(2R,3S)-butane-2,3-diol

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Please find endpoint specific justification in the read-across assessment report.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

assessment report

Cross-reference 2

Reason / purpose for cross-reference:

read-across source

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1978

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

13-week feeding study in non-rodents

GLP compliance:

not specified

Limit test:

no

Species:

dog

Strain:

Beagle

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Central Institute for the Breeding of Laboratory Animals, CBP-TNO, Zeist, The Netherlands
- Age at study initiation: 7-8 weeks
- Weight at study initiation: males: 3.6 to 3.9 kg; females: 2.9 to 3.5 kg (mean body weights of animals per dose group)
- Fasting period before study: no data
- Housing: individually in indoor kennels
- Diet: restricted portion of food twice daily; either 40 g or 50 g food/kg bw/day on different days, but equal for the different dogs on one day
- Water: no data
- Acclimation period: no data
- all dogs had been immunized against distemper

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION
- Rate of preparation of diet: once a week
- Mixing appropriate amounts with (Type of food): basel diet, diets were supplemented with an instant wheat product, glucose and soya bean oil and 1,3-butanediol in such a way that all diets were theoretically isocaloric
- Storage temperature of food: in closed containers at a temperature of 10-15°C

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

daily, two times per day

Dose / conc.:

0 mg/kg bw/day (nominal)

Dose / conc.:

3 mg/kg bw/day (nominal)

Dose / conc.:

6 mg/kg bw/day (nominal)

Dose / conc.:

12 mg/kg bw/day (nominal)

No. of animals per sex per dose:

4 animals per sex per dose group

Control animals:

yes, plain diet

Positive control:

no

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes (behaviour and health)
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- food consumption determined: daily

FOOD EFFICIENCY: No data

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the beginning and at week 2, 6 and 12
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: in all dogs
- Parameters checked: hemoglobin content, packed cell volume, methaemoglobin content, erythrocyte fragility, erythrocytes counts, leucocytes counts, thrombocytes counts, differential white blood cell counts, reticulocytes, Heinz bodies


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the beginning and in week 6 and 12
- Animals fasted: No data
- How many animals: all animals
- Parameters checked: SGPT, SGOT, SAP, total serum protein, serum albumin, fasting blood glucose, blood urea-N, triglycerides, beta-hydroxybutyric acid, acetoacetic acid, plasma free fatty acids, lactate


URINALYSIS: Yes
- Time schedule for collection of urine: at the beginning and in week 6 and 12
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- How many animals: in all dogs
- Parameters checked: appearance, specific gravity, pH, sugar, protein, occult blood, ketones and microscopic examination of the sediment


NEUROBEHAVIOURAL EXAMINATION: No

OTHER:
Analysis of 1,3-butylene glycol in feces was carried out in one male and one female of each group at week 4 by means of liquid chromatography
liver-function test: (bromosuophophthalein method), all dogs of the control and highest dose group at week 13
kidney-function test (phenolred excretion method), all dogs of the control and highest dose group at week 13

Sacrifice and pathology:

After 13 weeks all surviving dogs were anaesthetized by intravenous administratoin of Nembutal followed by exsanguination.

GROSS PATHOLOGY: Yes, each animal immediately after death

HISTOPATHOLOGY: Yes, all animals, Haematoxylin-eosin stained paraffin sections of the organs weighed and also of the following organs and tissues: spinal cord, sciatic nerve, salivary glands, skeletal muscle, thoracic aorta, skin, tonsils, bladder, oesophagus, stomach, duodenum, jejunum, ileum, caecum, colon, pancreas, trachea, circumanal glands, eyes, epididymis, prostate, uterus, gall bladder, tongue and thymus. Special attention was paid to possible occurence of lipofuscin in various tissues.

Other examinations:

ORGAN WEIGHTS: heart, kidneys, liver, spleen, lungs, testicles/ovaries, pituitary, thyroids, adrenals and brain

Statistics:

Wilcoxon test

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):

no effects observed

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
An epileptic seizure was observed in one dog of the top-dose group during the third week. From that time the number of dogs with epilepsy-like symptoms and the frequency of the attacks increased gradually in the two highest dose groups both in males and females. The phenomen was easily induced by disturbing the animals.

BODY WEIGHT AND WEIGHT GAIN
In the two highest dose groups weight gain was clearly less than in the controls. This effect was statistically significant at 9000 and 12000 mg/kg bw/day in males and at 12000 mg/kg bw/day in females.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
The daily portion was consumed completely by all dogs.

