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Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2006
Report date:
2006

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

Constituent 1
Chemical structure
Reference substance name:
3-methyl-4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-buten-2-one
EC Number:
204-846-3
EC Name:
3-methyl-4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-buten-2-one
Cas Number:
127-51-5
Molecular formula:
C14H22O
IUPAC Name:
3-methyl-4-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-2-one
Details on test material:
- Sample No.: 929473

Test animals

Species:
rat
Strain:
other: Sprague-Dawley Crl:CD(SD)IGS BR
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Age at study initiation: 6 - 8 w
- Weight at study initiation: male: 131 - 172 g; female: 122 - 155 g
- Housing: in groups of three or four by sex in polypropylene grid-floor cages suspended over trays lined with absorbent paper
- Diet (e.g. ad libitum): free access, pelleted diet (Rodent 5LF2 (Certified) Diet)
- Water (e.g. ad libitum): free access, drinking water was supplied from polycarbonate bottles attached to the cage
- Acclimation period: 6 d


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 2
- Humidity (%): 55 +/- 15
- Air changes (per hr): > 15x
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
90 days
Frequency of treatment:
daily
Doses / concentrationsopen allclose all
Dose / conc.:
5 mg/kg bw/day (actual dose received)
Dose / conc.:
30 mg/kg bw/day (actual dose received)
Dose / conc.:
500 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10
Control animals:
yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes

BODY WEIGHT: Yes

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes

OPHTHALMOSCOPIC EXAMINATION: Yes
- Dose groups that were examined: control and high dose (500 mg/kg bw) group

HAEMATOLOGY: Yes
- Time schedule for collection of blood: end of study

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: end of study

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations:prior to start of study, then weekly
- Battery of functions tested: sensory activity during week 12

OTHER:
- All animals were examined for overt signs of toxicity, ill-health or behavioural changes immediately before dosing and one and five hours after dosing during the working week.
- Animals were observed immedately before dosing and one hour after dosing at weekends. Prior to the start of treatment and at weekly intervals thereafter, all animals were observed for signs of functional/behavioural toxicity.
-Functional performance tests were also performed on all animals during week 12, together with an assessment of sensory reactivity to different stimuli.
- Clinical signs, functional observations, bodyweight development and food and water consumption were monitored during the study.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes, of selected tissues
Statistics:
Statistical analyses were performed.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No adverse effect on bodyweight development was detected.
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
no effects observed
Ophthalmological findings:
no effects observed
Description (incidence and severity):
No treatment related changes
Behaviour (functional findings):
not examined
Description (incidence and severity):
No toxicologically significant effects in organ weights were detected
Gross pathological findings:
no effects observed
Neuropathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed

Effect levels

open allclose all
Key result
Dose descriptor:
LOAEL
Effect level:
500 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
NOAEL
Effect level:
500 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
other: highest dose tested, some effects observed that were considered adaptative in nature and non-adverse.
Dose descriptor:
NOAEL
Effect level:
30 mg/kg bw/day (nominal)
Based on:
other: effects at 30 mg/kg bw/day in males concluded to be a well documented change that is peculiar to the male rat in response to treatment with some hydrocarbons.
Sex:
male
Basis for effect level:
histopathology: non-neoplastic
Remarks on result:
other: effects at 30 mg/kg bw/day in males concluded to be a well documented change that is peculiar to the male rat in response to treatment with some hydrocarbons. As such, only the effects observed at 500 mg/kg bw/day were taken into account by the authors.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

The oral administration of the test material to rats for a period of ninety consecutive days at dose levels of 5, 30 and 500 mg/kg/day resulted in treatment related effects in males at 500 and 30 mg/kg/day and in females at 500 mg/kg/day. The No Observed Effect Level (NOEL) was considered to be 30 mg/kg/day for females and 5 mg/kg/day for males.

