2-(4-aminophenyl)butanoic acid

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-01-16 to 2018-01-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Version / remarks:

2010

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

2-(4-Aminophenyl)butanoic acid

Cas Number:

29644-97-1

Molecular formula:

C10-H13-N-O2

IUPAC Name:

2-(4-Aminophenyl)butanoic acid

Specific details on test material used for the study:

Batch No.: 17006R72A
Purity: 12.5 wv% ± 3% in water

In vivo test system

Test animals

Species:

mouse

Strain:

CBA:J

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Janvier, Le Genest-Saint-Isle, France
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation: Young adult animals (approximately 10 weeks old)
- Weight at study initiation: 19.7 to 23.1 g
- Housing: On arrival and following assignment to the study, animals were group housed (up to 5 animals of the same sex and same dosing group together) in polycarbonate cages containing sterilized sawdust as bedding equipped with water bottles. Animals were separated during designated procedures/activities. Each cage was clearly labeled.
- Diet (e.g. ad libitum): Pelleted rodent diet was provided ad libitum throughout the study, except during designated procedures.
- Water (e.g. ad libitum): Municipal tap-water was freely available to each animal via water bottles.
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Target temperatures is 18 to 24°C, the actual is 21 to 22°C
- Humidity: Relative target humidity is 40 to 70%, the actucal is 42 to 46%
- Air changes (per hr): Ten or greater air changes per hour with 100% fresh air
- Photoperiod (hrs dark / hrs light): 12-hour light/12-hour dark cycle

Study design: in vivo (LLNA)

Vehicle:

dimethylformamide

Concentration:

Pre-screen Test: 50 and 100% (w/w)
Main Test: 0, 10, 25 and 50 % (w/w)

No. of animals per dose:

Pre-screen Test: two animals
Main Test: five animals

Details on study design:

PRE-SCREEN TESTS:
A pre-screen test was conducted in order to select the highest test item concentration to be used in the main study. In principle, this highest concentration should cause no systemic
toxicity, may give well-defined irritation as the most pronounced response (maximum grade 2 and/or an increase in ear thickness < 25%) and/or is the highest possible concentration that can technically be applied.
Two test item concentrations were tested; a 50% and 100% concentration. The highest
concentration was the highest concentration as required by the guidelines.
The test system, procedures and techniques were identical to those used in the main study
except that the test item formulation at 50% was not stirred for a short period of time on Day 3 and that the assessment of lymph node proliferation and necropsy were not performed. Two young adult animals per concentration were selected. Each animal was treated with one concentration on three consecutive days. Animals were group housed in labeled Makrolon cages (MII type, height 14 cm). Ear thickness measurements were conducted using a digital thickness gauge (Kroeplin C110T-K) prior to dosing on Days 1 and 3, and on Day 6.
Animals were sacrificed after the final observation.

MAIN STUDY:Three groups of five animals were treated with one test item concentration per group. The highest test item concentration was selected from the pre-screen test. One group of five animals was treated with the vehicle.
- Allocation/concetration: 0, 10, 25 and 50%
- Induction - Days 1, 2 and 3: The dorsal surface of both ears was topically treated (25 mL/ear with the test item, at approximately the same time on each day. The concentrations were stirred with a magnetic stirrer immediately prior to dosing. The control animals were treated in the same way as the experimental animals, except that the vehicle was administered instead of the test item.
- Excision of the Nodes - Day 6: Each animal was injected via the tail vein with 0.25 mL of sterile phosphate buffered saline (PBS) containing 20 mCi of 3H-methyl thymidine.
After five hours, all animals were killed by intraperitoneal injection (0.2 mL/animal) of
Euthasol® 20%. The draining (auricular) lymph node of each ear was excised. The relative size of the nodes (as compared to normal) was estimated by visual examination and abnormalities of the nodes and surrounding area were recorded. The nodes were pooled for each animal in PBS.
-Tissue Processing for Radioactivity - Day 6: Following excision of the nodes, a single cell suspension of lymph node cells (LNC) was prepared in PBS by gentle separation through stainless steel gauze (maze size: 200 μm, diameter: ± 1.5 cm). LNC were washed twice with an excess of PBS by centrifugation at 200g for 10 minutes at 4ºC. To precipitate the DNA, the LNC were exposed to 5% trichloroacetic acid (TCA) and then stored in the refrigerator until the next day.
- Radioactivity Measurements - Day 7: Precipitates were recovered by centrifugation, resuspended in 1 mL TCA and transferred to 10 mL of Ultima Gold cocktail as the scintillation fluid. Radioactivity measurements were performed using a Packard scintillation counter (2800TR). Counting time was to a statistical precision of ± 0.2% or a maximum of 5 minutes whichever came first. The scintillation counter was programmed to automatically subtract background and convert Counts Per Minute (CPM) to Disintegrations Per Minute (DPM).

