2-methylundecanal

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2000-11-08 to 2000-11-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2000

Report date:

2000

Reference 2

Reference Type:

publication

Title:

QSARS for skin sensitization potential of aldehydes and related compounds

Author:

Patlewicz G, Roberts DW, Walker JD

Year:

2003

Bibliographic source:

QSAR & Combinatorial Science 22 (2):196-203

Report date:

2003

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

(based on draft test guideline)

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

2-methylundecanal

EC Number:

203-765-0

EC Name:

2-methylundecanal

Cas Number:

110-41-8

Molecular formula:

C12H24O

IUPAC Name:

2-methylundecanal

Specific details on test material used for the study:

- Name of test material (as cited in study report): 2-methylundecenal
- Substance type: Slightly viscous clear colourless liquid
- Physical state: Liquid
- Analytical purity: 95% (v/v)
- Impurities (identity and concentrations): No data
- Composition of test material, percentage of components: No data
- Isomers composition: No data
- Purity test date: No data
- Lot/batch No.: No data
- Expiration date of the lot/batch: No date but comment that "Stability was assured by reference to the expiry dates provided by the supplier"
- Stability under test conditions: No data
- Storage condition of test material: Ambient conditions under nitrogen
- Compound Control Sample No: S2352501
- Manufacturer: Sigma

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan UK Ltd
- Age at study initiation: 7-12 wks old
- Weight at study initiation: No data
- Housing: 4 per cage
- Diet: SDS RM1 (E) SQC pelleted diet ad libitum.
- Water: Tap water ad libitum.
- Acclimation period: No data

ENVIRONMENTAL CONDITIONS
- Temperature: 21 ± 3 °C
- Humidity: 50 % ± 20 %
- Air changes (per hr): No data
- Photoperiod: 12 hrs light/2 hrs dark/8 hrs off/2 hrs dimmed in each 24 hr period.

Study design: in vivo (LLNA)

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

0 (control), 0.5, 1.0, 2.5, 5.0 and 10.0 % (w/v).

No. of animals per dose:

4

Details on study design:

TOPICAL APPLICATION
- Each group of mice was treated by topical application with 25µL of the test or control substance to the dorsal surface of each ear for 3 consecutive days.

ADMINISTRATION OF ³HTdR
- 5 days after the first topical application, mice were administered with 20mCi ³HTdR in phosphate buffered saline (PBS) by intravenous tail vein injection with 250µL of 80µCi/mL ³HTdR (78.9µCi/µL ³HTdR following activity confirmation). The tail veins were visualised by placing the mice in a warm air environment for a few minutes.

DETERMINATION OF INCORPORATED ³HTdR
- Approx. 5 hr after ³HTdR injection all mice were sacrificed by CO₂ asphyxiation.
- The draining auricular lymph nodes were rapidly excised and pooled for each experimental group (8 nodes/group) into 1mL of phosphate buffered saline (PBS).
- Single cell suspensions (SCSs) of pooled lymph node cells (LNC) were prepared by gentle mechanical disaggregation of pooled lymph nodes through stainless steel gauze (200 mesh size) using a 5mL ‘B-D discardit’ syringe plunger in a petri dish.
- Approximately 8mL of PBS were subsequently used to wash the mesh and swill the petri dish before each group of pooled LNC SCS was recovered by aspiration, transferred into a centrifuge tube and made up to 10ml with PBS. Pooled LNC were pelleted by centrifugation at 190g (RCF) for 10 mins and the supernatants removed by aspiration before resuspending each LNC pellet with 10mL of PBS. This washing procedure was repeated twice before resuspending each LNC pellet in 3ml of 5% trichloroacetic acid (TCA) for precipitation of macromolecules.
- After incubation with 5 % TCA at 4°C overnight, each precipitate was pelleted and resuspended in 1mL of 5 % TCA. After transferring the precipitates to glass scintillation vials with 10mL of ‘Optiphase mp’ scintillation liquid ³HTdR incorporation was measured on a β-scintillation counter.
- Similarly, background ³HTdR levels were also measured in two 1mL aliquots of 5 % TCA.
- The β-scintillation counter expresses ³HTdR incorporation as the number of radioactive disintegrations per minute (DPM).

INTERPRETATION OF RAW DATA
- The proliferative responses of LNC were expressed as the number of radioactive disintegrations per minute per lymph node (DPM/node) and as the ratio of ³HTdR incorporation into LNC of test lymph nodes relative to that recorded for control lymph nodes (Stimulation Index- SI).
- Before DPM/node values were determined, mean background DPM was subtracted from test and control DPM raw data.

- A test substance was regarded as a sensitiser in the LLNA if the following criteria were fulfilled:
--1. that exposure to at least 1 concentration of the test substance resulted in an incorporation of ³HTdR at least 3-fold or greater than that recorded in the control mice, as indicated by the SI.
--2. that the data were not incompatible with a conventional biological dose response, although allowance would have been made (especially at high topical application concentrations) for either local toxicity or immunological suppression.

Results and discussion

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

EC3

Value:

10

Results 2

Parameter:

SI

Value:

1.4

Test group / Remarks:

concentration 0.5%

Results 3

Parameter:

SI

Value:

1.3

Test group / Remarks:

concentration 1%

Results 4

Parameter:

SI

Value:

1.3

Test group / Remarks:

concentration 2.5%

Results 5

Parameter:

SI

Value:

2.4

Test group / Remarks:

concentration 5%

Results 6

Parameter:

SI

Value:

3

Test group / Remarks:

concentration 10%

Any other information on results incl. tables

2-methylundecanal in AOO elicited a positive lymphocyte response (Stimulation Index (SI) ≥ 3) at 10.0 % which gave a SI of 3.0. The response was negative (SI < 3) at the other concentrations tested (0.5 %, 1.0 %, 2.5 % and 5.0 %). EC3 = 10. There was evidence of a dose response.

Background count - 66 DPM.  DPMs (less background count): 0 % - 3406 dpm, 0.5 % - 4794 dpm, 1.0 % - 4427 dpm, 2.5 % - 4572 dpm, 5.0 % - 8041 dpm, 10.0 % - 10090 dpm

Applicant's summary and conclusion

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Conclusions:

The test substance was assessed for skin sensitisation according to OECD guideline 429. The test material was found to be sensitising to skin at 10 % w/v.