Isobutyraldehyde

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1990

Report date:

1990

Reference 2

Reference Type:

other: study report amendment

Title:

Unnamed

Year:

1991

Report date:

1991

Reference 3

Reference Type:

publication

Title:

Subchronic toxicity studies of 3-Methyl-1-butanol and 2-Methyl-1-propanol in rats

Author:

Schilling K. et al.

Year:

1997

Bibliographic source:

Human & Experimental Toxicology (1997) 16, 722-726

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2-methylpropan-1-ol

EC Number:

201-148-0

EC Name:

2-methylpropan-1-ol

Cas Number:

78-83-1

Molecular formula:

C4H10O

IUPAC Name:

2-methylpropan-1-ol

Details on test material:

- Name of test material (as cited in study report): 2-Methyl-1-propanol
- Physical state: liquid
- Analytical purity: 99.8 %

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Dr. Karl Thomae GmbH
- Age at study initiation: 42 days
- Weight at study initiation: mean males: 172g; mean females: 147 g
- Housing: individually
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 6 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24 °C
- Humidity (%): 30-70 %
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
The test substance was weighed for each particular test group and the specific quantity of drinking water (also weighed) added. To obtain a homogeneous solution of the test substance in the drinking water the mixture was then stirred for about 30 minutes using a magnetic stirrer.
The drinking water solutions were prepared twice a week.
The drinking bottles were filled using a semi-automatic metering device (Fortuna Optifix).

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analytical investigations were carried out to characterize the stability and homogeneity of test substances in drinking water and to verify the target concentrations. The homogeneity of the test substances was guaranteed by the high degree of purity. The stability and the homogeneity of the test substances in the drinking water over a period of 6 days were analyzed. To check the correctness of the target concentration in drinking water, a sample of each concentration was taken for analysis by capillary gas chromatography at the beginning and at the end of the application period.

Duration of treatment / exposure:

90 days

Frequency of treatment:

continuous

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 1000, 4000, or 16,000 ppm
Basis:
nominal in water

Doses / concentrations 2

Remarks:

Doses / Concentrations:
approx. 80, 340, or 1450 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
In a test study n which 2-Methyl-1-propanol and a similar substance in doses of 0 and 20000 (first 2 weeks) resp. 16000 ppm (next 2 weeks) were administered to each of 3 rats/sex the following observations, covering the entire study period, were made:
- No substantial differences as to the body weight gain and feed consumption of both sexes.
- The drinking water consumption of the males (20000 ppm) had increased by about 16% around the end of week 2 of the study; at the end of the test study, after the dose had been reduced to 16000 ppm, the increase recorded was even as high as about 43% compared to control.
- After a 14-day administration of 20000 ppm, the drinking water consumption of the females had decreased by about 16%; after the concentration had been changed to 16000 ppm, the situation at the end of the study was different, as the drinking water consumption was by about 15% higher than the control value.
- The gross-pathological examinations established no differences between the control animals and the rats which received the test substance.

On the basis of the data above and to guarantee a procedure parallel to the study with a similar substance the following doses with the factor 4 were chosen for the subchronic study with administration of the test substance via the drinking water:
1000 ppm: as the no adverse effect level to be expected
4000 ppm: as the dose with marginal toxic effects or as guarantee of a higher no adverse effect level
16000 ppm: as the dose with toxic effects to be expected

Positive control:

no data

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS/DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animals were examined at least once daily for clinical signs and mortality. The animals were subjected once a week to an additional exact clinical examination.

BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were recorded at the beginning of the study and weekly throughout the study.

FOOD CONSUMPTION:
- Time schedule for examinations: Food consumption were determined once a week for a period of 7 days.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: Water consumption was determined once a week for a period of 4 days. The mean daily intake of the test substances (in mg per kg body weight) was calculated at the intervals at which water consumption was determined.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Ophthalmological examinations were carried out prior to the beginning of treatment and at the termination of the studies using an ophthalmoscope.
- Dose groups that were examined: Control animals and high dose group

HAEMATOLOGY: Yes
- Time schedule for collection of blood: blood was taken on day 87 of the study
- Anaesthetic used for blood collection: No
- Animals fasted: No
- How many animals: all surviving animals per test group and sex
- Parameters examined: white blood cells, red blood cells, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelets, reticulocytes, differential blood count, prothrombin time

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: blood was taken on day 87 of the study
- Animals fasted: No
- How many animals: all surviving animals per test group and sex
- Parameters examined:sodium, potassium, chloride, inorganic phosphate, calcium, glucose, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, serum-gamma-glutamyltransferase, urea, albumin, blood creatinine, total bilirubin, total protein, globulins, triglycerides, cholesterol

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
For post-mortem examinations at the end of the 90-day treatment period, the animals were killed, necropsied and assessed by gross pathology. The weight of the anesthetized animals and the weights of their livers, kidneys, adrenal glands and testes were determined.
HISTOPATHOLOGY: Yes
Organs or tissues required by guidelines as well as all gross lesions were fixed in a 4% formaldehyde solution. Histological examination and assessment of the findings were carried out after histotechnical processing and staining with hematoxylin and eosin.

