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Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From April 2, 2002 to July 31, 2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other:
Remarks:
OECD 407 guideline study in compliance with GLP. γ-Caprolactone, as a linear saturated 4-hydroxycarboxylic acid derived-lactones, is considered adequate for read-across purpose (see §"Toxicokinetics").

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2003
Report Date:
2003

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity in Rodents)
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Limit test:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Details on test material:
- Name of test material (as cited in study report): gamma-CL
- Physical state: clear colourless liquid
- Storage condition of test material: room temperature protected from light

Test animals

Species:
rat
Strain:
other: Crl:CD®(SD)IGS BR
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS:
- Source: Charles River Laboratories, Inc., Raleigh, North Caroline
- Age at study initiation: 34 days old at receipt, approximately seven weeks old at study initiation
- Weight at study initiation: males: 214-265 g; females: 157-200 g
- Housing: individually, in clean, wire-mesh cages suspended above cage-board
- Diet (e.g. ad libitum): ad libitum except during the period of fasting prior to blood collection, PMI Nutrition International, Inc. Certified Rodent LabDiet® 5002 (analysis certified)
- Water (e.g. ad libitum): ad libitum, reverse-osmosis-treated (on-site) municipal water (analysis certified)
- Acclimation period: 17 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.7 ± 3
- Humidity (%): 50 ± 20
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From April 2, 2002 To: May 31, 2002 (recovery necropsy)

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Remarks:
deionized
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: The 1000 mg/kg bw/d test article formulation was a weight/volume (test article/vehicle) mixture. For this group, the appropriate amount of the test article was weighted into a tared weighting vessel. Approximately 60 % of the vehicle was added to a calibrated storage container, and a deep vortex was created with a magnetic stir bar. The test article was slowly transferred quantitatively into the rapidly stirring vehicle and stirred until dissolved (approximately one minute). The remaining amount of vehicle was added to bring the volume to the calibration mark. The formulation was stirred until uniform and throughout use, using a magnetic stirrer. The mixture was used as a stock formulation to prepare the 30, 100 and 300mg/kg bw/d group dosing formulations. For these groups, the appropriate volume of the stock formulation was added to achieve the total volume for each group. The dosing formulations were stored refrigerated, protected from light. The test article formulations were prepared approximately weekly, then separated into aliquots for daily dispensation. All test article formulations were stirred continuously throughout the preparation, sampling and dose administration procedures.

VEHICLE
- Justification for use and choice of vehicle (if other than water): NA
- Amount of vehicle (if gavage): 10 mL/kg bw
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Prior to the initiation of dose administration, samples (10 mL each) for homogeneity determination were collected from the top, middle and bottom strata of the all dosing formulations, including the control group. In addition, duplicate samples (10 mL each) for stability determinations were collected from the top and bottom strata of these same dosing suspensions; one set was stored refrigerated for 10 days and one set was stored at room temperature for 10 days. Both sets were protected from light. Samples (10 mL each) for concentration analysis were collected from the first, second and third weekly preparations from each dosing formulation (including the control group.
All analyses were conducted by the Analytical Chemistry Department, WIL Research Laboratories, Inc. The test article formulations were found to be homogenous (the RSD for the overall mean concentration was ≤ 10 % at a concentration that is within the acceptable limits), contain the amount of test article specified in the protocol (analyzed concentrations were within ± 10 % of the target dose concentrations) and stable for at least 10 days when stored refrigerated or at room temperature (the mean concentrations were no less that 90 % of the time zero concentrations).
Duration of treatment / exposure:
28 days
Frequency of treatment:
Once daily
Doses / concentrationsopen allclose all
Dose / conc.:
30 mg/kg bw/day (actual dose received)
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
300 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
5 animals/sex/dose, 5 additional recovery animals in control and high-dose group
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: not detailed in the study report
- Rationale for animal assignment (if not random): computerized randomization procedure
- Rationale for selecting satellite groups: control and high dose groups
- Post-exposure recovery period in satellite groups: 14 days
Positive control:
Not applicable

