Isopentyl acetate

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1973

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented, acceptable publication

Data source

Reference

Reference Type:

publication

Title:

Short-term Toxicity of Isoamyl Alcohol in Rats

Author:

Carpanini FMB Gaunt IF, Kiss IS, Grasso P and Gangolli SD

Year:

1973

Bibliographic source:

Cosmet Toxicol 11: 713-724

Materials and methods

Principles of method if other than guideline:

subchronic oral toxicity study

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

isoamyl alcohol

IUPAC Name:

isoamyl alcohol

Details on test material:

- Name of test material (as cited in data source): isoamyl alcohol

Specific details on test material used for the study:

isoamyl alcohol is equal 3-methylbutan-1-ol

Test animals

Species:

rat

Strain:

other: Ash/CSE

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: obtained from an SPF breeding colony
- Weight at study initiation: mean 94 g (males), 89 g (females)
- Diet: Spillers' Laboratory Small Animal Diet; ad libitum
- Water: tap water; ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 21
- Humidity (%): 50 - 70

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water): normalisation of administered volume
- Concentration in vehicle: 0, 30, 100 and 200 mg per ml per kg bw
- Amount of vehicle (if gavage): 5 ml

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

3, 6 or 17 weeks

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 150, 500 and 1000 mg/kg bw/d
Basis:
other: actual ingested in 17 weeks exposure groups

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 500 and 1000 mg/kg bw/d
Basis:
other: actual ingested in 3 and 6 weeks exposure groups

No. of animals per sex per dose:

10 (in 3 and 6 weeks exposure groups), 30 (in 17 weeks exposure groups)

Control animals:

yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

BODY WEIGHT: Yes
- Time schedule for examinations: initially, at day 5 and then at weekly intervals up to day 110 of the study (consumption of food and water was measured over a 24-hour period preceding the day of weighing).

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At 17 wk, the counts of reticulocytes were confined to control rats and those given the highest dose level (1000 mg/kg)
- Parameters examined: haemoglobin content, packed cell volume and counts of erythrocytes, reticulocytes and total and differential leucocytes

CLINICAL CHEMISTRY: Yes
- Parameters examined: Serum was analysed for the content of urea, glucose, total protein and albumin and for the activities of glutamic-oxalacetic and glutamic-pyruvic transaminases and lactic dehydrogenase.

URINALYSIS: Yes
- Time schedule for collection of urine: collected during week 3, 6 and 13 of treatment
- Parameters were examined: appearance, microscopic constituents and content of glucose, ketones, bile salts and blood. A concentration test was carried out on the same rats involving the measurement of the specific gravity and volume of urine produced in a 6-hr period of water deprivation. In addition, in the groups examined at 6 and 13 wk the same measurements were made on the urine produced during a 2-hour period following a water load (25 ml/kg) and between 16 and 20 hour after the water load.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Results and discussion

Results of examinations

Details on results:

CLINICAL SIGNS AND MORTALITY
One male rat receiving isoamyl alcohol at 1000 mg/kg/day died during wk 8 of the study and one female rat receiving the same level died during wk 10 on test. At autopsy the lung tissue, of both rats, appeared haemorrhagic and there was an excess of fluid in the thoracic cavity. Apart from these two rats, no deaths or abnormalities in behaviour occurred during the study.

BODY WEIGHT AND WEIGHT GAIN
The rate of body-weight gain was lower than the controls in males given 1000 mg isoamyl alcohol/kg daily, so that at week 17 the mean body weight of these treated animals was 9% less than that of the controls. The differences were statistically significant from wk 9 onwards. There were no statistically significant reductions in body-weight gain at other levels in males or at any of the levels of treatment in females.

FOOD EFFICIENCY
The rats given daily doses of isoamyl alcohol gained slightly less weight than the controls fed ad lib but the rate of body-weight gain was similarly reduced in the pair-fed control animals. The average food intake of the treated rats was approximately 1 g/day less than that of the ad lib controls. The organ weights of all three groups were closely similar.

HAEMATOLOGY
The only differences from controls seen in the results of the haematological examinations were some isolated increases in packed cell volume, haemoglobin concentration and erythrocyte count at wk 3 and 6. These were not dose-related and were not seen in both sexes at the same examination.

CLINICAL CHEMISTRY
There were no significant differences between treated and control animals in the results of serum analyses.

URINALYSIS
There were no significant differences between treated and control animals in the results of urinary cell excretion and renal concentration tests. No abnormal constituents were detected in the urine of rats dosed with isoamyl alcohol.

ORGAN WEIGHTS
In male rats dosed with 1000 mg isoamyl alcohol/kg/day for 3 weeks, the weights of most organs and the terminal body weights were significantly lower than those of controls. The males dosed with 500 mg/kg/day for 3 weeks had significantly lower brain, kidney, stomach, small-intestine and testes weights. However, there were no similar differences in the females examined at the same time and when the male organ weights were expressed relative to body weight the only differences seen were in the testes. The only difference in the organ weights after 6 weeks treatment was a lower pituitary weight in male rats receiving 1000 mg isoamyl alcohol/kg/day, a difference which, again, was not evident when the weights were expressed relative to body weight. The organ weights and relative organ weights were similar in test and control rats after treatment for 17 weeks.
In the supplementary study, the testes of the treated rats were no smaller than those of the controls. The reduction in testis weight was not seen in rats treated for 6 or 17 weeks and there was no histopathological evidence of testicular atrophy. Thus it seems likely that the reduced testis weight seen at wk 3 was also a reflection of the difference in body weight.

GROSS PATHOLOGY
At autopsy, there were red patches on the lungs in both sexes at all levels including controls. These were seen mainly at the 3- and 6-wk autopsies.

