Nα-acetyl-DL-tryptophan

Developmental toxicity / teratogenicity

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

Test material information

Constituent 1

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 / concentrations

Doses / concentrations 1

Dose / conc.:

2 500 mg/kg bw/day (actual dose received)

Remarks:

oral

Doses / concentrations 2

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)

1

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

2

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)

1

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

2

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.