2-aminopyridin-3-ol

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19.10.2004 - 02.05.2005

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.26 (Sub-Chronic Oral Toxicity Test: Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Test material

Test material information

1

Reference substance name:

2-aminopyridin-3-ol

EC Number:

240-886-8

EC Name:

2-aminopyridin-3-ol

Cas Number:

16867-03-1

Molecular formula:

C5H6N2O

IUPAC Name:

2-aminopyridin-3-ol

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Age at delovery: about 6-7 weeks
Age at the first administration: about 7-8 weeks
Range of the body weights: At the start of the study a maximum deviation of 20 % of any individual body weight from the mean of the sex concerned is accepted.
Number of animals (main study): 90 males and 90 females. Females were non pregnant and nulliparous.
Health status: The animals were ordered in a specified pathogen free (SPF) status, shipped in filter cages (main study only) and subjected to a health check prior to the first dosing.

Conditions:
Room temperature: Average of 22.0 °C (continuous control and recording).
Relative humidity: Average of 55.9 % (continuous control and recording).
Air exchange: 12/h.
Light: Artificial light from 6 a.m. to 6 p.m.
Cages: Single caging.
Bedding material: Aspen wood chips
Food: Ad libitum
Water: Ad libitum, tap water
Acclimatisation: 14 days.

Administration / exposure

Route of administration:

oral: gavage

Details on route of administration:

dose volume: 10 mL/kg bw.
The individual dose volumes were calculated using the last determined body weights.

Vehicle:

other: deionised water

Duration of treatment / exposure:

males: 91 days
females: 92 days

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

group K, vehicle control

Doses / concentrations 2

Dose / conc.:

30 mg/kg bw/day (nominal)

Remarks:

group A

Doses / concentrations 3

Dose / conc.:

60 mg/kg bw/day (nominal)

Remarks:

group B

Doses / concentrations 4

Dose / conc.:

120 mg/kg bw/day (nominal)

Remarks:

group C

No. of animals per sex per dose:

20

Control animals:

yes, concurrent vehicle

Results and discussion

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

behaviour (functional findings)

body weight and weight gain

clinical biochemistry

food consumption and compound intake

gross pathology

haematology

histopathology: neoplastic

mortality

ophthalmological examination

organ weights and organ / body weight ratios

urinalysis

water consumption and compound intake

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The test substance caused several effects in addition to unspecific alterations in body weights, food consumption, clinical chemistry and organ weights:

In life, there were erratic cases of transient "seizures", characterised by convulsions, vocalisation and salivation. The alterations were rare, but severe and twice lethal. In spite of their rare occurrence, they are considered as important test substance related effects.

Histopathologically, there were liver changes (foci of hepatocellular necrosis), interpreted as secondary effects to unidentified primary ones and considered to be test substance related effects.

None of the alterations noted gives an indication for a mode of action or a specific target system or target organ. Nevertheless, the effects of the test substance became life threatening.

There was no pronounced sex difference in the response to the test substance, though mortality was noted in females only, but severe clinical changes were present in both sexes.

Test substance related alterations were noted in the mid and the high dosed group, while none were found in the low dosed group.

The changes noted were reversible during the recovery period.

The "No-Observed-Effect-Level" (NOEL) of "A-132" was therefore at 30 mg per kg body weight and day.

Executive summary:

SUMMARY

Aim of the study

This study was performed to evaluate the toxicity of "A 132" after a repeated oral administration to rats, according to the  

•       Directive 2001/59/EC B.26, "Subchronic Oral Toxicity", 21. August 2001;

•       OECD-Guideline 408, "Repeated Dose 90-Day Oral Toxicity Study in Rodents", 21. Sept. 1998.

Methods

Test substance administration:

The test substance was administered as a solution in deionised water, orally by gavage to 3 groups of 20 male and 20 female Wistar rats each, once a day for 91 (males) or 92, (females) consecutive days (Day 1 to Day 91/92).

Doses used:

•       Group A (low dose):  30 mg "A 132" per kg body weight and day,

•       Group B (mid dose): 60 mg "A 132" per kg body weight and day,

•       Group C (high dose): 120 mg "A 132" per kg body weight and day.

An equally sized negative control group (group K) received the vehicle for the test substance.

The dose volume was uniformly 10 mL per kg body weight.

In addition, two groups of 5 males and 5 females each, i.e. one high dose satellite group

(group CS) and one control satellite group (group KS), were treated in the same way as their corresponding groups, but were kept for further 28 days without a test substance administration in an attempt to observe the reversibility or persistence of test substance induced lesions.

Investigations:

•       Animal observations: All animals, once a day (plus a daily check for viability).

•       Detailed clinical observations: All animals, once a week.

•       Functional observations: Day 89 (males) and Day 90 (females).

•       Ophthalmoscopy: All animals, Day -5 and Day 85

•       Body weights: All animals, once a week.

•       Food consumption: All animals, for each week.

•       Haematology: All animals of groups K, A, B and C at the end of the dosing period (Males on Day 91, females on Day 92); all animals of groups KS

and CS on Day 120.

•       Clinical biochemistry: Same animals and terms as for haematology.

•       Necropsy with gross pathological examination: All males of groups K, A, B and C on Day 91, all females of groups K, A, B and C on Day 92, all

animals of groups KS and CS on Day 120.

•       Organ weight determination: Selected organs of all animals at necropsy.

•       Histopathological examination: Selected organs of all animals of groups K and C plus all gross lesions.

Results:

•       Mortality:

2 low dosed animals were lost due to a watering system failure.

2 high dosed females were found dead. Their death is considered to be test substance related, though no cause of death could be identified by post mortem examination.

•       Observations in life, clinical and functional observations:

In high dosed animals "seizure"-like abnormalities, with clonic convulsions, vocalisation and salivation in a few, short lasting cases. In addition, a few signs of reduced well-being were noted in mid and high dosed animals.

•       Ophthalmoscopy:

No test substance related findings.

•       Body weights and food consumption:

Body weights of high dosed males and females, body weight gain of mid and high dosed males and high dosed females were significantly reduced at some examination terms Food consumption of mid and high dosed females was reduced on single terms.

•       Haematology, clinical chemistry and organ weights:

There were several statistically significant differences in haematology (MCV, MCH, blood cell counts, haematocrit), in clinical biochemistry (ALT, AST, K+, total protein, cholesterol) and in organ weights (kidneys, thymus, heart, liver).

In spite of the statistical significance, the haematological group differences are not considered as test substance related, while clinical chemical and organ weight changes are attributed to the test substance.

•       Necropsy with gross pathological examination and histopathology:

In 1 mid and 1 high dosed male and in 3 high dosed females focal hepatic necrosis was found, interpreted as a secondary effect, possibly due to a preceding gastrointestinal stress ulcer.

•       Satellite groups: Some statistically significant differences between the control and the high dosed satellite group animals were present at the end of the recovery period, but none of them is attributed to the test substance.