Statistics:

Mean values and standard deviations were calculated for body weight, food and water consumption, intake of the test substances, hematological and clinical chemistry parameters as well as for absolute and relative organ weights. The organ weights were statistically evaluated using the DUNNETT's test for comparison of the dose groups with the control groups. The analysis of variance (ANOVA) with subsequent DUNNETT's test was used to compare the body weights as well as the hematological and clinical biochemistry data of the dose groups with those of the control groups.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

All animals participating in the study were essentially free from clinical signs. Only one animal (4000 ppm) showed reddish smear on one eye and another animal (16000 ppm) were found to have an increased urine section, an increased drinking water consumption and at palpation apparently enlarged kidneys. These effects were assessed as being not substance-induced, i.e. incidental and spontaneous in nature.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

After 42 days of the study one control animal (0 ppm, male) was found dead in the cage. Otherwise no further animal died intercurrently during the entire study.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

The body weight gain of all dosed animals of both sexes was, within the biological limits, analogous to the controls.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

The males of test group 1 (1000 ppm) showed in the course of the second half of the study a marginal increase in the feed consumption values being significant only in some cases. The females of the same group showed throughout the study isolated cases where the feed consumption was slightly increased. Apart from these findings there were no effects on the feed consumption of the males and females of test groups 2 (4000 ppm) and 3 (16000 ppm).
In respect to the isolated occurrence and the lack of a dose-response relationship, the increase in the feed consumption is assessed as being incidental in nature.

Water consumption and compound intake (if drinking water study):

effects observed, non-treatment-related

Description (incidence and severity):

Throughout the course of the study, an increase in the drinking water consumption of males and females of test groups 1 (1000 ppm), 2 (4000 ppm) and 3 (16000 ppm) was observed sporadically. It varied within the test groups, showed no clear dose-response relationship and was only evident in few animals over the whole study period.
In respect to this, the sporadically increased drinking water consumption was assessed as being not substance induced.
The amount of test substance intake (in mg) consumed each day by the animals per kilogram body weight was calculated at the times at which the drinking water consumption was also determined.
males (1000 ppm): ca. 75 mg/kg bw/day; females (1000 ppm): ca. 91 mg/kg bw/day
males (4000 ppm): ca. 300 mg/kg bw/day; females (4000 ppm): ca. 385 mg/kg bw/day
males (16000 ppm): ca. 1251 mg/kg bw/day; females (16000 ppm): ca. 1657 mg/kg bw/day

Ophthalmological findings:

no effects observed

Description (incidence and severity):

The ophthalmological examinations carried out before the beginning of administration and towards the end of the study using a hand-held slit lamp revealed no substance induced impairment of the refracting media.
All examinations revealed no differences between treated and untreated animals.

Haematological findings:

no effects observed

Description (incidence and severity):

The oral administration of 2-Methyl-1-propanol in doses of 1000; 4000 and 16000 ppm via the drinking water for 3 months to male and female rats caused no changes related to the test substance either in the clinicochemical or in the hematological examinations.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

The oral administration of 2-Methyl-1-propanol in doses of 1000; 4000 and 16000 ppm via the drinking water for 3 months to male and female rats caused no changes related to the test substance either in the clinicochemical or in the hematological examinations.

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

The mean absolute and relative testes weights of the animals of dose group 3 (16000 ppm) were slightly decreased when compared with the corresponding control group and they were below the mean weights of 13 historical control studies. However, this weight decrease was not statistically significant. The individual absolute and relative testes weights of the two animals with gross lesions were far below those of all other treated and untreated animals of the study.The mean absolute and relative testes weights of the remaining 8 animals of dose group 3 (16000 ppm) were comparable to the controls and to those of the historical control data of 14 comparable studies.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

The gross pathology revealed that 2 animals in group 3 (16000 ppm) had small testes, and this was marked and moderate for the animals respectively.
With respect to the results obtained during histopathological examination, it appears rather unlikely that the testicular findings of two animals of dose group 3 (16000 ppm) represent an effect of the test substance. The spontaneous origin of the observed tubular degeneration is supported by the fact that focal tubular degeneration was also noted in one control male whereas no precursor lesions were observed in any of the other treated animals of the high dose group. Moreover, neither the reduced absolute or relative testes weights of this group were statistically significantly altered nor did the mean values of the remaining grossly and histopathologically unaffected 8 animals of this group show any biologically relevant deviation from the controls.

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

The histopathology of these testes revealed diffuse tubular degeneration and diffuse hyperplasia of Leydig's cells. Both these changes were moderate and slight in the animals respectively. The testis of 1 control animal was found to have slight focal tubular degeneration. It appears unlikely that this is an effect of the test substance, especially since the testis weights of the animals in group 3 (16000 ppm) were not statistically significantly different from those in the control group nor were there any lesions in the testes of these animals. The spontaneous origin of the observed tubular degeneration is supported by the fact that focal tubular degeneration was also noted in one control male whereas no precursor lesions were observed in any of the other treated animals. No other alterations of the testicles were noted in any of the other treated or control animals histopathologically.

A minimal increase in extramedullary hematopoiesis was noticed in the spleen of 5 male control animals and 4 males in group 3 (16000 ppm). The same was found in 1 female control animal and 5 females in group 3 (16000 ppm). However, this cluster of findings in the females in group 3 is not regarded as related to the test substance, especially since there was no such clustering in the males in group 3 and there were no corresponding changes found in the hematology.

1 female in group 3 (16000 ppm) had very high kidney weights (10.95 g). The gross pathology of both kidneys revealed several cysts with a diameter up to 15 mm. The histopathology of these kidneys showed extreme dilation of the renal pelvis. These changes are an incidental finding, and an effect of the test substance can be ruled out.

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Effect levels

Dose descriptor:

NOAEL

Effect level:

> 1 450 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects observed

Remarks on result:

other: original value: 16000 ppm

Target system / organ toxicity

Critical effects observed:

no