Fatty acids, C8-12, isopentyl esters

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Study period:

21 Apr - 10 May 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP guideline study with acceptable restrictions.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

Isopropyl laurate

EC Number:

233-560-1

EC Name:

Isopropyl laurate

Cas Number:

10233-13-3

Molecular formula:

C15H30O2

IUPAC Name:

isopropyl laurate

Details on test material:

- Name of test material (as cited in study report): Isopropyl laurate
- Physical state: clear colourless liquid
- Analytical purity: 99.4 ± 0.2%
- Lot/batch No.: 7000876+7000948 combined
- Expiration date of the lot/batch: 04 February 2012
- Storage condition of test material: at room temperature in the dark

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Janvier, Le Genest-Saint-Isle, France
- Age at study initiation: young adult animals (approx. 9 weeks old)
- Weight at study initiation: weight variation was within +/- 20% of the sex mean
- Housing: Individual housing in labelled Makrolon cages (MI type; height 12.5 cm) containing sterilized sawdust as bedding material (Litalabo, S.P.P.S., Argenteuil, France). Paper (Enviro-dri, Wm. Lillico & Son (Wonham Mill Ltd), Surrey, United Kingdom) was supplied as cage-enrichment. The paper was removed on Day 1 prior to dosing and was supplied again after scoring of the ears on Day 3.
- Diet: Pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany), ad libitum.
- Water: Tap water, ad libitum.
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.0 ± 3.0 (actual range: 18.9 – 22.6)
- Humidity (%): 40 - 70 (actual range: 37 - 84)
- Air changes (per hr): 15
- 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:

RANGE FINDING TESTS:
- Irritation: A preliminary irritation study was conducted in order to select the highest test substance concentration to be used in the main study. In principle, this concentration should be well tolerated systemically by the animals and may give moderate irritation. Two test substance concentrations were tested; a 50% and 100% concentration. The highest concentration was the maximum concentration as required in the test guidelines (undiluted for liquids).

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Local Lymph Node Assay (LLNA)
- Criteria used to consider a positive response: If the results indicate a SI ≥ 3, the test substance may be regarded as a skin sensitizer, based on the test guideline and recommendations done by ICCVAM.The results were evaluated according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (2007) and the Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures. The EC3 value (the estimated test substance concentration that will give a SI =3) was determined, using linear interpolation.

TREATMENT PREPARATION AND ADMINISTRATION:
The dorsal surface of both ears was epidermally treated (25 μL/ear) with the test substance, at approximately the same time per day. The concentrations were mixed thoroughly using a vortex mixer immediately prior to dosing. The control animals were treated the same as the experimental animals, except that the vehicle was administered instead of the test substance. Radioactive measurements were performed using a Packard scintillation counter (2800TR). Counting time was to a statistical precision of ± 0.2% or a maximum of 5 minutes whichever came first. The scintillation counter was programmed to automatically subtract background and convert Counts Per Minute (CPM) to Disintegrations Per Minute (DPM).

Positive control substance(s):

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

Results and discussion

Positive control results:

The six-month reliability check with Alpha-hexylcinnamicaldehyde indicates that the Local Lymph Node Assay as performed at NOTOX is an appropriate model for testing for contact hypersensitivity.

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Remarks on result:

other: The SI values calculated for the substance concentrations 25, 50 and 100% were 1.7, 3.5 and 5.1 respectively.

Results 2

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: Mean DPM/animal values for the experimental groups treated with test substance concentrations 25, 50 and 100% were 620, 1324 and 1929 DPM respectively. The mean DPM/animal value for the vehicle control group was 375.

Any other information on results incl. tables

Table 1: Skin reactions, body weights and relative size auricular lymph nodes

group	test substance^1 (% w/w)	an^2	Day 1	Day 3				Day 6
			bw (g)^3	skin reactions dorsal surface ear				bw (g)^3	size nodes^4
				left		right			left	right
				erythema	oedema	erythema	oedema
1	0%	1	22	0	0	0	0	23	n	n
	(vehicle)	2	21	0	0	0	0	22	n	n
		3	22	0	0	0	0	22	n	n
		4	22	0	0	0	0	22	n	n
		5	23	0	0	0	0	24	n	n
2	25%	6	22	0	0	0	0	22	n	n
		7	22	0	0	0	0	22	n	n
		8	23	0	0	0	0	23	n	n
		9	23	0	0	0	0	23	n	n
		10	23	0	0	0	0	22	n	n
3	50%	11	23	1	0	1	0	25	+	+
		12	21	1	0	1	0	21	+	+
		13	24	1	0	1	0	24	+	+
		14	23	1	0	1	0	24	+	+
		15	23	1	0	1	0	23	+	+
4	100%	16	23	1	0	1	0	22	+	+
		17	21	1	0	1	0	20	+	+
		18	24	1	0	1	0	24	+	+
		19	22	1	0	1	0	23	+	+
		20	23	1	0	1	0	22	+	+

¹Vehicle: Acetone/Olive oil (4:1 v/v).

²Animal number.

³Body weight (grams).

⁴Relative size auricular lymph nodes (-, -- or ---: degree of reduction, +,++ or +++: degree of enlargement, n: considered to be normal).

 

Table 2: Radioactivity measurements (individual animals)

group	test substance^1(% w/w)		animal	DPM / animal
1	0%	1		375
	(Vehicle)	2		340
		3		328
		4		551
		5		281
2	25%	6		718
		7		423
		8		427
		9		401
		10		1130
3	50%	11		1364
		12		1806
		13		1224
		14		1093
		15		1135
4	100%	16		2283
		17		1429
		18		2219
		19		1878
		20		1835

¹Vehicle: Acetone/Olive oil (4:1 v/v).

Applicant's summary and conclusion

Interpretation of results:

ambiguous

Remarks:

Migrated information as the observed effects could be due to skin irritation.

Conclusions:

At test substance concentrations of 50 and 100% erythema and increased size of auricular lymph nodes occurred. The ear thickness was not measured, therefore an ear swelling was not reported. Thus, it cannot be excluded, that the observed effects were caused by local skin irritation, rather than by skin sensitisation. A clear interpretation of the results was therefore not possible.