2-(2-ethoxyethoxy)-2-methylpropane

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-07-2013 to 2013-10-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP and guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2010

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

2-(2-ethoxyethoxy)-2-methylpropane

EC Number:

257-196-8

EC Name:

2-(2-ethoxyethoxy)-2-methylpropane

Cas Number:

51422-54-9

Molecular formula:

C8H18O2

IUPAC Name:

2-(2-ethoxyethoxy)-2-methylpropane

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories B.V. Postbus 6174 5960 AD Horst / The Netherlands
- Age at study initiation: Pre-test: 9 - 10 weeks (beginning of treatment), Main study: 10 - 11 weeks (beginning of treatment)
- Weight at study initiation: 20.8 +/- 1.2
- Housing: group
- Diet: 2018C Teklad Global 18% protein rodent diet (certified), ad libitum
- Water: tap water, ad libitum
- Acclimation period: 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.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2 °C
- Humidity (%): 50-94 %
- Photoperiod (hrs dark / hrs light): 6.00 a.m. - 6 p.m.

Study design: in vivo (LLNA)

Vehicle:

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

Concentration:

25, 50 % in acetone/olive oil and 100 % (undiluted test item)

No. of animals per dose:

5 (20 animals for the whole test)

Details on study design:

RANGE FINDING TESTS:
- Compound solubility: A solubility experiment was performed according to the recommendations given by OECD 429
- Irritation: To determine the highest non-irritant test concentration that at the same time did not induce signs of systemic toxicity, a pre-test was performed in two animals.
- Lymph node proliferation response: At the tested concentrations the animals did not show any signs of local skin irritation or systemic toxicity. Thus, the test item in the main study was assayed at 25%, 50% (w/w), and 100%.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Local Lymph Node assay
- Criteria used to consider a positive response: The sensitivity and reliability of the experimental technique employed was assessed by use of α-hexyl cinnamaldehyde dissolved in acetone/olive oil (4+1, v/v) (compound listed in OECD 429 Guideline) which is known to have skin sensitisation properties in mice. The periodic positive control experiment was performed using CBA/CaOlaHsd mice.


TREATMENT PREPARATION AND ADMINISTRATION:
Each test group of mice was treated by (epidermal) topical application to the dorsal surface of each ear with test item concentrations of 25% and 50% in acetone:olive oil (4+1, v/v), and 100% (undiluted test item). The application volume, 25 μL/ear/day, was spread over the entire dorsal surface (∅ ∼ 8 mm) of each ear once daily for three consecutive days. A further group of mice (control animals) was treated with an equivalent volume of the relevant vehicle alone. Five days after the first topical application (day 6) 250 μL of phosphate-buffered saline containing 19.8 μCi of 3H-methyl thymidine (equivalent to 79.0 μCi/mL 3HTdR) were injected into each test and control mouse via the tail vein.

Positive control substance(s):

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

Statistics:

The mean values and standard deviations were calculated in the body weight tables, for the ear weights, the lymph node weights and lymph node cell count, and for the DPM values (group mean DPM ± standard deviation).
A statistical analysis was conducted on the DPM values, the ear weights, the lymph node weights and the lymph node cell count to assess whether the difference was statistically significant between the test item groups and negative control group. For all statistical calculations SigmaStat for Windows (Version 2.0) was used. A One-Way-Analysis-of-Variance was used as a statistical method. In case of significant results of the One-Way-ANOVA, multiple comparisons were performed with the Dunnett test. Statistical significance was set at the five per cent level (p < 0.05).
The Dean-Dixon-Test was used for detection of possible outliers (performed with Microsoft Excel 2007). However, both biological and statistical significance were considered together.

Results and discussion

Positive control results:

0 % (Test item concentration) : DPM = 2201, SI = 1.0
5 % ((Test item concentration): DPM = 3518, SI = 1.6
10 % (Test item concentration) : DPM = 5251, SI = 2.4
25 % (Test item concentration) : DPM = 12915, SI = 5.9

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Remarks on result:

other: Control group: SI = 1.00 25 %: SI = 1.11 50 %: SI = 1.04 100 %: SI = 1.38

Results 2

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: Control group: Mean DPM = 241.5 25 %: Mean DPM = 268.9 50 %: Mean DPM = 251.5 100 %: Mean DPM = 333.3