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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Reliable study summary (NTP), however, no full OECD compliant chronic study (no haematology and clinical biochemistry).

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1990
Report Date:
1990

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Fischer 344/N rats and B6C3F1 mice were used in this study. Groups of 50 rats of each sex and groups of 50 male mice were administered 0, 200, or 400 mg/kg the test substance in corn oil by gavage, 5 days per week for 103 (rats) or 104 (male mice) weeks. Groups of 50 female mice were administered 0, 300, or 600 mg/kg, 5 days per week for 103 weeks.
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Batch No.: JE5718HE, purity: >99%
Batch No.: 005-0120, purity: approximately 99%

Test animals

Species:
other: rat and mouse
Strain:
other: Fischer 344/N rats and B6C3F1 mice
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Frederick Cancer Research Facility
- Age at study initiation: Rats: 8 wk; Mice: male: 8 wk, female: 9 wk
- Housing: five per cage, Polycarbonate cages with reemay spun-bonded polyester filters
- Diet (e.g. ad libitum): NIH 07 Rat and Mouse Ration; available ad libitum
- Water (e.g. ad libitum): available ad libitum
- Acclimation period: Rats: 20 d; Mice: 19 d

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16.7-31.7
- Humidity (%): 25%-86%
- Air changes (per hr): 15 room air changes/h
- Photoperiod (hrs dark / hrs light): fluorescent light 12 h/d

IN-LIFE DATES:
Rats: From: 18 January 1982 To: 20 January 1984;
Male mice: From: 19 January 1982 To: 26 January 1984;
Female mice: From: 2 March 1982 To: 1 March 1984

No additional data

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
VEHICLE
- Amount of vehicle (if gavage): rats: 5 mL/kg; mice: 10 mL/kg

No additional data
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The test substance in corn oil was found to be stable at room temperature in the dark for 14 days when stored in sealed vials. A small (5%) loss occurred when the test substance in corn oil was exposed to air and light for 3 hours at room temperature under simulated dosing conditions. Dose formulations were prepared once a week and were stored in the dark at room temperature under nitrogen for a maximum of 14 days.
Duration of treatment / exposure:
103 weeks for rats and female mice, 104 weeks for male mice
Frequency of treatment:
5 days per week
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 200 or 400 mg/kg for rats and male mice; 0, 300 or 600 mg/kg for female mice
Basis:
actual ingested
No. of animals per sex per dose:
50 males and 50 females of each species per dose
Control animals:
yes, concurrent vehicle
Details on study design:
None stated
- Dose selection rationale: Rats: Because of the various lesions observed at 800 mg/kg but not at 400 mg/kg, doses selected for rats for the 2-year studies were 200 and 400 mg/kg the test substance, administered in corn oil by gavage, 5 days per week.
Mice: Doses of the test substance selected for male mice for the 2-year studies were 200 and 400 mg/kg, based on renal lesions in one male mouse given 600 mg/kg and in all of the male mice given 1200 mg/kg for 13 weeks. Doses selected for female mice for the 2-year studies were 300 and 600 mg/kg because of the steep dose-response curve for mortality demonstrated in the 16-day and 13-week studies (survival-16-day study: 1600 mg/kg, 0/5; 13-week study: 1200 mg/kg, 9/10).

No additional data
Positive control:
No stated

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice per day

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice per day

BODY WEIGHT: Yes
- Time schedule for examinations: on day 1, once a week for 13 weeks and once a month thereafter

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

No additional data
Sacrifice and pathology:
GROSS PATHOLOGY: yes. Number of animals receiving complete necropsy examination; all gross lesions including masses examined microscopically.
HISTOPATHOLOGY: Yes. The following tissues examined histologically for all vehicle control and high dose animals, low dose male rats, and all animals dying before the end of the studies: adrenal glands, brain, cecum, colon, duodenum, epididymis/prostate/testes or ovaries/uterus, esophagus, eyes (rats), femur including marrow, gallbladder (mice), gross lesions and tissue masses, heart, ileum, jejunum, kidneys, liver, lungs and mainstem bronchi, mammary gland, mandibular or mesenteric lymph nodes, nasal cavity and turbinates, pancreas, parathyroid glands, pituitary gland, preputial or clitoral gland (rats), rectum, salivary glands, sciatic nerve, skin, spinal cord (rats), spleen, stomach, thymus, thyroid gland, trachea, and urinary bladder. Tissues examined for low dose groups include adrenal glands, bone, brain, clitoral gland, eyes, gross lesions, heart, kidneys, liver, lungs, pituitary gland, spinal cord, spleen, and stomach for female rats and gross lesions and stomach for mice.
Other examinations:
None stated
Statistics:
Survival analyses: The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958) and is presented in the form of graphs. Statistical analyses for a possible dose-related effect on survival used the method of Cox (1972) for testing two groups for equality and Tarone's (1975) life table test for a dose-related trend. When significant survival differences were detected, additional analyses using these procedures were carried out to determine the time point at which significant differences in the survival curves were first detected. All reported P values for the survival analysis are two-sided.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food efficiency:
not specified
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
Rats: The survival of the high dose group of male rats was significantly lower than that of the vehicle controls after day 373; no other significant differences were observed between any groups of either sex.
Mice: No significant differences were observed between any groups of either sex in mortality. No compound-related clinical signs were observed in clnical signs.

