2-methylpropyl-(R)-2-hydroxypropanoate

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Publication. Study conducted in accordance to OECD guideline 408. 2-methyl-1-propanol was used for read-across to isobutyl-R-lactate.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1997

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Limit test:

no

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

Constituent 2

Reference substance name:

Isobutanol

IUPAC Name:

Isobutanol

Test material form:

other: liquid

Details on test material:

- Name of test material (as cited in study report): 2-methyl-1-propanol (MEP)
- 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 Thomae GmbH, Biberach/Riss, Germany
- Age at study initiation: 6 weeks
- Weight at study initiation: mean body weight male: 172 g, female: 147 g
- Housing: Individually in stainless steel wire mesh cages (type DK III)
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum

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 drinking water solutions were prepared freshly twice a week. To ensure homogenity of the solutions of the test substance in the drinking water, each mixture was stirred for about 30 min using a magnetic stirrer.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Stability and homogeneity of the test substance in the drinking water was analysed over a period of 6 days. To check for the applied concentrations 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:

ad libitum (as drinking water solutions)

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 1000, 4000, 16000 ppm
Basis:
nominal in water

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 80, 340, 1450 mg/kg/d
Basis:
nominal in water

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
Based on the results of of a dose range finding study to check for palatability 16000 ppm was selected as maximum dose to avoid this complication.

Positive control:

N.A.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

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 :
Food consumption were determined once a week

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

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Prior to the beginning of treatment and at the termination of the animals by using an ophthalmoscope.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on day 87 of the study. Blood was taken from the retroorbital venous plexus
- Animals fasted: No data
- How many animals: 10 animals/sex/dose
- Parameters examined were: white blood cells, red blood cells, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelets, reticulocytes, differential blood count and prothrombin time

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on day 87 of the study. Blood was taken from the retroorbital venous plexus
- Animals fasted: No data
- How many animals: 10 animals/sex/dose
- Parameters examined were: sodium, potassium, chloride, inorganic phosphate, calcium, glucose, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, serum-glutamyltransferase, urea, albumin, blood creatinine, total bilirubin, total protein, globulins, triglycerides, cholesterol

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
After sacrification, the animals were 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. Organs or tissues required by guidelines as well as gross lesions were fixed in a 4% formaldehyd solution.

HISTOPATHOLOGY: Yes
Histological examinations and assessment of the findings were carried out after histotechnical processing and staining with hematoxylin and eosin.

Other examinations:

None

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):

No effects on mortality and clinical signs occurred.

Mortality:

no mortality observed

Description (incidence):

No effects on mortality and clinical signs occurred.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

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

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

No treatment related effects. Histopathological changes of the testes (tubular degeneration and diffuse hyperplasia of Leydig’s cells), the spleen (minimal increase in extramedullary hematopoiesis) or the kidneys (dilation of the renal pelvis) occurred sporadically in control and/or animals treated with MEP.

Histopathological findings: neoplastic:

not examined

Other effects:

not specified

Effect levels

Dose descriptor:

NOAEL

Effect level:

16 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects at highest dose.

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 1: Effective test substance intake
Test group		MEP concentration in drinking water (p.p.m.)		Mean daily substance intake (mg/kg bw)
				males		females
1		1000		75		91
2		4000		300		385
3		16000		1251		1657

Applicant's summary and conclusion

Conclusions:

The NOAEL of 2-methyl-1-propanol after oral administration via the drinking water over a period of 90 days is considered to be 16000 ppm for both sexes.

Executive summary:

A repeated subchronic oral dose toxicity study (OECD 408) was conducted using male and female Wistar rats at doses of 0, 1000 ppm (about 80 mg/kg/d), 4000 ppm (about 340 mg/kg/d), and 16000 p.p.m. (about 1450 mg/kg/day) of 2-methyl-1-propanol (99.8% purity). The animals received the test item daily over a period of 90 days via the drinking water. The test substance had no effect on mortality, food consumption, water consumption, body weight, haematological and clinical chemistry examinations and on pathological findings. Based on the results reported the NOAEL for orally administered 2-methyl-1-propanol via the drinking water is considered to be 16000 p.p.m. (about 1450 mg/kg bw/day) for both sexes.

This study in rats is acceptable and satisfies the principle requirement for a repeated oral dose toxicity study according to OECD 408 in rats. Due to the fact that isobutanol is a degradation product of isobutyl lactate, this result is relevaant for risk assessment.