Isooctyl acetate

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

8 April 1985 - 11 July 1985

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Isooctyl acetate

EC Number:

250-701-2

EC Name:

Isooctyl acetate

Cas Number:

31565-19-2

Molecular formula:

C10H20O2

IUPAC Name:

Acetic acid, isooctyl ester

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 2

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories Inc
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation:6-8 weeks
- Weight at study initiation:Males (167-203 g); Females (144-178 g)
- Fasting period before study: No data
- Housing: Individual cages with suspended stainless steel floor
- Diet (e.g. ad libitum): Purina Certified Roden Chow ad libitum
- Water (e.g. ad libitum): Automatic watering system ad libitum
- Acclimation period: 13 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24 °C
- Humidity (%): 40-70 %
- Photoperiod (hrs dark / hrs light): 12 hours light/dark

IN-LIFE DATES: From: 8 April 1985 To: 11 July 1995

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

The dose administered was calculated by dividing the dose level by the density (0.89 g/ml) to arrive at the dose volume. The
animals body weight was then multiplied by the dose volume to arrive at the animal's actual dose. The amount of test material
administered to each animal was recalculated weekly based on the most recent body weight. Control group animals received 1.0
ml/kg of distilled water.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

5 days per week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

500 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

20

Control animals:

yes, concurrent no treatment

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: morning and afternoon

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at sacrifice

BODY WEIGHT: Yes
- Time schedule for examinations: day 0 then weekly thereafter

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Prior to termination
- Dose groups that were examined: All

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Prior to study and at sacrifice
- Anaesthetic used for blood collection: Not specified
- Animals fasted: No
- How many animals: 5 per sex per dose

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at scheduled sacrifice
- Animals fasted: Not specified
- How many animals: 160

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

IMMUNOLOGY: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes

HISTOPATHOLOGY: Yes

Statistics:

Mean hematology parameters, mean serum chemistry parameters, mean organ weights, mean organ to body weight ratios, mean body weights, by weighing period and mean food consumption underwent statistical evaluation. Comparisons were limited to within sex analysis.
Statistical evaluation of equality of means was done by an appropriate one way analysis of variance and a test for ordered response in the dose
groups. First, Bartlett's test was performed to determine if the dose groups have equal variance. If the variances are equal the
testing was done using parametric methods, otherwise nonparametric techniques were used.
For the parametric procedures, a standard one way ANOVA using the F distribution to assess significance was used. If significant differences among the means were indicated, Dunnett's test was used to determine which treatment groups differ significantly from control.
For the nonparametric procedures the test of equality of means was performed using the Kruskal-Wallis test. If significant differences among the means were indicated, Dunn's Summed Rank test was used to determine which treatment group differ significantly from control. In addition to the Kruskal-Wallis test, Jonckheere's test for monotonic trend in the dose response was performed.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Alopecia and scabs, predominantly on the forelegs and snout areas, were observed in the higher dose groups. This suggests that the test material was irritating to some extent, and that the animals spent some amount of time cleaning the mouth and snout area.
An increased incidence of urinary staining (normal color) was observed in the high dose animals, when compared to controls and other dosed groups.
Urinary staining was considered to be a. mild treatment related effect.

Mortality:

mortality observed, non-treatment-related

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Mean body weights for the high dose males and females were generally lower than body weight values of the other test groups. There were three occasional instances where the body weights were statistically significantly lower, but the random appearance of these differences suggested that the effect, though apparently related to treatment, was minimal or borderline.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

Mean food consumption values for the high dose animals in general were slightly lower than control values, and the other dose levels. Singular instances of statistically significant differences suggested that this finding may have been a borderline or minimal treatment related effect.
There was a sharp decrease in food consumption in the males of all four test groups from Day 35 to Day 42. Such an effect was not observed in females and was not reflected in the body weigh measurements. Thus, although the reason for this sharp decrease could not be clearly identified, it was not considered to have been related to treatment with MRD-83-303.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

Singular instances of statistical significance were observed in albumin (high dose males), creatinine (high dose males), potassium (high dose females), and alanine aminotransferase (high dose females), but none of theses clearly indicated a treatment related effect.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

