6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-propionaldehyde

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

The study was conducted between 15 June 2009 and 14 July 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Historical in vivo previously available before new regulation requirements came into force

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-propionaldehyde

EC Number:

251-717-2

EC Name:

6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-propionaldehyde

Cas Number:

33885-51-7

Molecular formula:

C12H18O

IUPAC Name:

3-(6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl)propanal

Test material form:

liquid

In vivo test system

Test animals

Species:

mouse

Strain:

other: CBA/J

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Jackson Laboratories, Bar Harbor, ME 04609
- Age at study initiation: 8 weeks
- Weight at study initiation: 19 to 23 g
- Housing: 5 animals/cage (randomly allocated)
- Diet (e.g. ad libitum): ad libitum (Harlan Teklad Certified Rodent Chow 7012C)
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-21
- Humidity (%): 44-62
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (LLNA)

Vehicle:

other: Ethanol/diethyl phthalate 1:3

Concentration:

2.5 %, 5%, 10%, 25% or 50% v/v in EtOH/DEP 1:3

No. of animals per dose:

5

Details on study design:

MAIN STUDY

Test Item Administration
Groups of five mice were treated with the test item at concentrations of 2.5 %, 5%, 10%, 25% or 50% v/v in EtOH/DEP. No justification on the choice of vehicle is provided. The doses were chosen on the basis of avoiding systemic toxicity and overtly induced skin irritation, according to reported uses of the test material. The mice were treated by daily application of 25 µl of the appropriate concentration of the test item to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The test item formulation was administered using an automatic micropipette and spread over the dorsal surface of the ear using the tip of the pipette.
A further group of five mice received the vehicle alone in the same manner.
The positive control animals were similarly treated to the test animals except that 25 µl of the positive control item, α Hexylcinnamaldehyde, at a concentration of 5%, 15% and 35% v/v in ethanol/diethyl phthalate 1:3 was applied to the dorsal surface of each ear.

3H-Methyl Thymidine Administration
On day 6, all mice were injected via the tail vein with 250 µl of phosphate buffered saline (PBS) containing 3H methyl thymidine (3HTdR:80µCi/ml, specific activity 2.0 Ci/mmol, ARC UK Ltd) giving a total of 20 µCi to each mouse.

Observations
Clinical Observations: All animals were observed before and after dosing, and on a daily basis on Days 4, 5 and 6. Any signs of toxicity or signs of ill health during the test were recorded. The animals were also examined daily for erythema and edema on the site of application.

Bodyweights: The bodyweight of each mouse was recorded on Day 1 (prior to dosing) and Day 6 (prior to termination).

Terminal Procedures
Termination: Five hours following the administration of 3HTdR all mice were killed by carbon dioxide asphyxiation. For each individual animal of each group the draining auricular lymph nodes were excised and processed.

Preparation of Single Cell Suspension: A single cell suspension of the lymph node cells for each individual animal was prepared. The lymph node cells were rinsed with PBS and precipitated with 5% trichloroacetic acid during night. The lymph node cells suspension was transferred to a centrifuge tube and thereafter, the pellets were resuspended in 1 ml TCA and transferred to scintillation fluid vials for the measurement of the radioactive material.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

Data was processed to give group mean values for disintegrations per minute and standard deviations where appropriate. Increases in the radioactivity compared to the vehicle control were recorded. Individual DPM values were analyzed with log values. Dunett's test was used to determine significance when required. The EC3 was calculated as follows:

EC3=c+[(3-d)/(b-d)](a-c),

data points between the SI=3 lie in the coordinates (a,b) and (c,d)

Results and discussion

Positive control results:

The positive control item, α-Hexylcinnamaldehyde, gave a Stimulation Index of greater than 3 when tested at a concentration of 25 % v/v.

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

EC3

Value:

25

Results 2

Parameter:

SI

Value:

1.8

Remarks on result:

other: 2.5%

Results 3

Parameter:

SI

Value:

1.1

Remarks on result:

other: 5%

Results 4

Parameter:

SI

Value:

1.7

Remarks on result:

other: 10%

Results 5

Parameter:

SI

Value:

3

Remarks on result:

other: 25%

Results 6

Parameter:

SI

Value:

4.5

Remarks on result:

other: 50%

Cellular proliferation data / Observations:

No erythema or edema was noted. There were no deaths. No signs of systemic toxicity were noted in the test or control animals during the test. Bodyweight changes of the test animals between Day 1 and Day 6 were comparable to those observed in the corresponding control group animals over the same period.

Applicant's summary and conclusion

Interpretation of results:

other: Substance is a skin sensitiser (1B)

Remarks:

in accordance with EU CLP (1272/2008 and its amendments)

Conclusions:

The test item was considered to be a sensitiser under the conditions of the test and resulted in an EC3 value of 25%.

Executive summary:

The skin sensitisation potential of the test substance has been tested according to OECD TG 429 (Local Lymph Node Assay). At 2.5, 5, 10, 25 and 50% the substance showed SI values of 1.8, 1.1, 1.7, 3.0 and 4.5, respectively. An EC3 value of 25% was derived. The substance was found to be a skin sensitiser under the conditions of this test.