5 mg/kg no effects, reported No Effect Concentration
- There were no deaths. - No clinically observable signs of toxicity were detected in test or control animals throughout the study period. - There were no treatment-related changes in the behavioural parameters measured. - There were no treatment-related changes in the functional performance parameters measured. - There were no treatment-related changes in sensory reactivity. - No adverse effect on bodyweight development was detected. - No adverse effect on dietary intake or food efficiency was detected. No intergroup differences in water consumption were detected. - No treatment-related ocular effects were observed. - No treatment-related haematology changes were detected. - No treatment-related blood chemistry effects were detected. - No toxicologically significant effects in organ weights were detected. - At necropsy, no macroscopic abnormalities were detected. The no observed effect concentration of the test material in corn oil for males was 5 mg/kg/day.
30 mg/kg no observed adverse effect level, no effects, reported No Effect Concentration
- There were no deaths. - No clinically observable signs of toxicity were detected in test or control animals throughout the study period. - There were no treatment-related changes in the behavioural parameters measured. - There were no treatment-related changes in the functional performance parameters measured. - There were no treatment-related changes in sensory reactivity. - No adverse effect on bodyweight development was detected. - No adverse effect on dietary intake or food efficiency was detected. - No intergroup differences in water consumption were detected. - No treatment-related ocular effects were observed. - No treatment-related haematology changes were detected. - No treatment-related blood chemistry effects were detected. - No toxicologically significant effects in organ weights were detected. - At necropsy, no macroscopic abnormalities were detected. The following treatment-related changes were detected: - A greater incidence of higher severity grades of globular accumulations of eosinophilic material were observed in the tubular epithelium of 5/10 (minimal effects) and 4/10 (slight effects) males treated at this dose level (p0.05). Authors stated that this finding is consistent with the presence of hydrocarbon nephropathy, which results from the excessive accumulation of alpha-2-microglobulin in renal proximal tubular epithelial cells. Alpha-2-microglobulin is found only in the proximal tubular epithelium of adult male rats. - One male rat treated at this dose level exhibited associated higher grades of tubular basophilia. The no observed effect concentration of the test material in corn oil for females was 30 mg/kg/day. Authors stated that the kidney changes identified histopathologically were consistent with well documented changes that are peculiar to the male rat in response to treatment with some hydrocarbons. This effect may not be indicative of a hazard to human health and for the purposes of hazard evaluation the no observed adverse effect level for males should be regarded as 30 mg/kg/day.
 500 mg/kg bone marrow effects, liver
   - There were no deaths. - No clinically observable signs of toxicity were detected in test or control animals throughout the study period. - There were no treatment-related changes in the behavioural parameters measured. - There were no treatment-related changes in the functional performance parameters measured. - There were no treatment-related changes in sensory reactivity. - No adverse effect on bodyweight development was detected. - No adverse effect on dietary intake or food efficiency was detected. - No intergroup differences in water consumption were detected. No treatment-related ocular effects were observed. - No treatment-related haematology changes were detected. - No treatment-related blood chemistry effects were detected. - No toxicologically significant effects in organ weights were detected. - At necropsy, no macroscopic abnormalities were detected. The following treatment-related changes were detected: - Hepatocyte enlargement, centrilobular or generalised, was observed in relation to treatment for 4/10 (minimal effects) males and 9/10 (minimal effects) females treated at this dose level (p0.05 for males; p0.001 for females). Authors stated that hepatocyte enlargement is commonly observed in the rodent liver following the administration of xenobiotics and in the absence of associated degenerative changes may be interpreted as adaptive in nature. - A greater incidence of higher severity grades of globular accumulations of eosinophilic material were observed in the tubular epithelium of 3/10 (minimal effects), 5/10 (slight effects) and 1/10 (moderate effects) males treated at this dose level (p0.01). Authors stated that this finding is consistent with the presence of hydrocarbon nephropathy, which results from the excessive accumulation of alpha-2-microglobulin in renal proximal tubular epithelial cells. Alpha-2-microglobulin is found only in the proximal tubular epithelium of adult male rats. - Two male rats treated at this dose level exhibited associated higher grades of tubular basophilia. - In the thyroid, a higher incidence of follicular cell hypertrophy was seen in relation to treatment for 7/10 (minimal effects) males at this dose level (p0.01). - A higher incidence of lower grades of severity of adipose infiltration of the bone marrow, indicative of marrow hyperplasia, was observed in relation to treatment for 7/10 (minimal effects) and 3/10 (slight) males treated at this dose level (p0.01).

