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Toxicological information

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
Study period:
From October 1979 to January 1980
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1980
Report date:
1980

Materials and methods

Principles of method if other than guideline:
Male and female Fisher rats (15/sex/group) received the substance by oral gavage at dose levels of 0, 50, 100, 300, 700 and 1500 mg/kg bw, in olive oil. One group of 15/sex served as the control and received only the vehicle, in volumes comparable to those received by treated groups. Animals were observed daily, body weight and food consumption was measured weekly. Clinical pathology investigations (haematology, clinical chemistry and urinalysis) were conducted prior to termination in Week 13. All animals were subject to a full necropsy and histopathological examination of a comprehensive range of tissues.
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
4-methylstyrene
EC Number:
210-762-8
EC Name:
4-methylstyrene
Cas Number:
622-97-9
Molecular formula:
C9H10
IUPAC Name:
1-methyl-4-vinylbenzene
Test material form:
liquid
Details on test material:
- Batch/lot No.: 10037901

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals or test system and environmental conditions:
F344 Fisher rats were obtained from Charles River Breeding Laboratories, Wilmington, MA. Age at initiation was approx. 6 weeks. Initial body weights were: males 109.0 – 156.8 g and females 81.1 – 124.2 g. Housed singly and commercial rodent ration (Purina Laboratory Chow) and tap water (automated system) freely available.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
olive oil
Details on oral exposure:
All animals received 1 mL/kg olive oil. These solutions were made weekly. Dose volumes were then adjusted to take account of test substance. Those dose volumes (mL/kg) were 1.0, 1.06, 1.12, 1.34, 1.79 and 2.69 and were adjusted according to the most recently recorded mean body weight for each group/sex.
Analytical verification of doses or concentrations:
no
Duration of treatment / exposure:
Daily
Frequency of treatment:
13 weeks
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Dose / conc.:
50 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.:
700 mg/kg bw/day (actual dose received)
Dose / conc.:
1 500 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
15 males and 15 females
Control animals:
yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:
Mortality: twice daily
Clinical signs: weekly
Body weight: weekly
Food consumption: weekly

Clinical pathology: at termination
Blood samples form the orbital sinus, urine samples overnight in metabolism cages.
Haematology samples were examined for haematocrit, haemoglobin, erythrocyte, platelet count and leukocyte count and differentials.

Clinical chemistry samples were examined for blood urea nitrogen, glucose, Serum glutamic oxaloacetic transaminase (aspartate amino transaminase) creatinine, total protein, albumin, alanine aminotransferase, and alkaline phosphatase.

Urine samples were examined for appearance, pH, specific gravity, ketones, protein, urobilinogen and volume.
Sacrifice and pathology:
At termination animals were killed by exanguination under sodium pentobarbital. The weight of the brain, heart, kidney, liver, lungs, testis with epididymis and ovaries were recorded.
Tissues were fixed in 10 % neutral buffered formalin. The following tissues were examined: brain, pituitary, spinal cord, eyes, mandibular salivary gland, thyroid, thymus, trachea, oesophagus, lungs, heart, liver, spleen, kidneys, adrenals, stomach, pancreas, duodenum, jejunum, ileum, colon, cecum, mesenteric lymph nodes, urinary bladder, testes with epididymides, prostate, ovaries, uterus, femur, bone marrow and any unusual lesions. The following tissues were examined microscopically: lungs, liver, kidneys, testes, ovaries, prostate and uterus.
Statistics:
For body weight, food consumption clinical pathology and organ weight data the test groups were compared to the control group using Bartlett’s test for homogeneity of variance followed by one-way ANOVA if the variance was homogenous. Non-homogenous data was log transformed. If ANOVA was significant Scheffe’s multiple pair-wise comparisons of Games and Howell’s multiple pair-wise comparisons were used. All analysis conducted at the 5% probability level.