HAEMATOLOGY
Hematological effects were only seen in thrombocyte counts and methaemoglobin. Thrombocyte counts were increased in the groups receiving 9000 and 12000 mg/kg bw/day at all stages, although in the group receiving 9000 mg/kg bw/day the increase was not statistically significant at week 12. The increased thrombocyte counts observed with 6000 mg/kg bw/day at weeks 6 and 12 were regarded as not treatment-related. Increased levels of methaemoglobin were observed at the high dose group at all stages. The effect was statistically significant at week 12.

CLINICAL CHEMISTRY
Biochemistry changes consisted of a slight, but dose-related increase in SGPT at the two highest doses, increased SGOT in the top dose group at 6 weeks but not at week 12, and a dose-related increase in free fatty acid that was statistically significant only at the high dose. Blood levels of beta-hydroxy butyric acid, acetoacetic acid and lactate increased with increasing feeding levels of BD. Small quantities of BD were recovered from faeces of dogs fed 9000 or 12000 mg/kg bw/day.

URINALYSIS
Values for pH in urine of dogs of the two highest dose groups were lower than in the other groups at week 7. Slight ketonuria was observed in dogs of the top-dose group at week 12.

ORGAN WEIGHTS
The relative weights of the kidneys, liver, brain, adrenals and lungs were statistically significantly increased in dogs of the top-dose group, the relative weights of the thymus and spleen were decreased. The relative weights of the liver and kidneys were also increased at 9000 mg/kg bw/day.

GROSS PATHOLOGY
Gross examination of the female dog from the 9000 mg/kg bw/day dose group that died during the study revealed a congenital heart defects (persistent ductus arteriosis). No other treatment attributable effects were observed.

HISTOPATHOLOGY
No treatment related histopathological effects were observed.

Key result

Dose descriptor:

NOAEL

Effect level:

6 000 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: changes in behaviour, haematology, blood biochemistry, organ weights and growth rate

Dose descriptor:

LOAEL

Effect level:

9 000 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: changes in behaviour, haematology, blood biochemistry, organ weights and growth rate

Critical effects observed:

not specified

Conclusions:

In this subchronic feeding study in dogs treatment-related effects occurred only at 9000 and 12000 mg/kg bw/day. It is therefore concluded that 6000 mg/kg bw/day was a no-toxic effect level in the present study.

Executive summary:

In a subchronic (13-week) feeding study dogs were fed with a diet containing 1,3-butylene glycol, resulting in intake levels of 0, 3000, 6000, 9000 and 12000 mg/kg bw/d (Reuzel et al., 1978). Epilepsy-like seizures were frequently observed in dogs fed 9000 or 12000 mg of the test item/kg bw/d. Body weight gain was depressed in dogs fed 9000 or 12000 mg/kg bw/d. Thrombocyte counts were increased at 6000 mg/kg bw/d and above. Methaemoglobin was elevated in dogs of the top-dose group only. Blood levels of free fatty acids, beta-hydroxy butyric acid, aceto-acetic acid and lactate increased with increasing feeding levels of the test item. Kidney and liver function was not affected. Slight ketonuria was observed in dogs of the top-dose group at week 12. Small quantities of the test item were recovered from feces of dogs fed 9000 or 12000 mg/kg bw/d. The relative weights of the liver and adrenals showed dose-related increases in the two highest dose groups. In addition, the top-dose group showed increased relative weights of the kidneys, brain and lungs and decreased relative weights of the thymus and spleen. Gross and microscopic examination failed to reveal any changes that could be ascribed to treatment. The NOAEL in the present study was 6000 mg/kg bw/d.

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

(2R,3S)-butane-2,3-diol

EC Number:

823-920-1

Cas Number:

5341-95-7

Molecular formula:

CH3CH(OH)CH(OH)CH3

IUPAC Name:

(2R,3S)-butane-2,3-diol

Test material form:

liquid

Results and discussion

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

6 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: changes in behaviour, haematology, blood biochemistry, organ weights and growth rate

Remarks on result:

other: Effect conc. are identical for the submission substance, because target and source substance have the same MW.

2

Dose descriptor:

LOAEL

Effect level:

9 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: changes in behaviour, haematology, blood biochemistry, organ weights and growth rate

Remarks on result:

other: Effect conc. are identical for the submission substance, because target and source substance have the same MW.

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Dogs treatment-related effects occurred only at 9000 and 12000 mg/kg bw/day. It is therefore concluded that 6000 mg/kg bw/day was the no-toxic effect level.

Executive summary:

The study used as source investigated sub-chronic toxicity over a 13 weeks period in dogs. The study results of the source compound were considered applicable to the target compound in a WoE approach, and were used for classification and labelling acc. to Regulation (EC) No 1272/2008. Justification and applicability of the read-across approach (structural analogue) is outlined in the read-across report in section 13.