Hexan-6-olide

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 November to 9 December 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

Hexan-6-olide

EC Number:

207-938-1

EC Name:

Hexan-6-olide

Cas Number:

502-44-3

Molecular formula:

C6H10O2

IUPAC Name:

oxepan-2-one

Constituent 2

Reference substance name:

e-caprolactone

IUPAC Name:

e-caprolactone

Details on test material:

The test material was Capa Monomer (CAS 502-44-3), batch no. WNI 5874. One container, holding approximately 1000 mL of test item, was received under ambient
conditions at Charles River, Edinburgh on 17 September 2009. Upon arrival, the test item, a liquid, was stored at ambient temperature, protected from light and under nitrogen. A purity value of 99.93% and an expiry date of 16 March 2010 were supplied by the Sponsor.

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

The animals were female (nulliparous and non-pregnant) mice of the CBA/Ca strain. All animals were supplied by Charles River UK Ltd. They were 7 to 8 weeks old and weighed 16.4 to 20.0 g on despatch. The mice were acclimatised for at least 8 days. On arrival, the animals were removed from
their transport box in random order and were allocated to dose group by placing them in cages labelled with at least study number, animal number and group. Each animal received a subcutaneous implant which identified it individually within the study and which corresponded to that animal's number.
The animals were housed in groups of 2 or 3 in polycarbonate cages (dimensions 36.5 x 20.7 x 14 cm) with stainless steel grid tops and integrated food hoppers. Wood shavings were used as bedding and nesting material (‘Nestlets’) was provided. A wooden chewstick, supplied by Tapvei Oy, Finland, was placed in each cage as environmental enrichment. Analysis did not provide evidence of contamination that might have prejudiced the outcome of the study. Each cage was supplied with a water bottle.
Average daily environmental temperatures were approximately 21°C on each day of the observation period and the range for average daily relative humidity was approximately 43 to 62 %. A 12 h light/dark cycle was in operation (light hours normally 0700 to 1900 h) with a minimum of 15 air changes per hour.
Rat and Mouse No. 1 Maintenance Diet (Special Diets Services, UK) and water taken from the public supply (Scottish Water, UK) were available ad libitum throughout the study. The results of diet and water analyses did not provide evidence of contamination and so the outcome of the study was not prejudiced.

Study design: in vivo (LLNA)

Vehicle:

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

Concentration:

Preliminary study: 100%
Main study: 0%, 25%, 50% and 100%

No. of animals per dose:

5 female mice/dose

Details on study design:

A preliminary study was conducted with two females and a formulation concentration of 100%. There were no signs of systemic toxicity or local irritation and no effect on body weight was noted. Therefore, dose concentrations of 25%, 50% and 100% were selected as suitable non-toxic doses for
administration in the main study.

Preliminary study: For 3 consecutive days (Days 1 to 3) animals received an open application of 25 μL of undiluted test item onto the dorsum of each ear. There was no further treatment. All animals were examined for reaction to treatment. Observations were conducted frequently on each day of dosing (predose, immediately post dose and approximately 1 and 2 h after dosing) and once daily thereafter until sacrifice on Day 8. The animals were then discarded.

Main study: For 3 consecutive days (Days 1 to 3) animals received an open application of 25 μL of the appropriate formulation onto the dorsum of each ear. There was no treatment on Days 4 and 5. All animals were examined for reaction to treatment. On each day of dosing the observations were conducted predose, immediately post dose and approximately 1 and 2 h post dose. Thereafter animals were observed once daily until the kill on Day 6 (the day of the thymidine injection). On Day 6 each animal received an intravenous injection (250 μL) of phosphate buffered saline (PBS) containing approximately 20 μCi of [methyl-³H] thymidine into the lateral tail vein.
Approximately 5 h after intravenous administration all animals were killed by exposure to a rising concentration of carbon dioxide and the major blood vessels were severed to exsanguinate. Each pair of draining auricular lymph nodes was collected from each animal and the animal was then discarded. A single cell suspension of lymph node cells from each paired sample was prepared by gentle disaggregation through a 200 μm mesh stainless steel gauze. The lymph nodes cells were washed in excess of PBS (approximately 1 mL) and then centrifuged at approximately 1300 g for 10 min at 4°C. The supernatant was drawn off and the mesh discarded and the pellet was washed a second time with approximately 1 mL PBS and then centrifuged (also at approximately 1300 g for 10 min at 4°C). Following centrifugation, the supernatant was discarded and the pellet was precipitated with approximately 1 mL 5% trichloroacetic acid at 2 to 8oC for approximately 18½ h. The pellet was again centrifuged at approximately 1300 g for 10 min at 4°C and the supernatant discarded. The pellet was then re-suspended in 200 μL ‘Solvable’ and the suspension transferred to a vial containing 10 mL scintillation fluid. Incorporation of tritiated thymidine was measured by β-scintillation counting and was expressed as disintegrations per minute (DPM).