Examinations

Observations and examinations performed and frequency:
MORTALITY and MORIBUNDITY: Yes
- Time schedule: twice daily, once in the morning and once in the afternoon

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily, prior to dose administration and approximately one to two hours following dose administration. Once daily during the recovery period.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly, beginning the week prior to test article administration and prior to scheduled necropsies

BODY WEIGHT: Yes
- Time schedule for examinations: at least weekly, beginning two weeks prior to test article administration. Mean body weights and mean body weight changes were calculated for the corresponding intervals. Final body weights (fasted) were recorded prior to each scheduled necropsy.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): NOT A FEEDING STUDY, however individual food consumption was recorded weekly, beginning two weeks prior to test article administration. Food intake was calculated as g/animal/day for the corresponding body weight intervals.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): NOT A DRINKING WATER STUDY

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to initiation of dose administration and near the end of the treatment period
- Dose groups that were examined: all animals
- All ocular examinations were conducted using an indirect ophthalmoscope and slit lamp biomicroscope, preceded by papillary dilation with 0.5 % mydriacyl.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the scheduled necropsies (study week 4 and 6).
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes, overnight
- How many animals: all surviving animals, and all recovery groups animals
- Parameters checked in table 7.5.1/2 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the scheduled necropsies (study week 4 and 6).
- Animals fasted: Yes, overnight
- How many animals: all surviving animals and all recovery groups animals
- Parameters checked in table 7.5.1/2 were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: at the scheduled necropsies (study week 4 and 6).
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No
- Parameters checked in table 7.5.1/2 were examined.

NEUROBEHAVIOURAL EXAMINATION: Yes
Functional observation battery (FOB)
- Dose groups and time schedule for examinations: Five animals/sex/group prior to the initiation of dose administration and during study week 3, and for five animals in the control and 1000 mg/kg bw/d groups during study week 5 (recovery period).
Sound-attenuated room equipped with a white noise generator set top operate at 70 ± 10 db with one exception; home cage observations were performed in the animal room.
- Parameters examined: see Table 7.5.1/3

Locomotor activity
- Dose groups and time schedule for examinations: Five animals/sex/group prior to the initiation of dose administration and during study week 3, and for five animals in the control and 1000 mg/kg bw/d groups during study week 5 (recovery period).
- Measured automatically using the San Diego Instrument, Inc. Photobeam Activity System (San Diego Instruments, Inc. San Diego, California). This personal computer-controlled system utilizes a series of infrared photobeams surrounding a clear plastic, rectangular cage t quantify each animal’s motor activity. The testing of treatment groups was done accordingly to replicate sequence. Each animal was tested separately. Data were collected in five-minute epochs (print intervals) and the test session duration was 60 minutes.
Data for ambulatory and total motor activity were tabulated. Total motor activity was defined as a combination of fine motor skills (i.e., grooming, interruption of one photobeam) and ambulatory motor activity (interruption of two or more consecutive photobeams).
Sacrifice and pathology:
GROSS PATHOLOGY: Yes (See table 7.5.1/4). Animals were anesthetized by isoflurane and exsanguinated.
HISTOPATHOLOGY: Yes (See table 7.5.1/4)
Other examinations:
ULTRASTRUCTURAL EVALUATION: liver specimens collected in McDowell-Trump fixative for electron microscopy were embedded at North Carolina State University. Samples for the primary necropsy were subjected to ultrastructural examination at EPL, Durham, North Caroline.
Statistics:
All statistical tests were performed using appropriate computing devices or programs. Analyses were conducted using two-tailed tests (except as noted otherwise) for minimum significance levels of 1 % and 5 %, comparing each test article-treated group to the control group by sex. Each mean was presented with the standard deviation (S.D.) and the number of animals (N) used to calculate the mean. Statistical analyses were not conducted if the number of animal was two or less. Due to the different rounding conventions inherent in the types of software used, the means and standard deviations on the summary and individual tables may differ by ± 1 in the last significant figure.
Body weight, body weight change, food consumption, continuous FOB, Locomotor Activity Data, clinical pathology and organ weight data were subjected to a parametric one-way analysis of variance (ANOVA) to determine intergroup differences. If the ANOVA revealed statistical significance (p < 0.05), Dunnett’s test was used to compare the test article-treated groups to the control group. FOB parameters that yielded scalar or descriptive data were analyzed using Fisher’s Exact Test. Clinical pathology values for white blood cell types that occur at a low incidence (i.e. monocytes, eosinophils and basophils) were not subjected to statistical analysis.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
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:
effects observed, treatment-related
Description (incidence and severity):
lower cholesterol levels in the 1000 mg/kg bw/d group, recovery occured
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
increased liver weight at 1000 mg/kg bw, recovery occured
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Pale liver in 2/5 M and 4/5 F dosed with 1000 mg/kg bw/d, correlated with increased lipid droplets
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
All animals survived to the scheduled necropsy.
Test article-related clinical findings consisted of clear, yellow or red material around the mouth and/or the urogenital area or forelimbs observed at the 1000 mg/kg bw/d group at low incidence at the time of dosing (females) and one hour following dosing (males and females).
In addition, hypereactivity was noted infrequently in 30, 100 and 300 mg/kg bw/d group females and in single occurrences in the 1000 mg/kg bw/d group males and females. However, since the occurrences were infrequent and no dose and/or temporal relationship was apparent, these findings were not considered to be test article-related. Other clinical findings were not observed in a dose-related manner, occurred in singles animals and/or are common findings in laboratory rats of this age and strain.

