2-phenylpropionaldehyde-dimethyl acetal

Skin sensitisation

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

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:

1,1-dimethoxy-2-phenylethane

EC Number:

202-945-6

EC Name:

1,1-dimethoxy-2-phenylethane

Cas Number:

101-48-4

Molecular formula:

C10H14O2

IUPAC Name:

(2,2-dimethoxyethyl)benzene

Test material form:

liquid

In vivo test system

Test animals

Species:

mouse

Strain:

other: CBA/Jcr

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Sprague-Dawley; Indianapolis, IN
- Females nulliparous and non-pregnant: yes
- Age at study initiation: 11 - 12 weeks
- Weight at study initiation: 21.3 - 24.6g
- Housing: 1-5 per cage in polycarbonate box with bedding
- Diet: PMI Feeds Inc. Formulab #5008, ad libitum
- Water: Municipal water supply, ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 - 23
- Humidity (%): 48 - 97
- Air changes (per hr): at least 10
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (LLNA)

Vehicle:

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

Concentration:

25, 50, and 100%

No. of animals per dose:

5

Details on study design:

PRE-SCREEN TESTS:
No range-finding test was conducted

MAIN STUDY
On days 1, 2, and 3, each test animal in its group received an open application of 2.5 µL test substance (at appropriate dilution in vehicle or neat) to the dorsum of both ears. The vehicle group was treated similarly, but with the vehicle alone. On day 6, all test and control animals were injected in the tail vein with 250 µL of 0.01 M phosphate-buffered saline (PBS), pH 7.4, at 25°C containing 20 µCi of [methyl-3H] Thymidine. Five hours after injection, animals were sacrificed with an overdose of CO2, the draining auricular lymph nodes excised and pairs from each individual animal processed.
A single cell suspension was prepared by gentle mechanical disintegration through 200 mesh stainless steel gauze. Cells were washed twice with an excess of PBS and precipitated with 5% trichloroacetic acid (TCA) at 4°C for 18 hours. The pellets were resuspended in 1 mL of TCA and transferred to 10 mL of scintillation fluid. Incorporation of tritiated thymidine was measured by liquid scintillation counting as disintegrations per minute (DPM) from paired lymph nodes of each animal, and mean DPM/animal was calculated for each group. Background DPM values, determined by blanks were automatically subtracted by the scintillation counter.

BODY WEIGHTS AND OBSERVATIONS
Individual body weights were recorded on Day 1 prior to dosing, and Day 6, prior to injection. All test and control animals were observed daily for clinical signs of toxicity and any excessive irritation at the test site.

Positive control substance(s):

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

Statistics:

A one-way parametric analysis of variance (ANOVA) with Dunnett's Multiple Comparisons Test, using GraphPad InStat version 3.06, was performed on DPM counts. If test groups showed a SI >3, then an extrapolated EC3 value was calculated from SI values at low% and either mid or high% concentrations.

Results and discussion

Positive control results:

The mean DPM was 9030 resulting in a SI of 13.3.

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Value:

2.97

Remarks on result:

other: 25%

Results 2

Parameter:

SI

Value:

1.84

Remarks on result:

other: 50%

Results 3

Parameter:

SI

Value:

2.39

Remarks on result:

other: 100%

Cellular proliferation data / Observations:

CELLULAR PROLIFERATION DATA: Treatment with the test substance at concentrations of 0, 25, 50, and 100% resulted in average DPM values of 681, 2020, 1252 and 1629, respectively. See table 1 for details.

CLINICAL OBSERVATIONS: All test and vehicle animals appeared normal for the duration of the study. One animal of the positive control group exhibited activity decrease on Day 6.

BODY WEIGHTS: All test groups animals exhibited weight gain during the study.

Applicant's summary and conclusion

Interpretation of results:

other: Not a skin sensitiser

Remarks:

according to EU CLP (EC 1272/2008 and its amendments)

Conclusions:

The test material was considered to be a non-sensitiser under the conditions of the test.

Executive summary:

In a local lymph node assay, performed according to OECD Guideline 429 and GLP, four groups of 5 CBA/Jcr female mice were treated on the dorsal surface of both ears once per day for 3 days with 25%, 50% or 100% (v/v) of the test substance or the vehicle alone (acetone/olive oil in a ratio of 4:1). In addition, 5 animals were treated similar with alpha-hexylcinnamaldehyde as positive control. Five days after the first topical application of the test material, the mice were injected intravenously with 3H-methyl thymidine in phosphate buffered saline. Five hours later, the mice were euthanized and the draining auricular lymph nodes were removed. The lymph node cells were precipitated with 5% trichloroacetic acid (TCA) and the pellets counted in a scintillation counter to determine incorporation of the 3H-thymidine. Exposure to the test substance at 25, 50 and 100% (v/v) resulted in stimulation indices of 2.97, 1.84, and 2.39. For the positive control, an EC3 of 13.3 was calculated, showing the validity of the test. Therefore, the test material is considered to be a non-sensitiser under the conditions of the test.