HISTOPATHOLOGY: NON-NEOPLASTIC
For the 2 animals that died, histopathological examination of the tissues revealed vascular congestion of the lungs, haemorrhage into the alveoli and oil droplets in macrophages. These findings are consistent with accidental dosing by the intratracheal route.
Surviving animals: histopathological examination of the lungs showed only lymphocyte cuffing of the bronchi, the incidence and severity of which were similar in test and control animals. Small cysts in the renal cortex were seen at 17 weeks in three control males and one male at the 1000 mg/kg/day treatment level, and microscopically signs of chronic pyelonephiritis were seen. Small testes were seen in three males in each of the treatment levels examined at, 3 weeks, but the histological appearance of these organs was normal. Small testes were also found in one control male after 17 weeks but in this case there was histopathological evidence of testicular atrophy. One female given 500 mg isoamyl alcohol/kg/day for 17 weeks had a mass, 2-5 cm in diameter, close to the right salivary gland, and on histopathological examination, this proved to be a lipoma. No other abnormalities were seen at autopsy or during the histopathological examination.

Effect levels

1

Dose descriptor:

NOAEL

Remarks:

17 weeks exposure

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects

2

Dose descriptor:

NOEL

Remarks:

17 weeks exposure

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: body weight

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Mean body weight, food consumption and water consumption of rats dosed with 0-1000 mg test substance/kg/day for 110 days:

Dose level (mg/kg/day)	Body weight (g) at day				Weight gain at day 110 (g)	Food consumption (g/rat/day) at day				Mean consumption (ml/rat/day/	Water consumption (ml/rat/day) at day				Mean consumption (ml/rat/day/
	0	33	68	110		0	33	68	110		0	33	689	110
Males
0	95	286	420	487	392	14.1	20.7	18.9	19.5	18.5	18.2	27.5	24.9	25.1	24.1
150	95	281	407	469	374	13.9	20.1	17.7	19.8	19.8	18.7	25.7	22.9	23.9	23.7
500	94	288	408	472	378	13.3	22.7	17.5	18.1	18.1	17.9	30.0	27.8	25.8	25.9
1000	93	266	383*	450*	357*	13.0	19.5	18.1	18.7	17.8	19.2	26.2	27.1	26.1	25.1
Females
0	89	204	258	281	192	12.1	16.9	15.1	16.7	15.4	16.4	21.9	22.0	22.0	21.8
150	90	204	267	293	203	12.5	15.9	15.1	17.2	15.3	18.0	22.5	23.9	21.9	21.5
500	89	202	260	282	193	12.5	15.9	16.5	18.1	15.7	16.7	22.8	24.7	26.5	23.0
1000	88	195	255	284	196	12.8	14.0	14.9	16.6	15.0	16.9	23.2	22.2	23.6	22.7
*P0.05

Body weight and mean food intake of male rats given 0 or 1000 mg isoamyl alcohol/kg/day and of pair fed controls:

Dose level (mg/kg/day)	Diet	Body weight (mean values for groups of 8 rats in g)								Mean food intake (g/rat/day)
		0	3	6	9	11	14	17	20
0	ad lib	65	85	106	124	144	157	179	195	15.9
0	Pair-fed	65	83	105	120	130	146	170	184	14.2
1000	ad lib	64	84	103	121	134	152	175	187	14.8

Applicant's summary and conclusion

Conclusions:

NOEL = 500 mg/kg bw/d (effect on body weight of males at highest dose of 1000 mg/kg bw/d)

Executive summary:

In a published subchronic toxicity study, 10 male and 10 female Ash/CSE rats were treated for 3 and 6 weeks with doses of 500 and 1000 mg/kg bw /day 3-methylbutan-1-ol by gavage (Carpanini et al. 1973). In addition, 30 male and 30 female Ash/CSE rats were treated for 17 weeks with doses of 150, 500 and 1000 mg/kg bw /day. Body weights were determined initially, at day 5 and then weekly. Food and water consumption were determined over a 24-hr period preceding the day of weighing. Urine was collected during week 3, 6, and 13. After sacrifice, haematological examinations, serum analyses, gross and histopathological examinations were performed.

There were no effects associated with 17 weeks of treatment in the results of the haematological examinations, serum analyses, urinary cell counts, renal concentration tests or organ weights. The slightly reduced rate of body-weight gain (9%) observed at week 17 in the males at the highest dose level was shown to be due to a reduced food intake. Although two rats given 1000 mg/kg bw/day died, the histopathological examination showed that these deaths were due to dosing into the lungs and not to any toxic effects.

NOEL = 500 mg/kg bw/d (effect on body weight of males at highest dose of 1000 mg/kg bw/d)

Based on the available and adequate data on the metabolism of isopentyl acetate in the body (see under 7.1 Toxicokinetics, metabolism and distribution) it can be assumed that the ingestion of a certain amount of isopentyl acetate would lead to an equal molar amount of 3-methyl-1-butanol and acetic acid.

Acetic acid is not regarded as toxicologically relelevant compared to 3-methyl-1-butanol. Systemic toxic effects of isopentyl acetate should therefore be found to be the same or similar to the effects of 3-methyl-1-butanol. This study on 3-methyl-1-butanol is therefore regarded as meaningful for the description of repeated dose effects of isopentyl acetate.

All available and adequate data from repeated dose studies was generated by the use of 3-methyl-1-butanol as test substance, administered orally and in one study via subcutaneous route (data entered under IUCLID 7.5.1 + 7.5.4). These data should be regarded together in a weight of evidence approach to evaluate possible toxic effects from the repeated exposure to isopentyl acetate.