BODY WEIGHT AND WEIGHT GAIN
Rats: Mean body weights of dosed and vehicle control rats were similar throughout the studies.
Mice: Mean body weights of dosed and vehicle control mice were similar throughout the studies. No compound-related clinical signs were observed.

GROSS PATHOLOGY (Neoplastic effects)
Rats
Pancreas: Hyperplasia and adenomas of the exocrine pancreas were marginally increased in high dose male rats; the incidence of adenomas in the high dose group was significantly greater than that in the vehicle controls. The incidence of adenomas in the high dose group, however, was well within the range of historical corn oil vehicle control incidences of pancreatic acinar cell neoplasms at the study laboratory (0/49-11/50, 22%) and only slightly greater than the mean historical control incidence at the study laboratory (36/397, 9%).
Mesothelium: Malignant mesotheliomas of the tunica vaginalis and/or peritoneum (mesentery) were marginally increased in dosed male rats. The incidence of 5/50 in the low dose group slightly exceeded the highest incidence observed in a corn oil vehicle control group (4/50, 8%) at the study laboratory. Because there was no significant increase in the high dose group and because the incidence in the low dose group was only marginally increased relative to the mean historical corn oil vehicle control incidence at the study laboratory (15/450, 3%), the malignant mesotheliomas were considered to be unrelated to the administration of the test substance.
Hematopoietic System: Mononuclear cell leukemia in male rats occurred with a significant positive trend; the incidences in the dosed groups were significantly greater than that in the vehicle controls.
Forestomach: Squamous papillomas were seen in two high dose female rats; the historical incidence of forestomach neoplasms in corn oil vehicle control female F344/N rats is 9/2,085 (0.4%), and the highest observed incidence is 2/49. Hyperplasia of the mucosa was seen in 5/50 vehicle control, 2/50 low dose, and 3/50 high dose female rats.

Mice: Forestomach: Focal hyperplasia and squamous cell papillomas were increased in dosed male and female mice; the incidences of squamous cell papillomas in low and high dose female mice were significantly greater than that in vehicle controls.
Focal hyperplasia of the forestomach was characterized by a localized region of increased thickness of the stratified squamous epithelium. In the less severe lesions the surface of the epithelium was irregular or slightly folded, whereas in the more advanced lesions the epithelium was more extensively folded, producing short papillary projections with a narrow core of connective tissue. The squamous cell papillomas exhibited greater complexity of the papillae and the formation of a stalk .
A squamous cell carcinoma was diagnosed in a single high dose female mouse by the pathologist at the study laboratory.

HISTOPATHOLOGY: NON-NEOPLASTIC
Incidences of lesions were not related to the test substance or showed a dose response relationship in rats
In mice the incidence of forestomach hyperplasia was increased at 200 and 400 mg/kg bw

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
The only effects of the test substance were those seen in the forestomach of mice. The incidences of uncommonly occurring squamous cell papillomas of the forestomach in both exposure groups were significantly greater than those in vehicle controls (male: vehicle control, 1/50; low dose, 2/50; high dose, 5/50; female: 0/50; 5/50; 6/50). The increased incidences of papillomas were accompanied by dose-related increases in the incidences in forestomach hyperplasia (male: 7/50; 8/50; 16/50; female: 12/50; 23/50; 39/50).

No additional data

Effect levels

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Dose descriptor:
NOAEL
Effect level:
400 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Rat; no effects observed
Dose descriptor:
LOAEL
Effect level:
300 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Mouse: forestomach hyperplasia
Dose descriptor:
NOAEL
Effect level:
< 300 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Mouse

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity or other effects as investigated in this study of the test substance for male or female F344/N rats receiving 200 or 400 mg/kg per day. There was some evidence of carcinogenic activity of the test substance for male or female B6C3F1 mice, as indicated by increased incidences of squamous cell papillomas and hyperplasia of the forestomach at both doses tested. Female rats and male and female mice might have been able to tolerate higher doses.
Executive summary:

Fischer 344/N rats and B6C3F1 mice were used in this study.Groups of 50 rats of each sex and groups of 50 male mice were administered 0, 200, or 400 mg/kg the test substance in corn oil by gavage, 5 days per week for 103 (rats) or 104 (male mice) weeks. Groups of 50 female mice were administered 0, 300, or 600 mg/kg, 5 days per week for 103 weeks.

 

Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity or other effects as investigated in this study of the test substance for male or female F344/N rats receiving 200 or 400 mg/kg per day. There was some evidence of carcinogenic activity of the test substance for male or female B6C3F1 mice, as indicated by increased incidences of squamous cell papillomas and hyperplasia of the forestomach at both doses tested. Female rats and male and female mice might have been able to tolerate higher doses.