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Toxicological information

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:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This study is classified as reliable with restrictions even though it is not noted whether the study followed GLPs and was not conducted in accordance with guidelines. This is because the study’s goal was to examine nephrotoxicity, not systemic toxicity as outlined in OECD guideline 407. Study methods are well-documented and scientifically sound.
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1985

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study’s goal was to examine nephrotoxicity, not systemic toxicity as outlined in OECD guideline 407. When comparing the study's methods to OECD 407, the following limitations were noted: no female rats were tested; only two dose groups were tested at fairly high doses for a substance that can be aspirated; the only post-necropsy examinations were of the kidney.
GLP compliance:
not specified
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
2-methylbutane
EC Number:
201-142-8
EC Name:
2-methylbutane
Cas Number:
78-78-4
Molecular formula:
C5H12
IUPAC Name:
2-methylbutane
Details on test material:
- Name of test material (as cited in study report): 2-methylbutane
- Substance type: C5 aliphatics
- Analytical purity: not reported

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, New York
- Age at study initiation: 9 weeks
- Weight at study initiation: 171 to 194 grams
- Fasting period before study: not reported
- Housing: individual, suspended polycarbonate cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24 to 26 degrees celsius
- Humidity (%): 40 to 80 %
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): 12 hours dark and 12 hours light

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: calculated based on body weights taken prior to dosing on day 1, appropriate dosing volume was determined using specific gravity
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
4 weeks
Frequency of treatment:
once daily, 5 days per week
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0.5 g/kg/day
Basis:
no data
Remarks:
Doses / Concentrations:
2.0 g/kg/day
Basis:
no data
No. of animals per sex per dose:
10
Control animals:
yes
Details on study design:
- Dose selection rationale: pilot study
- Negative control: isotonic saline at a dose of 2.0 g/kg/day
Positive control:
Unleaded gasoline

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: yes
- Time schedule: twice daily

BODY WEIGHT: yes
- Time schedule for examinations: prior to dosing and at scheduled sacrifice

FOOD EFFICIENCY: not reported

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): no

OPHTHALMOSCOPIC EXAMINATION: no

HAEMATOLOGY: no

CLINICAL CHEMISTRY: no

URINALYSIS: no

NEUROBEHAVIOURAL EXAMINATION: no
Sacrifice and pathology:
GROSS PATHOLOGY: yes (stated, no data provided)
HISTOPATHOLOGY: yes (kidney only)
Statistics:
mean and standard deviations calculated for body weight, kidney weight, and kidney pathology data; statistical significance calculated using Studen t-test and Mann-Whitney U test

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):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
MORTALITY
10% of low dose rats, 90% of high dose rats

TERMINAL BODY WEIGHT
significantly lower than saline control at the low dose (p < 0.05), not calculated at high dose due to high mortality

KIDNEY WEIGHTS
not significantly different than controls at low dose, not calculated at high dose due to high mortality

GROSS PATHOLOGY
no effects

HISTOPATHOLOGY: KIDNEY
not significantly different than controls at low dose, not calculated at high dose due to high mortality

Effect levels

Dose descriptor:
NOAEL
Remarks on result:
not determinable
Remarks:
no NOAEL identified

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The results for 2-methylbutane and saline (i.e., the control) were not significantly different. 2-methylbutane was found to cause high mortality at 2.0 g/kg/day.
Executive summary:

The nephrotoxicity of 2-methylbutane was evaluated in male F344 rats over 4 weeks after oral gavage doses of 0.5 g/kg/day and 2.0 g/kg/day. Clinical examinations were conducted twice daily throughout the study, and nephrotoxicity and histopathology of the kidney were evaluated at termination. The results were compared to positive and negative controls. Statistical methods used were appropriate. 

Mortality occurred in 90% of high-dose rats and 10% of low-dose rats. Kidney weights for surviving animals were comparable to controls. 2 -methylbutane's ability to cause hydrocarbon nephropathy was comparable to the saline control (not significantly different).

This study is classified as reliable with restrictions, Klimisch score 2, even though it is not noted whether the study followed GLPs and was not conducted in accordance with guidelines. This is because the study’s goal was to examine nephrotoxicity, not systemic toxicity as outlined in OECD guideline 407. Study methods are well-documented and scientifically sound. However, several study limitations are noted when comparing this study’s methods to OECD 407. First, no female rats were used in the study. Second, the selected dose levels did not cover an appropriate range (i.e., only two dose groups were used, and both were at fairly high doses for a substance that can be aspirated). Third, the substance was administered 5 days/week instead of 7. Fourth, body weight measurements were only taken twice during the experiment (i.e, prior to dosing and at the scheduled sacrifice). Fifth, the only post-necropsy examinations were of the kidney. Finally, functional observations, hematology analysis, urinalysis and other post-necropsy examinations were were conducted.