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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
9 February to 13 May 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Fully Guideline- and GLP-compliant

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report Date:
2004

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
GLP compliance:
yes
Type of study:
mouse local lymph node assay (LLNA)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Maleic acid
- CAS No.: 110-16-7
- Physical state: White, cristalline powder
- Lot/batch No.: PUAS 010
- Storage condition of test material: In the dark, may be used under light
- Date of expiry: 30 June 2004

In vivo test system

Test animals

Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Species, strain: Mice, CBA/CaOlaHsd.
- Supplier: Harlan Winkelman GmbH, D-33176 Borchen.
- Sex, specification: Females, healthy young adult nulliparous animals.
- Age of the animals: About 8 weeks at the first administration.
- Weight range of the animals at the first application: 16.9 - 21.2 g.
- Number of animals: 5 animals/group (including spare animals):
15 animals for 3 test substance groups,
5 animals for the negative control group,
5 animals for the positive control group.
- Spare animals: The 5th animal of each group served as spare animal. It was treated in the same way as the other animals of its group.
Since all animals survived and all animals received the correct amount of 3HTdR all spare-animals were taken for the examination of the results.
The number of animals/group was then 5.

ENVIRONMENTAL CONDITIONS
- Hygiene: Optimal hygienic conditions.
- Room temperature: Average of 22.0 °C (continuous monitoring and recording, shortly interrupted due to calibration of the data recorder).
- Relative humidity: Average of 43.0 % (continuous monitoring and recording, shortly interrupted due to calibration of the data recorder).
- Light: Only artificial light from 6.00 a.m. to 6.00 p.m.
- Cages: Single caging. Makrolon cages type II, (22 cm x 16.5 cm ground area, 15 cm high).
- Feed: Altromin maintenance diet for rats and mice, item No. 1324 forte, ad libitum. Random samples of the feed are analysed for contaminants by Altromin, D-32791 Lage.
- Water: Tap water from Makrolon-bottles with stainless steel canules, ad libitum.
- Bedding material: Aspen wood chips, ABEDD Dominik Mayr KEG, A-8580 Köflach.
Germ reduction by autoclaving.
- Acclimatisation: 6 days.

Study design: in vivo (LLNA)

Vehicle:
dimethylformamide
Remarks:
CAS No 68-12-2
Concentration:
Group A (low dose): 1 % (v/v) in DMF
Group B (mid dose): 2.5 % (v/v) in DMF
Group C (high dose): 5 % (w/v) in DMF
No. of animals per dose:
5
Details on study design:
RANGE FINDING TESTS:
A range finding study was performed with two animals/concentration with following concentrations: 47.6%, 25%, 10%, 5%, 2.5 % and 1% (47.6% is the maximal achievable concentration suitable for application, see 2.3.3.). In this study the animals were treated in the same manner as in a main study with 25 µL test substance on the dorsum of each ear on three consecutive days. Ear thickness and body weight were measured on Day 1 before the first administration and on Day 4 about 24 hours after the last administration.
The animals treated with 47.6%, 25% and 10% showed excessive local skin irritation and an increase in ear thickness which was not in the range to be expected from vehicle treated animals of the same strain, sex and age. In the animals treated with 5% no exessive local skin irritation was observed and an abnormal increase in ear thickness was observed in only one animal. The animals dosed with 2.5 and 1 % had whether excessive local skin irritations at the application sites nor an increase in ear thickness in the range finding study.


MAIN STUDY
Bias control
The individual animals were allocated to their groups by random numbers.

Test design
The test substance was administered in 3 concentrations to the dorsal surfaces of the ears of
the animals of the test substance groups. In a manner identical to that of animals in the
treatment groups animals of one negative control group and one positive control group were
treated with DMF and HCA respectively. Each animal was treated for 3 consecutive days.
3 days after the last administration the proliferation of the lymphocytes of the draining lymph
nodes was measured by the determination of the amounts of incorporated 3HTdR.

Incorporation of 3H-methyl thymidine in vivo
5 days after the first topical administration, each animal received 20 µCi 3HTdR by slow
intravenous administration. The injection solution containing nominal 80 µCi/mL 3HTdR was
prepared by the dilution of 720 µL 3HTdR (amersham pharmacia biotech, Kat. Nr.:TRA
310, batch 313, specific activity 2.0 Ci/mmol, radioactive concentration 1 mCi/mL,
radiochemical purity 98.6 %, thymine content 0.2 %) with 8.28 mL PBS. Several minutes
prior to 3HTdR administration the animals were kept restrained in Plexiglas-tubes and the tail
veins were visualised by placing the tails in warm water. Then 250 µL of the injection solution
were intravenously administered to each animal.

Preparation of single cell suspensions and determination of incorporated 3H-methyl thymidine
Approximately 5 hours after 3HTdR injection all animals were sacrificed by carbon dioxide asphyxiation and the draining auricular lymph nodes were rapidly excised. The lymph nodes of each group were pooled in PBS. A single cell suspension (SCS) of lymph node cells (LNC) was prepared by gentle mechanical disaggregation of the pooled lymph nodes through a 70 µm cell strainer. The SCSs were then transferred into centrifuge tubes and LNC were pelleted by centrifugation (4°C, max. 200 g, 10 min). Afterwards supernatants were removed by aspiration. Then the LNC were resuspended and washed twice with PBS. After the final washing the supernatants were removed leaving just a small volume (<0,5 mL) and macromolecules were precipitated by incubation with 5 % trichloroacetic acid (TCA) at 4°C overnight. Each precipitate was pelleted by centrifugation (4 °C, max. 200 g, 10 min) and resuspended in 1 mL TCA. This suspension was transferred into scintillation vials containing 10 mL scintillation cocktail (Packard Bioscience: Ultima Gold, Bestellnr. 6013329) and 3HTdR incorporation was determined with a beta-scintillation counter (TriCarb 2200CA, Packard Instrument Co., protocol 4: single label 3H, dpm, AEC-quenchcurve in Ultima Gold from 21 June 2002).
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
Analysis of variance followed by the Scheffé-test: all data with means and standard deviations determined, comparisons between dosed groups and the negative control group (used for ear thickness)
t-test: all data with means and standard deviations determined, for comparison of two groups only (used for ear thickness).
P = 0.05 was chosen in each test. Two tailed tests were used.

