Registration Dossier

Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well conducted study, carried out by Research Institute for Animal Science in Biochemistry and Toxicology (Japan)

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1999

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Principles of method if other than guideline:
TC-Freetext:
*Age at study initiation: 8 week old for both sexes
*Mean weight at study initiation Dose levels(mg/kg) 0 2.5 12.5 60 Body weight (g±SD) Male 291.5±9.0 291.6±9.0 291.7±8.7 291.8±8.1 Female 220.1±7.0 220.1±7.5 219.9±6.7 220.2±7.2 No. of animals per sex per dose: 13 per sex per dose group
*Study Design
-Terminal killing: Males; day 43, Females; day 4 of lactation
-Clinical observations performed and frequency: General condition was observed once a day. Body weight and food consumption were determined once a week. Food consumption in mating period was not. Hematological and serum biochemical examinations, and urinary test were performed for all males.
-Organs examined at necropsy: Organ weight: brain, heart, liver, kidneys, spleen, thymus, adrenal glands, testes, epididymides Microscopic: control & all treated groups/ liver, spleen(female only),adrenal glands(female only), control & 60 mg/kg groups/brain, heart, kidneys,spleen, thymus, adrenal glands, testes, epididymides.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Produced by Sumitomo Chemical, Lot No.1271012. Purity 99.23%

Test animals

Species:
rat
Strain:
Crj: CD(SD)
Sex:
male/female

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Duration of treatment / exposure:
male: 42 days,
female: from 14 days before mating to day 3 of lactation
Frequency of treatment:
7 days/week
Doses / concentrations
Remarks:
Doses / Concentrations:
2.5, 12.5, 60 mg/kg/day (in corn oil)
Basis:

No. of animals per sex per dose:
13 per sex per dose group
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: no
Positive control:
no data

Examinations

Observations and examinations performed and frequency:
-Clinical observations performed and frequency: General condition was observed once a day. Body weight and food consumption were determined once a week. Food consumption in mating period was not. Hematological and serum biochemical examinations, and urinary test were performed for all males.
Sacrifice and pathology:
-Terminal killing: Males; day 43, Females; day 4 of lactation
-Organs examined at necropsy: Organ weight: brain, heart, liver, kidneys, spleen, thymus, adrenal glands, testes, epididymides Microscopic: control & all treated groups/ liver, spleen(female only), adrenal glands(female only), control & 60 mg/kg groups/brain, heart, kidneys,spleen, thymus, adrenal glands, testes, epididymides.
Other examinations:
reproductive and developmental toxicity parameters were also examined, for detail see 7.8 (toxicity to reproduction)
Statistics:
no data

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 consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not specified
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
12.5 mg/kg bw/day (nominal)
Sex:
male/female
Dose descriptor:
LOAEL
Effect level:
60 mg/kg bw/day (nominal)
Sex:
male/female

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

RS-Freetext:
*LOAEL= 60 mg/kg/day, NOEL = 12.5 mg/kg/day
males : histopathological changes in liver
females: suppression of body weight gain and histopathological changes in liver
* Body weight: Suppression of body weight gain was observed at day 14 of pregnancy and day 4 of lactation in the 60 mg/kg female.
Body weight in female

Dose level(mg/kg/day) 0 2.5 12.5 60
Body weight (g, mean±SD)
day 14 of pregnancy 338.7±15.1 343.8±13.5 335.7±26.7 310.1±24.9**
Day 4 of lactation 327.4±20.9 336.5±19.9 311.8±23.9 280.1±29.8**
(**P< 0.01)
*Food consumption: Decrease in food consumption was observed lactation period in the female group at 60 mg/kg.(Statistical significant was P< 0.01 on the day 4 of
lactat ion)
*Clinical signs (description, severity, time of onset and duration): No significant effect was observed.
in the female group at 60 mg/kg.(Statistical significant was P< 0.01 on the day 4 of lactation)
*Clinical signs (description, severity, time of onset and duration): No significant effect was observed.
*Mortality and time to death: The death was not observed in any group.
*Hematology and biochemical findings: No significant effect was observed.
*Gross pathology incidence and severity: No significant effect was observed.
*Organ weight changes :
Male: Increase in absolute kidneys weight was observed in the 60 mg/kg group (P<0.05).
Female: Decrease in absolute heart and spleen weights , and increase in relative brain,liver and kidneys weights were observed in the 60 mg/kg group (P< 0.01).
*Histopathology (incidence and severity)
Male & female: Hypertrophy of centrilobular hepatocytes with eosinophilic was observed at 60 mg/kg group. Histopathological change considered to be significant
biologically was not observed in other organs.

Histopathological changes in the liver

Sex Male Female

Dose level( mg/kg/day)
0 2.5 12.5 60 0 2.5 12.5 60 Hypertrophy,eosinophilic
Hepatocyte,centrilobular
0/13 0/13 0/13 5/13* 0/13 0/13 0/13 10/13** Necrosis
2/13 1/13 1/13 1/13 4/13 2/13 1/13 6/13 Fibrosis,focal
1/13 0/13 1/13 0/13 0/13 0/13 1/13 1/13 Fatty hange,periportal
13/13 13/13 13/13 13/13 3/13 1/13 2/13 7/13
( * P< 0.05 , ** P< 0.01)
Necrosis, Fibrosis and fatty change in peripotal region are thought to be spontaneous lesion on the liver of male and female rats. Historical control incidence of fifteen Combined Repeated Dose and Reproductive/Developmental
Toxicity Studies performed at the same laboratory was checked out. The range of Necrosis, Fibrosis and Fatty change in periportal region were 0-31%, 0-23% and 0-
100%, respectively. Especially, the historical incidence of Fatty change, periportal was 100% in all of 15 studies investigated in male rats in the laboratory. In the
study of 6-tert-butyl-m-cresol, the incidence of Necrosis, focal (15% in male, 23% in female), Fibrosis, focal (8% in male, 0% in female), Fatty change, periportal (100% in male, 23% in female) in control animals falls within historical control range. Therefore, these lesions in the male and female liver of 6-tert-butyl-mcresol study were considered to be spontaneous and animals used in the study were normal.

Applicant's summary and conclusion

Conclusions:
Toxic effects in this study are suppression of body weight gain and increase of relative liver weight in the 60 mg/kg female, and histopathologica changes of the liver in the 60 mg/kg male and female. The NOEL is considered to be 12.5 mg/kg/day for both sexes.
Executive summary:

method: combined repeat dose reproductive/developmental toxicity screening study according OECD TG 422

result: NOEL = 12.5 mg/kg/day (rat, male + female), LOAEL = 60 mg/kg/day (rat, male + female); Toxic effects in this study are suppression of body weight gain and increase of relative liver weight in the 60 mg/kg female, and histopathologica changes of the liver in the 60 mg/kg male and female.

reference: MHW, Japan (1999)