Trichloro(N,N-dimethyloctylamine)boron

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Testing was conducted between the 21st May 2014 and 17th June 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The in vitro skin sensitisation study was initiated before the entry into force of the amendments to Annex VII.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2014

Report date:

2014

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:

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

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:

Trichloro(N,N-dimethyloctylamine)boron

EC Number:

252-200-4

EC Name:

Trichloro(N,N-dimethyloctylamine)boron

Cas Number:

34762-90-8

Molecular formula:

C10H23BCl3N

IUPAC Name:

dimethyl(octyl)(trichloro-λ⁵-boranylidene)amine

Test material form:

liquid: viscous

Details on test material:

Identification: trichloro(N,N-dimethyloctylamine)boron (TK 12146)
Batch: AEC0123100
Purity: 100%
Harlan description:
Huntsman description: brown solid block
solid, yellow to brown
Expiry date: 15 March 2017
Storage Conditions: room temperature in the dark

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

Female CBA/Ca (CBA/CaOlaHsd) strain mice were supplied by Harlan Laboratories UK Ltd., Oxon, UK. On receipt the animals were randomly allocated to cages. The animals were nulliparous and non pregnant. After an acclimatization period of at least five days the animals were selected at random and given a number unique within the study by indelible ink marking on the tail and a number written on a cage card. At the start of the study the animals were in the weight range of 15 to 23 g, and were eight to twelve weeks old.

The animals were group housed in suspended solid floor polypropylene cages furnished with softwood woodflakes. Free access to mains tap water and food (2014C Teklad Global Rodent diet supplied by Harlan Laboratories UK Ltd., Oxon, UK) was allowed throughout the study.

The temperature and relative humidity were set to achieve limits of 19 to 25 °C and 30 to 70%, respectively. The rate of air exchange was approximately fifteen changes per hour and the lighting was controlled by a time switch to give twelve hours continuous light (06.00 to 18.00) and twelve hours darkness.

The animals were provided with environmental enrichment items which were considered not to contain any contaminant of a level that might have affected the purpose or integrity of the study.

Justification:
Mice are the preferred species of choice since quantitative methods have been developed for the measurement of skin sensitization responses in the mouse and are specified in the appropriate test guidelines.

Study design: in vivo (LLNA)

Vehicle:

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

Concentration:

Groups of four mice were treated with the test item at concentrations of 25%, 10% or 5% w/w in acetone/olive oil 4:1.

No. of animals per dose:

Groups of four mice were treated with the test item at concentrations of 25%, 10% or 5% w/w in acetone/olive oil 4:1.

Details on study design:

RANGE FINDING TESTS:
Preliminary Screening Test:
Using available information regarding the systemic toxicity/irritancy potential of the test item, a preliminary screening test was performed using two mice, one mouse per test item concentration. The mice were treated by daily application of 25 µL of the test item at concentrations of 50% and 25% w/w in acetone/olive oil 4:1, to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The mice were observed twice daily on Days 1, 2 and 3 and once daily on Days 4, 5 and 6. Local skin irritation was scored daily according to the scale for Erythema. Any clinical signs of toxicity, if present, were also recorded. The body weight of each mouse was recorded on Day 1 (prior to dosing) and on Day 6.

The thickness of each ear was measured using a Mitutoyo 547 300S gauge (Mitutoyo Corporation), pre dose on Day 1, post dose on Day 3 and on Day 6. Any changes in the ear thickness were noted. Mean ear thickness changes were calculated between time periods Days 1 and 3 and Days 1 and 6. A mean ear thickness increase of equal to or greater than 25% was considered to indicate excessive irritation and limited biological relevance to the endpoint of sensitization.

MAIN STUDY:
TREATMENT PREPARATION AND ADMINISTRATION:
Groups of four mice were treated with the test item at concentrations of 25%, 10% or 5% w/w in acetone/olive oil 4:1. The preliminary screening test suggested that the test item would not produce systemic toxicity or excessive local skin irritation at the highest suitable concentration. 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 four mice received the vehicle alone in the same manner.

3H-Methyl Thymidine Administration:
Five days following the first topical application of the test item or vehicle (Day 6) all mice were injected via the tail vein with 250 µL of phosphate buffered saline (PBS) containing 3H methyl thymidine (3HTdR: 80 µCi/mL, specific activity 2.0 Ci/mmoL, ARC UK Ltd) giving a total of 20 µCi to each mouse.

OBSERVATIONS:
Observations:
Clinical Observations: All animals were observed twice daily on Days 1, 2 and 3 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.

Body Weights: The body weight of each mouse was recorded on Day 1 (prior to dosing) and Day 6 (prior to termination).

TERMINATION:
Five hours following the administration of 3HTdR all mice were killed by carbon dioxide asphyxiation. The draining auricular lymph nodes from the four mice were excised and pooled for each experimental group. For each group 1 mL of PBS was added to the pooled lymph nodes.