Results and discussion

Positive control results:
Moderate erythema was noted in all animals of the positive control group on Days 2-5.
Application of 25% HCA in AOO resulted in an SI of 14.6.
This result proves the sensitivity of the strain of animals used and the reliability of the experimental technique.

In vivo (LLNA)

Resultsopen allclose all
Parameter:
SI
Remarks on result:
other: see Remark
Remarks:
The calculated stimulation indices (test substance/negative control ratio) were decisive for the grading of the potential of sensitisation: According to the guidelines the decision process with regard to a positive response includes a stimulation index of equal to or greater than 3, together with consideration of dose-response. group K (negative control): 1 group A (low dose): 11.2 group B (mid dose): 22.0 group C (high dose): 31.5 group P (positive control): 14.6
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: group K (negative control): 3029 group A (low dose): 34064 group B (mid dose): 66621 group C (high dose): 95432 group P (positive control): 44372

Applicant's summary and conclusion

Interpretation of results:
sensitising
Remarks:
Migrated information
Conclusions:
"Maleic acid" is regarded as a sensitiser in the LLNA according to the OECD-Guideline 429, "Skin Sensitisation: Local Lymph Node Assay", since the SIs of all examined test substance concentrations were clearly greater than 3.

According to the results of this study and to the Directive 2001/59/EC for classification, the test substance "Maleic acid" needs to be labelled with "R43 May cause sensitisation by skin contact".
Executive summary:

Aim

The Local Lymph Node Assay was performed to evaluate a possible skin sensitising potential of "Maleic acid" according to the OECD-Guideline 429, 24 April 2002.

 

Method

 

The test substance was used solved in N,N-Dimethylformamid (DMF)and was administered to three groups of 5 female CBA/Ca mice. Administration was performed epicutaneously to the dorsal surface of both ears, once a day on three consecutive days. The volume administered was 25 µL per ear.

 

Concentrations used:

·      Group A (low dose):               1% (v/v) solution of "Maleic acid" in DMF

·      Group B (mid dose):            2.5% (v/v) solution of "Maleic acid" in DMF

·      Group C (high dose):              5% (w/v )solution of "Maleic acid" in DMF

 

Two groups with 5 animals each served as positive and negative controls. Both control substances were administered under identical conditions as the test substances.

The following solutions served as control substances:

·        Group P (positive control):     25% (v/v) solution of hexyl cinnamic aldehyde in acetone:olive oil (4:1, v/v)

·        Group K (negative control):    DMF

 

5 days after the first topical application,3H-thymidine was intravenously administered to all mice via a tail vein. Approximately 5 hours later all animals were sacrificed, the draining auricular lymph nodes were excised, pooled for each group, and single cell suspensions were prepared. Then incorporation of3H-methyl thymidine into the cells was determined (liquid scintillation counter) and compared with the negative controls. The stimulation index (SI) was calculated as the ratio of the disintegrations per minute (dpm) of the dosed groups or of the positive control group to the dpm of the negative control group.

Ear thickness of all animals was measured before the first and 24 hours after the last administration to get an information about the skin irritating properties of the substance administered.

Results

 

General

All animals survived till the end of the study.

Body mass and body mass gain was in the range to be expected from animals of the same strain, sex and age.

No skin irritating effects were observed in the negative control group.

Moderate erythema were noted in all animals of the positive control group on Days 2-5, in all animals of group C on Day 2, and in few animals of the groups A, B and C on Day 3 indicating local skin irritation. This irritating effect was confirmed by a statistically significant difference of the mean ear thickness differences of the negative control group versus the test substance groups B and C and the positive control group. There was no statistically significant difference of the mean ear thickness differences between the negative control group and the test substance group A.

Different other effects (e.g. lesions, white crusts) were observed in some animals of the test substance groups throughout the whole study. The observed lesions were not dose related and were partially unilateral. They are attributed to scratching because of a test substance induced itching and not to excessive skin irritation.

 

3H-thymidine incorporation, stimulation indices

The calculated stimulation indices (test substance/negative control ratio) were decisive for the grading of the potential of sensitisation: According to the guideline the decision process with regard to a positive response includes a stimulation index of equal to or greater than 3, together with consideration of dose-response.

 

The SIs of the tested test substance concentrations were 11.2 (low dose), 22.0 (mid dose) and 31.5 (high dose).

 

Positive control

The positive control substance led to a stimulation index of 14.6, thus demonstrating the validity of the experiment.

 

Conclusion

According to the OECD-Guideline 429, "Skin Sensitisation: Local Lymph Node Assay", "Maleic acid" is regarded as a sensitiser in the LLNA.

 

According to the results of this study and to the Directive 2001/59/EC for classification, the test substance "Maleic acid " needs to be labelled with " R43 May cause sensitisation by skin contact".