Applicant's summary and conclusion

Conclusions:
In this oral subchronic study in rats performed with the test item alpha-methylionone at doses 5, 30 and 500 mg/kg bw/day, the NOAELoral was found to be 30mg/kg bw/d for males and 500mg/kg bw/day for females.
Executive summary:

A study was conducted to investigate the systemic toxicity of the test material. The test material was administered by gavage to three groups, each of ten male and ten female Sprague-Dawley Crl:CD(SD)IGS BR strain rats for 90 consecutive days. A control group of ten males and ten females was dosed with the vehicle alone (corn oil). The animals were acclimatised for 6 days. At the start of treatement the males weighed 131 to 172 grams and the females weighed 122 to 155 grams. The animals were approximately 6-8 weeks old. Animals were housed in groups of three or four by sex in polypropylene grid-floor cages suspended over trays lined with absorbent paper. The animals were allowed free access to food and water. A pelleted diet (Rodent 5LF2 (Certified) Diet) was used. Mains drinking water was supplied from polycarbonate bottles attached to the cage. The animals were housed in a single air-conditioned room with an air exchange rate of at least 15 air changes per hour and the low intensity lighting was controlled to give twelve hours continuous light and twelve hours darkness. The temperature and relative humidity were set to achieve target values of 21 +/- 2 C and 55 +/- 15%, respectively. Dose levels were 5, 30 and 500 mg/kg/day at a volume of 4 ml/kg. All animals were examined for overt signs of toxicity, ill-health or behavioural changes immediately before dosing and one and five hours after dosing during the working week. Animals were observed immedately before dosing and one hour after dosing at weekends. Prior to the start of treatment and at weekly intervals thereafter, all animals were observed for signs of functional/behavioural toxicity. Functional performance tests were also performed on all animals during Week 12, together with an assessment of sensory reactivity to different stimuli. Clinical signs, functional observations, bodyweight development and food and water consumption were monitored during the study. Haematology and blood chemistry were evaluated for all animals at the end of the study. Ophthalmosscopic examination was also performed on control and high dose animals (500 mg/kg). All animals were subjected to gross necropsy examination and histopathological evaluation of selected tissues was performed Statistical analyses were performed.

There were no unscheduled death and no clinical sings of toxicity observed. No adverse effects on bodyweight, dietary intake or food efficiency and treatment-related haematology changes were detected. A statistically significant increase in liver and kidney weights both absolute and relative was observed in animals treated with 500 mg/kg/day and a significant increase in plasma creatinine, total protein and cholesterol were also observed in high-dose animals. Histopathology revealed an enlargement of hepatocytes in the liver (generally regarded as adaptive in nature) of animals treated with 500 mg/kg/day. Males treated with 500 mg/kg/day also showed a significant increase in spleen weight and in plasma albumin. No abnormalities were observed at necropsy. A greater incidence of globular accumulations of eosinophilic material in the kidney’s tubular epithelium was noted in males treated with 30 and 500 mg/kg/day and a higher incidence of follicular cell hypertrophy in thyroid and adipose infiltration of the bone marrow (indicative of morrow hyperplasia) in males treated with 500 mg/kg/day. The NOEL was considered to be 30 mg/kg/day for females and 5 mg/kg/day for males. Because the kidney changes noted in male rats were consistent with well documented changes that are peculiar to the male rat in response to treatment with some hydrocarbons, the NOAEL for males may be considered to be 30 mg/kg/day.