

URINALYSIS
Urine volumes were decreased at all treatment levels in females and specific gravity levels were slightly increased in the high-dose females. These effects are probably due to chance or are related to decreased fee inatke in the high-dose group. No abnormalities were observed at the end of the recovery period.

ORGAN WEIGHTS
- Absolute liver weight and relative liver/body and liver/brain weights were increased for the mid- and high-dose animals in a dose-dependent manner. For the high-dose males, the relative liver/body remained elevated after the recovery period.
- Relative kidney/body weights were slightly increased for the high-dose males and females and for the mid-dose females. Relative kidney/brain weights were slightly increased for the mid- and high-dose females. Absolute kidney weights were slightly decreased in the high-dose recovery animals. The observed kidney effects are most likely a reflection of the decreased body weights.
- The differences in brain weights (viz. decreased absolute and increased relative weights at the high dose) are those expected because of differences in body weight and indicate sparing of the brain during growth inhibition.
- Relative testes weights were increased for the mid- and high-dose males (also in the recovery group) and reflect slightly decreased body weights, rather than target organs effects.

HISTOPATHOLOGY: NON-NEOPLASTIC
Hepatocyte hypertrophy with dose-dependent severity, primarily located in the portal area, was observed in all animals of the high-dose group and in males of the mid-dose group. The hypertrophy was characterized by an increase in the cell size with compression of the adjoining sinusoidal spaces. Furthermore, a decreased incidence of small cytoplasmic vacuoles was observed in a dose-dependent manner. No treatment-related effects were observed in the recovery group.
The minimal hyperplasia of bile ducts, observed in the control and high-dose recovery group, was considered not to be biologically significant.

Effect levels

Dose descriptor:

NOAEL

Effect level:

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

Sex:

male/female

Basis for effect level:

other: Reduced feed consumption and decreased rate of body weight gain

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

The liver enlargement was considered to be primarily an adaptive change rather than a toxic effect.

Applicant's summary and conclusion

Conclusions:

The study determined the NOAEL of 2-ethylhexanoic acid to rats to be 300 mg/kg bw/day.