BODY WEIGHT AND WEIGHT GAIN
No test article-related trends in body weights or body weight gains were noted at any dose level. The only statistically significant (p < 0.05 or p < 0.01) differences from the control group values were increases in the 100 mg/kg bw/d group females (study weeks 0-1 through 0-3) and the 300 mg/kg bw/d females (study week 0-3). No dose-relationship was evident.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
No test article related-effects on food consumption were observed at any dose level.

OPHTHALMOSCOPIC EXAMINATION
There were no test article-related ophthalmic findings.

HAEMATOLOGY
There were no test article-related changes in hematology. The only statistically significant (p < 0.05) difference from the control group was a slightly lower mean MCHC value in the 1000 mg/kg bw/d group females at the week 6 recovery evaluation. This difference from the control group was not attributed to the test article since a similar decrease was not observed in these females at the study week 4 evaluation or in the 1000 mg/kg bw/d group males at either evaluation.

CLINICAL CHEMISTRY
Test article-related lower cholesterol levels were noted in the 1000 mg/kg bw/d group males and females at the study week 4 evaluation. Some of the differences were statistically significant (p < 0.05 or p < 0.01).
Mean cholesterol levels in the 1000 mg/kg bw/d group males and females were lower (statistically significant at p < 0.05 or p < 0.01) than those in the control group. At the recovery evaluation (study week 6), the mean cholesterol levels in the 1000 mg/kg bw/d group males and females were similar to those in the control. Another possible treatment-related effect in the 1000 mg/kg bw/d group females was slightly lower mean sodium levels at study week 4. The difference from the control group was statistically significant (p < 0.05). However, the biological significance of the lower sodium level is unclear since the magnitude of the change from the control value was small.
Other statistically significant changes in mean serum chemistry values at study week 4 were also observed, but the lack of dose-related trends or similar findings for comparable dosed rats of the opposite sex suggests that these findings are more likely random occurrences that treatment-related effects. These changes included higher mean albumin, total protein, urea nitrogen and calcium levels in the 1000 mg/kg bw/d group females, higher mean asparatate aminotransferase levels in the 1000 mg/kg bw/d group males and lower mean chloride levels in the 100 and 300 mg/kg bw/d group males.

