Cyclohexanone, 4-methoxy-

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March - Sept 2006

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 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Version / remarks:

1995

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

480-410-8

EC Name:

-

Cas Number:

13482-23-0

Molecular formula:

Hill formula: C7H12O2 CAS formula: C7H12O2

IUPAC Name:

4-methoxycyclohexan-1-one

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: aqueous 0.5% methylcellulose 400

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

28 days

Frequency of treatment:

1 per day

Doses / concentrations

Remarks:

Doses / Concentrations:
50, 300 and 1000 mg/kg bw.
Basis:
nominal in diet

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

At 1000 mg/kg/day, increased salivation was observed in all males and females on most days throughout the dosing period. At 300 and 50 mg/kg, there were no treatment-related clinical signs observed during the course of the study.

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, non-treatment-related

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

not toxicologically relevant

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Mean absolute and relative liver weights were statistically significantly greater in males and females at 1000 mg/kg/day and in males only at 300 mg/kg/day when compared to controls. These organ weight changes were considered to be attributable to treatment with the test substance.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Enlarged liver was found in all males at 1000 mg/kg/day and in 3/5 males at 300 mg/kg/day.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In the liver, minimal to moderate midzonal hepatocellular degeneration/necrosis was observed in 4/5 males at 1000 mg/kg/day and in 1/5 males at 300 mg/kg/day. This finding was associated with minimal to slight midzonal to panlobular hepatocellular hypertrophy in 4/5 males at 1000 mg/kg/day and in 2/5 males at 300 mg/kg/day. These changes were considered to be toxicologically relevant in males.
In females, up to the highest dose level tested, there was no evidence of any treatment-related histopathological change.

Effect levels

1

Key result

Dose descriptor:

NOEL

Effect level:

50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

clinical biochemistry

gross pathology

histopathology: non-neoplastic

2

Key result

Dose descriptor:

NOEL

Effect level:

300 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

clinical biochemistry

histopathology: non-neoplastic

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Mortality:

There were no mortalities observed during the course of the study.

 

Clinical signs:

At 1000 mg/kg/day, increased salivation was observed in all males and females on most days throughout the dosing period. At 300 and 50 mg/kg, there were no treatment-related clinical signs observed during the course of the study.

 

Body weight:

There was no effect on body weight or body weight gain parameters in either sex.

 

Food consumption:

Mean food consumption was unaffected by treatment in either sex.

 

Ophthalmological examination:

No ocular abnormalities were noted at ophthalmological examination.

 

Neurotoxicity assessment:

Up to the highest dose level tested of 1000 mg/kg/day, there was no evidence of a treatment-related effect on the mean exploratory locomotor activity in either sex. The slight increase in overall mean exploratory locomotor activity noted at 1000 mg/kg/day in both sexes (+23% in males and +21% in females, respectively, not statistically significant) and at 300 mg/kg/day in females (+29%, not statistically significant) were considered not to be treatment-related as the increases were of low magnitude and observed with no dose-relationship.

 

No treatment-related changes were recorded during the open field observation at any dose level in either sex. Change in gait noted in high dose males was observed in isolation and was therefore considered not to be treatment-related.

 

All reflexes and responses evaluated were unaffected by the treatment at any dose level in either sex. The changes noted in both sexes were those commonly recorded or were observed with no dose-relationship and were considered not to be treatment-related.

 

The fore- and hindlimb grip strength were unaffected by the treatment at any dose level in either sex.

 

Hematology:

No treatment-related change was noted for any of the parameters assayed in the study in either sex. The few differences observed, even if statistically significant, were considered to be incidental and/or not treatment-related.

 

Clinical Chemistry:

Increased mean total cholesterol concentrations were observed at 1000 mg/kg/day in both sexes (+42% and +35% in males and females, respectively, p<0.01) and at 300 mg/kg/day in males (+31%, p<0.05). At 1000 mg/kg/day mean triglycerides concentration was increased in females (+98%, p<0.01) and total protein and albumin concentrations were elevated in males (+13%, p<0.01).

In the absence of a dose-relation effect, the other statistically significant changes were considered not to be treatment-related.

A tendency towards decreased chloride concentrations was noted at 1000 mg/kg/day in both sexes. These changes were considered to be treatment-related but, in view of their low magnitude (-4% and -2% in males and females, respectively, p<0.01), were considered not to be toxicologically relevant. Other changes were judged to be incidental. No treatment-related change was seen at 50 mg/kg/day.

 

Urinalysis:

At 1000 mg/kg/day in males and females, mean urinary volumes were slightly greater (+65%, not statistically significant and +84%, p<0.05, respectively) and mean pH values were decreased (-23%, p<0.01 and -16%, p<0.05, respectively) when compared to controls. In males, decreased pH values were associated with a loss of the crystals usually observed in the urine of male rats.

Cellular casts were observed in all males treated at 1000 mg/kg/day, but some similar casts were also noted in one control female. However, the presence of such casts in the urine was not associated with any microscopic histopathological change. Therefore, they were considered to be treatment-related but not toxicologically relevant.

No treatment-related change was noted at 300 and 50 mg/kg/day.

 

Terminal body weight and organ weight:

There was no relevant change in mean terminal body weights when compared to controls.

 

Mean absolute and relative liver weights were statistically significantly greater in males and females at 1000 mg/kg/day and in males only at 300 mg/kg/day when compared to controls. These organ weight changes were considered to be attributable to treatment with the test substance. In males, the liver weight changes were dose-related and associated with hepatocellular hypertrophy at microscopic examination. At 1000 mg/kg/day in females, the minimally increased mean absolute liver weight and mean liver to brain weight ratio were not associated with histopathological findings.

 

All other organ weight differences were judged to be incidental in view of their individual variation.

 

Gross pathology:

Enlarged liver was found in all males at 1000 mg/kg/day and in 3/5 males at 300 mg/kg/day.

All other changes were considered as incidental and not treatment-related.

 

Microscopic pathology:

Treatment-related effects were found in the liver in males only. In the liver, minimal to moderate midzonal hepatocellular degeneration/necrosis was observed in 4/5 males at 1000 mg/kg/day and in 1/5 males at 300 mg/kg/day. This finding was associated with minimal to slight midzonal to panlobular hepatocellular hypertrophy in 4/5 males at 1000 mg/kg/day and in 2/5 males at 300 mg/kg/day. These changes were considered to be toxicologically relevant in males. In females, up to the highest dose level tested, there was no evidence of any treatment-related histopathological change.

 

The other microscopic findings, including the higher incidence of necrotic foci in the liver, were those commonly observed in the rat of this strain and age and were considered to be incidental in origin.

Applicant's summary and conclusion

Conclusions:

Although for the liver findings especially in male rats STOT-RE was considered when applying Haber's rule on equivalent guidance values, based on WoE no classification for STOT-RE is proposed with the following arguments:


1) low severity (minimal) of histopathological findings in the liver of male rats at 300 mg/kg in combination with no findings on liver-specific enzyme parameters in the blood

2) histopathological findings on hypertrophy are regarded as potentially reversible

3) histopathological findings on necrosis are minimal and focal

4) liver enlargement is often observed as an adaptive mechanism due to rat-specific CYP induction

5) increased levels of cholesterol and triglycerides were not dose-dependent

Executive summary:

In conclusion the No Observed (Adverse) Effect Level of the test substance in this study was 50 mg/kg/day in males and 300 mg/kg/day in females over a 28-day administration period by gavage.