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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Conducted according to OECD 402, in full comformance with GLP.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
yes
Remarks:
The relative humidity in the animal room was between approximately 21 - 65 % for few hours, due to maintenance. This deviation to the study plan, however, does not affect the validity of the study.
GLP compliance:
yes (incl. certificate)
Type of study:
mouse local lymph node assay (LLNA)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Internal Test Item Number: S 1046911
The test item and the information concerning the test item were provided by the sponsor.
Identity: Tert-Butyl peroxybenzoate
Cas No.: 614-45-9
Batch No.: 0903225181
Purity: 99.2 %
Stability in solvent: Not indicated by the sponsor
Storage: In the refrigerator at +2 to + 8 °C
Expiration Date: April 01, 2010

In vivo test system

Test animals

Species:
mouse
Strain:
other: CBA/CaOlaHsd
Sex:
female
Details on test animals and environmental conditions:
Test system Mice, CBA/CaOlaHsd
Rationale Recognised as the recommended test system
Source Harlan Laboratories B.V.
Postbus 6174
5960 AD Horst / The Netherlands
Number of animals for
the pre-test 2 females
Number of animals for
the main study
20 females
Number of animals per group 5 females (nulliparous and non-pregnant)
Number of test groups 3
Number of control (vehicle) groups 1
Age 8 - 12 weeks (beginning of treatment)
Body weight 18.9-23 g
Identification Single caging. The animals were distributed into the test groups at random and identified by cage number.
Acclimatisation At least 5 days prior to the start of dosing under test conditions after health examination. Only animals without any visible signs of illness were used for the study.

The animals were kept conventionally. The experiment was conducted under standard laboratory conditions.
Housing: single
Cage Type: Makrolon Type II, with wire mesh top
(EHRET GmbH, 79302 Emmendingen, Germany)
Bedding: granulated soft wood bedding
(Rettenmaier & Söhne GmbH + Co. KG, 73494 Rosenberg, Germany)
Feed: pelleted standard diet, ad libitum
(Harlan Laboratories B.V., 5960 AD Horst / Netherlands)
Water: tap water, ad libitum,
(Gemeindewerke, 64380 Rossdorf, Germany)
Environment: temperature 22 + 2°C
relative humidity 21-65%
artificial light 6.00 a.m. - 6.00 p.m.

Study design: in vivo (LLNA)

Vehicle:
dimethylformamide
Concentration:
0, 25%, 50%, & 100%
No. of animals per dose:
5
Details on study design:
4.3 Experimental Design and Procedures
4.3.1 Topical Application
Each test group of mice was treated by topical (epidermal) application to the dorsal surface of each ear lobe (left and right) with different test item concentrations of 25, 50, and 100% (w/v) in dimethylformamide. The application volume, 25 µl, was spread over the entire dorsal surface (  8 mm) of each ear lobe once daily for three consecutive days. A further group of mice was treated with an equivalent volume of the relevant vehicle alone (control animals).
4.3.2 Administration of 3H-Methyl Thymidine
3H-methyl thymidine (3HTdR) was purchased from GE Healthcare (GE Healthcare product code no. TRA 310; specific activity, 2 Ci/mmol; concentration, 1 mCi/ml).
Five days after the first topical application, all mice were administered with 250 µl of 80.7 µCi/ml 3HTdR (corresponds to 20.2 µCi 3HTdR per mouse) by intravenous injection via a tail vein.
4.3.3 Determination of Incorporated 3HTdR
Approximately five hours after treatment with 3HTdR all mice were euthanised by intraperitoneal injection of Pentobarbital-Natrium (Release, WDT, D-30827 Garbsen).
The draining lymph nodes were rapidly excised and pooled per group (8 nodes per group). Single cell suspensions (in phosphate buffered saline) of pooled lymph node cells were prepared by gentle mechanical disaggregation through stainless steel gauze (200 µm mesh size). After washing two times with phosphate buffered saline (approx. 10 ml) the lymph node cells were resuspended in 5 % trichloroacetic acid (approx. 3 ml) and incubated at approximately +4 °C for at least 18 hours for precipitation of macromolecules. The precipitates were then resuspended in 5 % trichloroacetic acid (1 ml) and transferred to plastic scintillation vials with 10 ml of ‘Ultima Gold’ scintillation liquid (Perkin Elmer (LAS) GmbH, D-63110 Rodgau) and thoroughly mixed.
The level of 3HTdR incorporation was then measured on a -scintillation counter (Tricarb 2900 TR, Perkin Elmer (LAS) GmbH, D-63110 Rodgau). Similarly, background 3HTdR levels were also measured in two 1ml-aliquots of 5 % trichloroacetic acid. The -scintillation counter expresses 3HTdR incorporation as the number of radioactive disintegrations per minute (DPM).

Results and discussion

In vivo (LLNA)

Resultsopen allclose all
Key result
Parameter:
SI
Value:
20.04
Test group / Remarks:
In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.
Key result
Parameter:
SI
Value:
28.16
Test group / Remarks:
In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.
Key result
Parameter:
SI
Value:
32.77
Test group / Remarks:
In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.

Applicant's summary and conclusion

Interpretation of results:
sensitising
Conclusions:
The test item tert-Butyl peroxybenzoate was found to be a skin sensitiser under the described conditions.
Executive summary:

In the study the test item tert-Butyl peroxybenzoate dissolved in dimethylformamide was assessed for its possible contact allergenic potential.

For this purpose a local lymph node assay was performed using test item concentrations of 25, 50, and 100%.

The animals did not show any signs of systemic toxicity during the course of the study and cases of mortality were not observed. 24 after the first and second application and 1 hour after the second and third application all animal of the mid dose (50%) showed slight redness of the ear skin and all animals of the high dose (100%) showed swollen ears. All animals of the high dose (100%) also showed slight redness of the ear skin 24 hours after the second and 1 hour after the third application. However, these local signs of irritation resolved until the day of preparation (day 6). Animals treated with a concentration of 25% did not show any local signs of irritation during the course of the study.

In this study Stimulation Indices (S.I.) of 20.04, 28.16, and 32.77 were determined with the test item at concentrations of 25, 50, and 100% in dimethylformamide, respectively.

The test item tert-Butyl peroxybenzoate was found to be a skin sensitiser.