URINALYSIS
There were no test article-related changes in urinalysis parameters. The only statistically significant (p < 0.05) difference from the control group was a slight increase in specific gravity in the 1000 mg/kg bw/d group females at the week 6 recovery evaluation. This difference was not observed in these females at the study week 4 evaluation or in the 1000 mg/kg bw/d group males at either evaluation.

NEUROBEHAVIOUR
- FOB:
No remarkable differences on home cage observations, handling observations, open field observations, sensory observations, neuromuscular observations were apparent between the control and test article-related groups during study weeks 3 and 5.
No test article-related physiological observations were noted. Statistically significant (p < 0.05 or p < 0.01) increases were observed in body weight for the 100 mg/kg bw/d group females during pretest and catalepsy for the 30 mg/kg bw/d group males at study week 3. Since these findings occurred during the pretest period or were not observed in a dose-related manner, they were not attributed to the test article. In addition, a statistically significant (p < 0.05) decrease in body temperature was observed in the 1000 mg/kg bw/d group females at the week 5 recovery. Since this finding occurred during the recovery period, the differences were not attributed to the test article.
- Locomotor activity:
There were no test article-related effects on motor activity.

ORGAN WEIGHTS
Test article-related increased in liver weights (absolute and relative to final body/brain weights) were observed in the 1000 mg/kg bw/d group females at the study week 4 primary necropsy. A slight increase in liver weight relative to final body weight in the 1000 mg/kg bw/d group males at study week 4 was considered equivocal. At the study week 6 recovery necropsy, liver weights in the 1000 mg/kg bw/d group males and females were comparable to the control.
Mean absolute and relative (to final body and to brain weight) liver weights in the 1000 mg/kg bw/d group females were increased 27-31 % compared to the control group at the primary necropsy (study week 4). The differences were statistically significant (p < 0.01). Mean relative (to final body weight) liver weight in the 1000 mg/kg bw/d group males was also increased by 13 % (p < 0.05) compared to the control group. Mean absolute and relative liver weight in the 1000 mg/kg bw/d group males and females were similar to those in the control group at the study week 6 recovery necropsy. No other test article-related changes in organ weights were noted at the study week 4 primary necropsy, and no test article-related effects on organ weights were observed at the study week 6 recovery necropsy.
Statistically significant increases (p < 0.01) were observed in mean absolute brain weights in the 100 and 300 mg/kg bw.d group females compared to the control. No dose-relationship was evident; therefore, these increases were considered incidental.

GROSS PATHOLOGY
Test-article findings were observed in the liver in the 1000 mg/kg bw/d group males and females.
At the primary necropsy, a pale liver was observed in two males and four females in the 1000 mg/kg bw/d group. These findings correlated with the increased lipid droplets observed by election microscopy. No other test article-related findings were observed at the primary necropsy, and no test article-related changes were observed at the recovery necropsy.

HISTOPATHOLOGY:
There were no histopathologic observations that were conclusively test article-related.
A very slight increased incidence of foamy cytoplasm of hepatocytes (termed “vacuolation, cytoplasm”) was observed in the livers of two females and one male in the 1000 mg/kg bw/d group relative to the control group.

ULTRASTRUCTURAL EVALUATION:
Representative liver sections were examined for three males and three females form the control and 1000 mg/kg bw/d groups collected at the primary necropsy.
The livers from the 1000 mg/kg bw/d group males had considerably higher numbers of lipid bodies in the hepatocytes. The numbers of lysosomes and dark glycogen granules were also slightly increased. The ultrastructural features of the livers from the 1000 mg/kg bw/d group females were characterized by test article-related lipid content to the extent seen in the 1000 mg/kg bw/d group males. The distribution and severity of increased glycogen granules were also comparable to that observed in these males.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Effects noted at 1000 mg/kg bw/d were very minimal and not indicative of toxicity
Dose descriptor:
NOEL
Effect level:
300 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: no effects at 300 mg/kg bw/day