Results and discussion

Results of examinations

Clinical signs:
effects observed, non-treatment-related
Mortality:
mortality observed, treatment-related
Description (incidence):
1500 mg/kg/day exceeded the MTD and were associated with notable mortality. Deaths were also observed at 300 (1/30) and 700 (3/30) mg/kg/day.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Male body weight was lower than control in all treated groups; there was no similar effect in females.
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:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
In males, some statistically significant differences in organ weights were considered to reflect the reduced body weight, and not a direct effect of treatment. However, liver weight was increased at 300 mg/kg/day and greater and kidney weight at 700 mg/kg/day and greater.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
In animals given 700 or 1500 mg/kg/bw per day there were some changes that were considered to reflect dehydration rather than a direct toxicological change. These included increased packed cell volume and erythrocyte count and increases in total protein and albumin values. There were no urinalysis findings of note. The only change considered to be related to treatment was an increase in blood urea nitrogen values but this was not dose related and the increase above control level was small.
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Lungs: Severe irritation of the bronchial and bronchiolar epithelium with focal sloughing of the respiratory epithelium with histiocytic filling of the eroded foci; peribronchial and peri bronchiolar fibrosis; focal bronchietasis; hyper-secretion of mucous with-in airways often accompanied by mucous lake formation within alveoli; and occasional perivascular and peribronchial aggregates of eosinophils at 700 and 1500 mg/kg. There was no NOEL for the exacerbation of multifocal chronic pneumonitis and focal hyperplasia of bronchial and bronchiolar epithelium. Control animals usually had focal areas of minimal to slight pneumonitis, whereas treated animals more frequently had lesions of moderate severity.
Histopathological findings: neoplastic:
not examined
Other effects:
not specified

Effect levels

open allclose all
Key result
Dose descriptor:
NOAEL
Remarks on result:
not determinable due to adverse toxic effects at highest dose / concentration tested
Key result
Dose descriptor:
LOAEL
Effect level:
50 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Lung pathology: exacerbation of multifocal chronic pneumonitis and focal hyperplasia of bronchial and bronchiolar epithelium apparent in all treated groups

Target system / organ toxicity

Key result
Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Under the study conditions, the LOAEL was considered to be 50 mg/kg bw/day, the lowest dose tested.
Executive summary:

A study was conducted to determine the repeated dose oral toxicity of the test substance when administered to rats daily for 13 weeks. Male and female Fisher rats (15/sex/group) received the substance by oral gavage at dose levels of 0, 50, 100, 300, 700 and 1500 mg/kg bw/day, in olive oil. One group of 15/sex served as the control and received only the vehicle, in volumes comparable to those received by treated groups. Animals were observed daily, body weight and food consumption were measured weekly. Clinical pathology investigations (haematology, clinical chemistry and urinalysis) were conducted prior to termination in Week 13. All animals were subject to a full necropsy and histopathological examination of a comprehensive range of tissues. Following mortalities were recorded during the course of the study: one male in dose group 300 mg/kg bw/day, one male in dose group 700 mg/kg bw/day, two females in dose group 700 mg/kg bw/day, nine females in dose group 1500 mg/kg bw/day. The survival rate of the 1500 mg/kg bw/day dose group males and females was significantly lower than that of the respective control group. Gross pathology findings of lung (hypersecretion of mucous) and stomach alterations were the most notable observations in this dose group. The lung was identified as a target organ and there was no NOEL for the exacerbation of multifocal chronic pneumonitis and focal hyperplasia of bronchial and bronchiolar epithelium, which as observed in all treated groups at a greater severity than in the controls. Comparison of the hematology data between the control and treated groups revealed significantly higher than control value in the mean hematocrit value in the highest dose group males and females and in the mean erythrocyte count in the highest dose group in females. Male body weight was lower than control in all treated groups, there was no similar effect in females. Liver weight was increased at 300 mg/kg bw/day and greater and kidney weight at 700 mg/kg bw/day and greater. No treatment–related effects were noted in comparison of the urinalysis. Under the study conditions, no NOAEL was identified. The LOAEL was considered to be 50 mg/kg bw/day, the lowest dose tested (Wolfe, 1980).

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