Results and discussion

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Value:

1.2

Test group / Remarks:

the test item concentrations 10%

Results 2

Key result

Parameter:

SI

Value:

1

Test group / Remarks:

the test item concentrations 25 %

Results 3

Key result

Parameter:

SI

Value:

0.8

Test group / Remarks:

the test item concentrations 50 %

Any other information on results incl. tables

- Skin Reactions / Irritation: No irritation was observed in any of the animals.

- Systemic Toxicity: No mortality occurred and no clinical signs of systemic toxicity were observed in the animals of the main study. Body weights and body weight gain of experimental animals remained in the same range as controls over the study period. The body weight loss noted for some animals across the dose groups was considered not toxicologically significant since the changes were slight in nature and no concentration-related incidence was apparent.

- Macroscopic Examination of the Lymph Nodes and Surrounding Area: All auricular lymph nodes of the animals of the experimental and control groups were considered normal in size. No macroscopic abnormalities of the surrounding area were noted for any of the animals.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Since there was no indication that the test item elicits a SI >=3 when tested up to 50%, test item was not considered to be a skin sensitizer. It was established that the EC3 value (the estimated test item concentration that will give a SI =3) (if any) exceeds 50%.
Based on these results, the test item would not be regarded as a skin sensitizer according to the recommendations made in the test guidelines.

Executive summary:

The objective of this study was to evaluate whether the test item induces skin sensitization in mice (Local Lymph Node Assay) after three epidermal exposures of the animals according to OECD 429.

 

In the main study, three experimental groups of five female CBA/J mice were treated with test item concentrations of 10, 25 or 50% w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with the vehicle alone (N, N-dimethylformamide (DMF)). Three days after the last exposure, all animals were injected with 3H-methyl thymidine and after five hours the draining (auricular) lymph nodes were excised and pooled for each animal. After precipitating the DNA of the lymph node cells, radioactivity measurements were performed. The activity was expressed as the number of disintegrations per minute (DPM) and a stimulation index (SI) was subsequently calculated for each group.

 

No irritation was observed in any of the animals.

 

No mortality occurred and no clinical signs of systemic toxicity were observed in the animals of the main study. Body weights and body weight gain of experimental animals remained in the same range as controls over the study period. The body weight loss noted for some animals across the dose groups was considered not toxicologically significant since the changes were slight in nature and no concentration-related incidence was apparent.

 

All auricular lymph nodes of the animals of the experimental and control groups were considered normal in size. No macroscopic abnormalities of the surrounding area were noted for any of the animals.

 

Mean DPM/animal values for the experimental groups treated with test item concentrations 10, 25 and 50% were 777, 635 and 511 DPM, respectively. The mean DPM/animal value for the vehicle control group was 626 DPM. The SI values calculated for the test item concentrations 10, 25 and 50% were 1.2, 1.0 and 0.8, respectively.

 

Since there was no indication that the test item elicits a SI >=3 when tested up to 50%, the test item was not considered to be a skin sensitizer. It was established that the EC3 value (the estimated test item concentration that will give a SI =3) (if any) exceeds 50%.

 

Based on these results, the test item would not be regarded as a skin sensitizer according to the recommendations made in the test guidelines.