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

none

Applicant's summary and conclusion

Conclusions:
Under the test conditions, the NOEL was considered to be 300 mg/kg bw/day and the NOAEL to be 1000 mg/kg bw/d. γ-Caprolactone is not classified for damage to organs through prolonged oral dose repeated exposure according to the criteria of the Annex I of the Regulation (EC) No 1272/2008 (CLP) and the GHS.
Executive summary:

In a sub-acute toxicity study performed according to the OECD test guideline No. 407 and in compliance with GLP, γ-Caprolactone diluted in deionized water was administered by gavage to Crl:CD®(SD)IGS BR rats (5/sex/group) at 30, 100, 300 or 1000 mg/kg bw/day for 28 days A control group received vehicle alone at the same volume-dosage (10 mL/kg bw/day). Control and high dose group contained an additional 5 rats/sex/group for evaluation of recovery from the test article-related effects, following a 14-day recovery period.

For toxicology assessment, all animals were observed twice daily for mortality and moribundity. Clinical examinations were performed daily and detailed physical examinations were performed weekly. Individual body weights and food consumption were recorded weekly. Functional observation battery (FOB) and locomotor activity data were recorded for five animals/sex/group prior to the initiation of dose administration and during study week 3, and for the recovery animals during week 5. Clinical pathology evaluations were performed on all animals. Ophthalmic examinations were performed during weeks -2 and 3. Complete necropsies were conducted on all animals, and selected organs were weighted at the scheduled necropsies. Selected tissues were examined microscopically for all animals. Sections of the livers from six rats/sex/group were collected at the scheduled necropsies for possible ultrastructural evaluation. Samples collected at the primary necropsy were examined by electron microscopy.

 

All animals survived to the scheduled necropsies. Body weights, food consumption, hematology and urinalysis parameters were unaffected by test article administration. There were no test article-effects on FOB parameters or locomotor activity. No test article-related ophthalmic findings were noted. No test article-related changes were noted in the 30, 100 or 300 mg/kg bw/d groups.

Test article-related effects noted in the 1000 mg/kg bw/d group consisted of:

- Slightly increased incidence of wet and/or dried material (clear, red and/or yellow) around the mouth and/or the urogenital area of forelimbobserved at the 1000 mg/kg bw/d group at low incidence at the time of dosing (females) and one hour following dosing (males and females). These findings were not considered to be adverse.

- Lower mean cholesterol levels (males and females). This finding was not considered to be adverse.

- Increased mean liver weights (absolute and/or relative to final body and/or brain weights) were noted for both males and females at the primary (week 4) necropsy. This increase was not observed at the recovery period.

- Pale liver was noted in two males and four females at the primary necropsy and correlated with the increased lipid bodies seen by election microscopy.

- No conclusive test article-related light microscopic findings were noted. However, a very slight increase in the incidence of cytoplasmic vacuolation was observed in one male and two females in the 1000 mg/kg bw/d group. This observation may explain the increased liver weights and ultrastructural findings.

- Marked increase in lipid bodies and a slight increase in dark glycogen granules within the hepatocytes of those livers examined by electron microscopy. The increased lipid bodies may account for the increased liver weights and the gross observations of pale liver, particularly in females.

 

Based on the results of this study, the NOEL was 300 mg/kg bw/day and the NOAEL was 1000 mg/kg bw/d. The effects noted at the 1000 mg/kg bw/d were very minimal and not indicative of significant toxicity. There was no evidence of liver toxicity. The higher liver weights, the slightly higher incidence of hepatic cytoplasmic vacuolation observed by light microscopy in the females and the higher incidence of lipid bodies and dark glycogen granules observed by electron microscopy were most likely a physiological adaptation to the administration of the test article. Consequently, they were not considered as adverse. Furthermore, the changes were reversible as they were no longer observed following the 14-day recovery period.

 

Therefore, γ-Caprolactone is not classified for damage to organs through prolonged oral dose repeated exposure according to the Regulation (EC) No 1272/2008 (CLP) and the GHS.

This study is considered as acceptable and satisfies the requirement for repeated dose toxicty endpoint.