All animals were checked for viability early in the morning and again as late as possible on each day. The body weight of each individual animal was recorded on Day 1 (before the first dose) and on Day 6.

Positive control substance(s):

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

Statistics:

No formal statistical analysis was carried out.

Results and discussion

Positive control results:

The stimulation indices in a recent positive control study were 1.2, 1.5 and 5.0 for 5%, 10% and 25% hexylcinnamicaldehyde, respectively.

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Value:

0.9

Test group / Remarks:

100% test group

Results 2

Parameter:

SI

Value:

1.2

Test group / Remarks:

50% test group

Results 3

Parameter:

SI

Value:

1.1

Test group / Remarks:

25% test group

Results 4

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: The group mean DPM for mice treated with the test item at concentrations of 0%, 25%, 50% or 100% were 1702, 1912, 2017 and 1461 respectively.

Any other information on results incl. tables

No systemic signs and no signs of local irritation were noted in any animal during the observation period. Body weight gains were considered to be acceptable for mice of this age and strain.

Individual and group mean scintillation counts (DPM)

Treatment	Animal	DPM	Group Mean DPM	Stimulation Index
0% (vehicle only)	1	906	1702	1
	2	1731
	3	1345
	4	2544
	5	1986
25% Capa Monomer	6	1165	1912	1.1
	7	1389
	8	2820
	9	2999
	10	1185
50% Capa Monomer	11	2886	2017	1.2
	12	2478
	13	2629
	14	700
	15	1393
100% Capa Monomer	16	1869	1461	0.9
	17	1732
	18	1790
	19	717
	20	1195

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of the study, since treatment with Capa Monomer at concentrations of up to 100% (ie undiluted Capa Monomer) did not achieve a stimulation index of ≥3, it was considered that the test item does not have the potential to cause sensitisation.

Executive summary:

This study investigated the delayed contact hypersensitivity potential of the test item, Capa Monomer, in a LLNA using CBA/Ca mice. A preliminary test was conducted using 2 females. Each mouse received an open application of 25 μL of undiluted Capa Monomer onto the dorsum of each ear on 3 consecutive days. There was no evidence of systemic toxicity or local irritation and, as a result of these findings, formulation concentrations were selected for the main study. Three groups, each consisting of 5 females, were treated in the same manner as the preliminary test mice with concentrations prepared at 25%, 50% or 100% (ie undiluted Capa Monomer), respectively, also for 3 consecutive days. The vehicle was acetone:olive oil (4:1 v/v) and one group of 5 females received only this and acted as controls. Three days after the final application each animal received an intravenous injection of [methyl-³H] thymidine into the lateral tail vein and 5 h later the draining lymph nodes were collected in order that incorporation of tritiated thymidine could be assessed by scintillation counting. There were no systemic signs noted in any animal during the observation period and body weight changes were considered to be acceptable for mice of this age and strain. The stimulation index (SI) values for the mice treated with Capa Monomer at concentrations of 25%, 50% or 100%, when compared with the control group, were 1.1, 1.2 and 0.9, respectively.

Under the conditions of the study, since treatment with Capa Monomer at concentrations of up to 100% (ie undiluted Capa Monomer) did not achieve a stimulation index of ≥3, it was considered that the test item does not have the potential to cause sensitisation. Capa Monomer does not meet the criteria for classification as a sensitiser according to EU labelling regulations.