L-threonine

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP range-finding study for OECD407 study.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Guideline:

other: dose-range-finding study for OECD Guideline 407 study

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

L-threonine

EC Number:

200-774-1

EC Name:

L-threonine

Cas Number:

72-19-5

Molecular formula:

C4H9NO3

IUPAC Name:

L-threonine

Test animals

Species:

rat

Strain:

other: CD / Crl: CD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: males 40-44 days, females 40-44 days
- Weight at study initiation: males 106.2-123.3 g, females 104.1-121.4 g
- Housing: individually
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C +/- 3°C
- Humidity (%): 55% +/- 15%
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: 0.5% aqueous hydroxypropylmethylcellulose gel

Details on oral exposure:

The test substance was dissolved in 0.5% Methocel to the appropriate concentrations and was administered orally by gavage, at a constant volume of5 ml/kg b. w. daily for 14 days. The control animals received 5 ml vehicle/kg b. w. daily for 14 days in the same manner. The amount of the test
substance was adjusted to the animal's actual body weight daily. The test substance was freshly prepared every day.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

For each test substance that is mixed with a vehicle, tests by appropriate analytical method will be carried out for the main study (see LPT protocol
no. 16091 /02) to determine the concentration and stability of the test substance in the mixtures:
The analysis of the test substance-vehicle mixtures showed that the concentrations of the test substance-vehicle mixtures were in the range from 71.5% to 86.6% of nominal values after preparation. The slightly lower yields as expected ( 100% ± 20%) are probably related to analytical difficulties with the matrix Methocel.

Duration of treatment / exposure:

2 weeks

Frequency of treatment:

once daily, 7 days per week for 2 weeks

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
control: 5 mL vehicle/kg b.w./day
Basis:
actual ingested

Doses / concentrations 2

Remarks:

Doses / Concentrations:
300 mg/kg b.w./day
Basis:
actual ingested

Doses / concentrations 3

Remarks:

Doses / Concentrations:
600 mg/kg b.w./day
Basis:
actual ingested

Doses / concentrations 4

Remarks:

Doses / Concentrations:
1000 mg/kg b.w./day
Basis:
actual ingested

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

Rationale for dose selection:
The dose Ieveis for this preliminary study were selected in agreement with the sponsor based on available toxicity data.

Examinations

Observations and examinations performed and frequency:

Clinical signs:
Individual animals were observed at least once daily for any signs of behavioural changes, reaction to treatment or illness. lmmediately after
administration any signs of illness or reaction to treatment were recorded for each individual animal. Cageside observations included: general
appearance including changes in skin/fur, eyes, mucous membranes; respiratory and circulatory systems, somatomotor activity and behaviour
patterns. The onset, intensity and duration of any signs were recorded. ln addition, animals were checked regularly throughout the working day from 7.00 a.m. to 3.45 p.m. On Saturdays and Sundays animals were checked regularly from 7.00 a.m. to 11.00 a.m. with a final check performed at
approximately 1.00 p.m. Dated and signed records of appearance, change and disappearance of clinical signs were maintained on clinical history
sheets for individual animals.
Mortality:
Further checks were made early in each working day and again in the afternoon to Iook for dead or moribund animals. This allowed post mortem
examination to be carried out during the working period of that day. On Saturdays and Sundays a similar procedure was followed except that the
final check was carried out at approximately 1.00 p.m.
Body weight:
The body weight of each rat was recorded at the time of allocation of animals to groups, on the day of commencement of treatment and once a
week thereafter always on the same day of the week throughout the experimental period.

Sacrifice and pathology:

On test day 15 (24 hours after the last test substance administration) all animals were sacrificed under ether narcosis by cutting the aorta
abdominalis, weighed, dissected and inspected macroscopically under the direction of a pathologist. All superficial tissues were examined visually
and by palpation and the cranial roof removed to allow observation of the brain, pituitary gland and cranial nerves. After ventral midline incision and skin reflection all subcutaneous tissues were examined. The condition of the thoracic viscera was noted with due attention to the thymus, lymph
nodes and heart. The abdominal viscera were examined before and after removal, the urinary bladder was examined externally and by palpation. Thegastro-intestinal tract was examined as a whole and the stomach and caecum were incised and examined. The lungs were removed and all pleural
surfaces examined under suitable illumination. The liver and the kidneys were examined. Any abnormalities in the appearance and size of the gonads, adrenals, uterus, intra-abdominal lymph nodes and accessory reproductive organs were recorded.

Results and discussion

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Mortality:

None of the rats died prematurely.

Clinical signs:

The treatment with 300, 600 or 1000 mg L-threonin/kg b.w./day for 2 weeks did not show any influence on behaviour and external appearance of rats. None of the rats died prematurely.

Body weight:

No test substance-related influence was observed on the body weight of the male and female rats treated with any of the tested dose Ieveis (300, 600 or 1000 mg L-Threonin/kg b.w./day).

Food and drinking water consumption:

No influence was noted on food intake for the male and female rats treated with either 300, 600 or 1000 mg L-Threonin/kg b.w./day. No test substance-related influence was noted on the drinking water consumption.

Macroscopic post mortem findings:

The macroscopic post mortem examination on test day 15 did not reveal any test substance-related findings in animals treated with 300, 600 or 1000 mg L-Threonin/kg b.w./day.