Urinary staining observed in the high dose group

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Absolute and relative liver weights in dosed males and females were elevated above control weights in a linear dose related manner. The differences in relative liver weight became statistically significant in the mid dose and high dose groups. This effect was considered to be treatment related, but was considered to be a physiological adaptation to the test material rather than a toxic effect on the liver.
Absolute and relative kidney weight in the mid dose and high dose males and females were elevated above control values, with the difference in high dose relative kidney weights becoming statistically significant. The increases were considered to be treatment related but there was no correlation with gross necropsy results to suggest that this increase in weight was due to a toxic effect on the kidney.
All other absolute and relative organ weights were comparable to control.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

An increased incidence of lung abnormalities (4 control, 6 low dose, 12 mid dose, 14 high dose). This observation were considered to be related to treatment.

Neuropathological findings:

not examined

Histopathological findings: neoplastic:

not specified

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

gross pathology

Target system / organ toxicity

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

500 mg/kg bw/day (nominal)

System:

respiratory system: upper respiratory tract

Organ:

lungs

Treatment related:

yes

Dose response relationship:

not specified

Relevant for humans:

not specified

Applicant's summary and conclusion

Conclusions:

In-life observations indicated slight irritation of the mouth by the test material, coincident with an increased incidence of scabs on the snout and forepaws. Slight to moderate urinary staining was observed in the higher dose animals, suggesting a mild treatment related effect. Liver and kidney weights were both increased in a dose related manner but these were not accompanied by abnormal gross pathology or clinical chemistry parameters. Such elevated organ weight are therefore considered to be due to physiological adaptation rather than due to a toxicolgcal effect. At the terminal necropsy, urinary staining was considered to be treatment related, as was an increased incidence of lung abnormalities in the mid dose and high dose rats.

Executive summary:

The objective of this study was to evaluate the effects of MRD-83-303 when administered by the oral route, via gavage, 5 days per week for at least 13 weeks. One hundred sixty Sprague-Dawley rats were divided in 4 groups of 20 males and 20 females each. Group I was used as a control which received distilled water. Groups II, III and IV received doses of 0.1, 0.5 and 1.0 grams of test material/kg of body weight respectively.

Observations were made as to the nature, onset, severity and duration of toxicological signs once a day for the duration of the study. Body weights were recorded prior to dosing, at dosing initiation, and weekly thereafter during the test period. Food consumption was measured weekly during the course of the study. Serum chemistry and hematology studies were performed on all animals at time of scheduled necropsy.

Five per sex per group of randomly selected test animals were sacrificed and bled (abdominal aorta) after 45 days of dosing. A complete necropsy was performed. Livers only were collected, weighed and preserved.

After at least 13 weeks of oral administration of MRD-83-303, during a 3 day period, all surviving animals were weighed, anesthetized by methoxyfluorane, and blood samples were collected from the abdominal aorta. Animals were killed by exsanguination. A necropsy was performed and required organs and tissues were collected and weighed.

One animal died prematurely (Day 15), but this was not considered to be treatment related.

In-life observations indicated slight irritation of the mouth by the test material, coincident with an increased incidence of scabs on the snout and forepaws. Slight to moderate urinary staining was observed in the higher dose animals, suggesting a mild treatment related effect.

Body weights and food consumption values were slightly depressed in the high dose animals, suggesting borderline treatment related effects.

Liver weights of all treated rats were elevated in a dose-related manner at both the interim and terminal necropsy intervals, but the increase in weight was not accompanied by abnormal necropsy observations or elevated serum chemistry values. Thus, elevated liver weights were considered to be the result of a physiological adaptation to the test material rather than a toxic effect on the liver.

Kidney weights of mid-dose and high-dose animals were elevated at the terminal sacrifice, but like the liver weights, were not considered to represent a toxic effect on the kidney.

There were no biologically significant differences between control and treated rats at either sacrifice interval for hematology or serum chemistry parameters. Singular instances of statistical significance were not considered to be treatment related.

Necropsy observations indicated no treatment related effects at the interim sacrifice, except for urinary staining in the high dose animals. At the terminal necropsy, urinary staining was again considered to be treatment related, as was an increased incidence of lung abnormalities in the mid dose and high dose rats. Pretest and terminal ophthalmology examinations did not reveal any treatment related effects.

Hematology and necropsy parameters of the pretest animals were normal and unremarkable.