Preparation of Single Cell Suspension: A single cell suspension of pooled lymph node cells was prepared by gentle mechanical disaggregation through a 200 mesh stainless steel gauze. The lymph node cells were rinsed through the gauze with 4 mL of PBS into a petri dish labeled with the study number and dose concentration. The lymph node cell suspension was transferred to a centrifuge tube. The petri dish was washed with an additional 5 mL of PBS to remove all remaining lymph node cells and these were added to the centrifuge tube. The pooled lymph node cells were pelleted at 1400 rpm (approximately 190 g) for ten minutes. The pellet was resuspended in 10 mL of PBS and re pelleted. To precipitate out the radioactive material, the pellet was re suspended in 3 mL of 5% Trichloroacetic acid (TCA).

Determination of 3HTdR Incorporation: After approximately eighteen hours incubation at approximately 4 °C, the precipitates were recovered by centrifugation at 2100 rpm (approximately 450 g) for ten minutes, re suspended in 1 mL of TCA and transferred to 10 mL of scintillation fluid (Optiphase 'Trisafe'). 3HTdR incorporation was measured by ß scintillation counting. The "Poly Q™" vials containing the samples and scintillation fluid were placed in the sample changer of the scintillator and left for approximately twenty minutes. The purpose of this period of time in darkness was to reduce the risk of luminescence, which has been shown to affect the reliability of the results. After approximately twenty minutes, the vials were shaken vigorously. The number of radioactive disintegrations per minute was then measured using the Beckman LS6500 scintillation system (Beckman Instruments Inc, Fullerton, CA, USA).

Positive control substance(s):

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

Statistics:

Calculation of EC3 Value:
EC3 = c + [[(3-d)/(b-d)] x (a-c)]

a = 25
b = 3.42
c = 10
d = 2.04

EC3 value = 10 + [[(3-2.04)/(3.42-2.04)] x (25-10)] = 20.43

The concentration of test item expected to cause a 3 fold increase in 3HTdR incorporation (EC3 value) was calculated to be 20.43%.

Results and discussion

Positive control results:

Results:
The Stimulation Index expressed as the mean radioactive incorporation for the treatment group divided by the mean radioactive incorporation of the vehicle control group is as follows.

Concentration (% v/v) in
acetone/olive oil 4:1 Stimulation Index Result
25 12.76 Positive

Conclusion:
α Hexylcinnamaldehyde, tech., 85% was considered to be a sensitizer under the conditions of the test.

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Value:

1.52

Test group / Remarks:

5%

Results 2

Parameter:

SI

Value:

2.04

Test group / Remarks:

10%

Results 3

Parameter:

SI

Value:

3.42

Test group / Remarks:

25%

Any other information on results incl. tables

 Preliminary Screening Test:

Clinical observations, body weight and mortality data are given in Table 1* and local skin irritation is given in Table 2*. The ear thickness measurements and mean ear thickness changes are given in Table 3*.

* For tables 1 - 4 please see below.

 

No signs of systemic toxicity, visual local skin irritation or irritation indicated by an equal to or greater than 25% increase in mean ear thickness were noted with the mouse treated at a concentration of 25% w/w in acetone/olive oil 4:1. Very slight erythema on Days 2 to 4 and a greater than 25% increase in mean ear thickness were noted with the mouse treated at a concentration of 50% w/w in acetone/olive oil 4:1.

 

Based on this information the dose levels selected for the main test were 25%, 10% and 5% w/w in acetone/olive oil 4:1.

Main Test:

Estimation of the Proliferative Response of Lymph Node Cells:

The radioactive disintegrations per minute per lymph node and the stimulation index are given in Table 4*.

 

Applicant's summary and conclusion

Interpretation of results:

sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Under the study conditions, the test substance was sensitizer to skin.

Executive summary:

A study was conducted to determine the skin sensitisation potential of the test substance, trichloro(N,N-dimethyloctylamine)boron according to OECD Guideline 429 and EU Method B.42 (Local Lymph Node Assay), in compliance with GLP. Three groups, each of four CBA mice, were treated with 50 µL (25 µL per ear) of the test item as a solution in acetone/olive oil 4:1 at concentrations of 25%, 10% or 5% w/w. A further group off our animals was treated with acetone/olive oil 4:1 alone. Three days after the last exposure, all animals were injected with 3H-methyl thymidine and, after 5 h, the draining (auricular) lymph nodes were excised and pooled for each animal. After precipitation of the DNA of the lymph node cells, radioactivity measurements were performed. The activity was expressed as Disintegrations Per Minute (DPM) and a Stimulation Index (SI) was subsequently calculated for each group. The highest concentration tested was the highest concentration that could be achieved whilst avoiding systemic toxicity and excessive local skin irritation as confirmed by three pre-experiments. The Stimulation Indices (S.I.) determined with the test substance were of 1.52, 2.04, 3.42 at concentrations of 5, 10 and 25 % in acetone/olive oil (4:1, v/v), respectively. Under the study conditions, the test substance was sensitizer to skin (Harlan, 2014).