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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
no guideline followed
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1980
Report date:
1980

Materials and methods

Principles of method if other than guideline:
- Short description of test conditions: The developmental toxicity study of N-acetyl-L-tryptophan was conducted in Wistar rats. N-acetyl-L-tryptophan was administered orally at doses of 2.5 and 5.0 g/kg bw/day from GD 7 to 17. All dams were autopsied for the assessment of fetal development parameters on GD 20.
GLP compliance:
no
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
N-acetyl-L-tryptophan
EC Number:
214-935-9
EC Name:
N-acetyl-L-tryptophan
Cas Number:
1218-34-4
Molecular formula:
C13H14N2O3
IUPAC Name:
N-acetyl-L-tryptophan
Test material form:
solid

Test animals

Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: KITAYAMA LABES CO.,LTD., Ina-city, Japan
- Age at study initiation: 11 weeks
- Diet: MF except for gestation and lactation period and NMF for gestation and lactation period, purchased by Oriental Yeast Co., Ltd, Japan, were given ad libitum
- Water: tap water, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2
- Humidity (%): 55 ± 5

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
VEHICLE
- Justification for use and choice of vehicle (if other than water): due to the low water solubility, CMC was used as vehicle
- Concentration in vehicle: 1%
Analytical verification of doses or concentrations:
no
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
Duration of treatment / exposure:
females: 11 days; (from Day 7 to 17 of gestation (GD))
Frequency of treatment:
daily
Duration of test:
GD 7 - 20
Doses / concentrationsopen allclose all
Dose / conc.:
2 500 mg/kg bw/day (actual dose received)
Remarks:
oral
Dose / conc.:
5 000 mg/kg bw/day (actual dose received)
Remarks:
oral
No. of animals per sex per dose:
21, 22 and 20 dams (control, 2500, 5000 mg/kg bw/day)
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Since the LD50 value was 15000 mg/kg bw/day for oral administration, 5000 mg/kg bw/day was applied as the highest dose.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: every second day

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: every second day

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on Day 20 of gestation
- Organs examined: brain, pituitary, thymus, heart, lungs, liver, kidneys, spleen, adrenals, ovaries

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on Day 20 of gestation
- Anaesthetic used for blood collection: Yes, chloroform
- How many animals: 21 in control, 22 in 2500, and 20 in 5000 mg/kg bw/day
- Parameters checked: red blood cell count (RBC), white blood cell count (WBC), hemoglobin, hematocrit, platelet

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on Day 20 of gestation
- How many animals: 21 in control, 22 in 2500, and 20 in 5000 mg/kg bw/day
- Parameters checked: total protein, A/G, urea N, glucose, GOT (glutamate oxaloacetate transaminase), and GPT (glutamate pyruvate transaminase)
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: No
- Number of implantations: Yes
- Number of early resorptions: No
- Number of late resorptions: No
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: No
- Skeletal examinations: Yes: all per litter
- Head examinations: No
Statistics:
Wilcoxon test for % of fetal death, the number of abnormal fetus, the number of live offsprings, % of malformation, % of anomaly, effects on development of offspring, and the number of variation and ossification except for ossified calnei and ossified tail.
Chi-squared test for copulation index, fertility index, delivery index, rearing index, sex ratio of fetus and offspring.
t test for the rest items.
Indices:
copulation index, fertility index, delivery index, rearing index, sex ratio

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
no effects observed
Dermal irritation (if dermal study):
not examined
Mortality:
mortality observed, non-treatment-related
Description (incidence):
One dam of the 5000 mg/kg bw/day dose group died caused by pneumonia. This is considered to be an incidental occurrence.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
The body weight gain during gestation was significantly decreased (35%) in the 5000 mg/kg bw/day group compared with the control group. The body weight gain in the 2500 mg/kg bw/day group was reduced by 9% compared with the control group; this change was not significant.
Food consumption and compound intake (if feeding study):
effects observed, non-treatment-related
Description (incidence and severity):
Food consumption was significantly decreased in the 2500 and 5000 mg/kg bw/day dose groups compared with the control group (9 and 15%, respectively).
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, non-treatment-related
Description (incidence and severity):
Water consumption was significantly increased in the 5000 mg/kg bw/day group. This is considered to be an incidental occurrence as no effects were seen on the kidneys.
Ophthalmological findings:
not examined
Haematological findings:
effects observed, non-treatment-related
Description (incidence and severity):
The leucocyte level was significantly increased in the 5000 mg/kg bw/day group. As no relevant hematological or histopathological effects were observed, this is not considered to be a treatment-related effect.
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:
effects observed, non-treatment-related
Description (incidence and severity):
The absolute weight of thymus was significantly decreased in the 5000 mg/kg bw/day group. As no relevant effects were observed on the relative organ weight or during gross pathology examination, this is not considered to be a treatment-related effect.
Gross pathological findings:
no effects observed
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed

Maternal developmental toxicity

Number of abortions:
not examined
Pre- and post-implantation loss:
not examined
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
effects observed, treatment-related
Description (incidence and severity):
Fetal death was significantly increased in the 5000 mg/kg bw/day group. This is considered to be related to maternal toxicity observed at this dose level.
Changes in pregnancy duration:
not examined
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not examined
Changes in number of pregnant:
no effects observed
Other effects:
no effects observed

Effect levels (maternal animals)

open allclose all
Key result
Dose descriptor:
NOAEL
Remarks:
systemic
Effect level:
2 500 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
body weight and weight gain
Remarks on result:
other: reduced body weight gain observed at 5000 mg/kg bw/day
Key result
Dose descriptor:
NOAEL
Remarks:
fertility
Effect level:
5 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: no treatment-related adverse effects observed up and including to the highest dose level

Maternal abnormalities

Key result
Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
The fetal weight of female offspring was significantly decreased in the 5000 mg/kg bw/day group. This is considered to be a secondary effect caused by the reduced weight gain observed in the dams.


Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): not examined
Reduction in number of live offspring:
not examined
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
not examined
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The incidence of bipartite, asymmetrical sternebrae was significantly increased in the treatment groups, compared with the control group. Poorly ossified sternebrae was also significantly increased in the 5000 mg/kg bw/day group, compared with the control group. The variation (in bipartite, asymmetrical sternebrae) was minimal and the delay in ossification was very slight; the high value observed in the control group indicates that the structure was developing rapidly at the time of the Cesarean section. This means that some animals had already completed the fusion of the sternebral ossification centres, while others had not, and that a relatively small difference in the time point of examination will result in different values. Therefore, the changes are not considered to be treatment-related effects, but an incidental finding.
The ossification of the caudal vertebrae was significantly increased in the treated groups, compared with the control group (see Table 3 under 'Any other information on results incl tables'. The difference was minimal (< 15%) and has no developmental relevance and is therefore considered to be incidental.
Visceral malformations:
no effects observed
Other effects:
no effects observed
Details on embryotoxic / teratogenic effects:
After oral administration of 5000 mg/kg bw/day, an increase in mortality and a decrease in body weight gain were noted in fetuses. These effects are considered to be secondary effects casued by the maternal toxicity observed at his dose level (decreased body weight gain and food consumption).

Effect levels (fetuses)

open allclose all
Key result
Dose descriptor:
NOAEL
Effect level:
2 500 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
reduction in number of live offspring
fetal/pup body weight changes
Remarks on result:
other: effect noted only at level of maternal systemic toxicity and at a dose considerably higher than the limit dose recommended in the OECD guideline 414
Key result
Dose descriptor:
LOAEL
Effect level:
5 000 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
reduction in number of live offspring
fetal/pup body weight changes
Remarks on result:
other: effect noted only at level of maternal systemic toxicity and at a dose considerably higher than the limit dose recommended in the OECD guideline 414

Fetal abnormalities

Key result
Abnormalities:
no effects observed

Overall developmental toxicity

Key result
Developmental effects observed:
no

Any other information on results incl. tables

Table 1. Effect of N-acetyl-L-Tryptophan on pregnant females treated orally on days 7 to 17 of gestation

 

Control

N-acetyl-L-tryptophan (g/kg)

2.5

5.0

No. of pregnant females

21

22

20

Maternal death

0

0

1

Body weight gain during gestation

(g ± S.D.)

124 ± 24

114 ± 14

79 ± 36**

Food consumption during gestation (g/100g ± S.D.)

145 ± 11

133 ± 9**

124 ± 12**

Organ weight

Thymus

 (g ± S.D.)

0.26 ± 0.07

0.20 ± 0.07

0.18 ± 0.08**

Hematological findings

Erythrocytes

(10000/mm3 ± S.D.)

96 ± 23

103 ± 29

115 ± 32*

*:        significantly different from control at P≤0.05

**:      significantly different from control at P≤0.01

 

Table 2. Effect of N-acetyl-L-Tryptophan on fetus from pregnant females treated orally on days 7 to 17 of gestation

 

Control

N-acetyl-L-tryptophan (g/kg)

2.5

5.0

No. of pregnant females

21

22

19

% Fetal death (Mean ± S.D.)

5.3 ± 14.2

3.9 ± 6.8

19.5 ± 30.9**

Fetal weight

Female

(g ± S.D.)

3.81 ± 0.23

3.71 ± 0.31

3.53 ± 0.45*

*:        significantly different from control at P≤0.05

**:      significantly different from control at P≤0.01

 

 

Table 3. Effect of N-acetyl-L-Tryptophan on visceral and skeletal development of fetus from pregnant females treated orally on days 7 to 17 of gestation

 

Control

N-acetyl-L-tryptophan (g/kg)

2.5

5.0

No. of litters

21

22

17

Skeletal observation

No. of fetus examined

171

186

131

Variation

Bipartite, asymmetrical sternebrae

17.9 (33)

28.0 (51)*

35.7 (47)**

Poorly ossified sternebrae

15.9 (29)

23.0 (43)

43.6 (58)*

Ossification

Caudal vertebrae

4.2 ± 0.3

3.8 ± 0.3**

3.6 ± 0.8*


*:        significantly different from control at P≤0.05

**:      significantly different from control at P≤0.01

Applicant's summary and conclusion

Conclusions:
The effects in the offspring were noted only at level of maternal systemic toxicity, therefore the test substance is considered to have no effect on effect on intrauterine development, thus the highest dose level of 5000 mg/kg bw/day was considered as a NOAEL for fertility, and 2500 mg/kg bw/day was considered as a NOAEL for developmental effects.