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EC number: 689-267-8 | CAS number: 501925-98-0
Main study results: stimulation indices (SI):
Group 1, negative control
Group 3, 50%
Group 4, 100%
Lymph node cell count
Lymph node weight
____ significantly different from control at p ≤ 0.01
The purpose of this study was to determine the sensitising potential of the test substance in the modified local lymph node assay in mice.
The study was performed according to OECD 429, however not employing the use of radioactive labelling to measure cell proliferation, as the radioactive method proposed by the OECD guideline led to problems in various EU laboratories: such as (i) practical difficulties/complexity of the test, in particular the radiochemical steps, which sometimes resulted in loss of specimen/activity; this in turn led to variability in the results and to a poor reproducibility and (ii) radiation protection issues. However, the OECD guideline allows other endpoints for assessment of proliferation in form oflymph node cell counts and lymph node weightsif justification and appropriate scientific support exist showing the validity of this method.
The alternative method used for the study employing thelymph node weightandlymph nodecell count to assessproliferationhas been established by an European interlaboratory validation exercise, as described in the two publications by Ehling et al. 2005a and 2005b.This method has the advantage of (i) more simplistic experimental work, (ii) less variability, (iii) better reproducibility, (iv) faster results, (v) reduced costs.
In addition, the acute inflammatory skin reaction is measured by ear weight determination of circular biopsies of the ears and ear thickness measurements on test day 1 and test day 4 to identify skin irritation properties of the test item. It is important to determine if a positive test result is due to the skin irritation potential of the test item or due to its sensitising properties.
Stimulation indices were calculated for the lymph node cell count, lymph node weight, ear weight and ear thickness by dividing the average values per group of the test item treated animals by the vehicle treated ones.
Values above 1.4 (lymph nodecell count to identify sensitisation) or 1.1 (ear weight to identify irritation) are considered positive (these values were fixed empirically during the interlaboratory validation of this method (Ehling et al. 2005a and 2005b)).
Three concentrations of1,6-Di(trimethoxysilylpropylcarbamoyloxy)hexane(25% and 50%, suspended in acetone/olive oil (3+1, v/v))(w/w) or the undiluted test item (100%) were tested in six female NMRI mice per group and compared to a vehicle control group.
In addition, a positive control group(25% solution v/v ofa-hexyl cinnamic aldehyde inacetone/olive oil (3+1, v/v)) was employed.
Stimulation indices (SI):
Treatment with the test substance at concentrations of 25%, 50% or 100% did not reveal statistical significantly increased values forlymph nodecell count. The stimulation indices of the lymph node cell count did not exceed the threshold level of 1.4. Hence, the test item is classified as not sensitising.
The threshold level for the ear weight of 1.1 was not exceeded and no increase of ear thickness was observed, i.e. no irritating properties were noted.
The positive control group caused the expected increases in lymph node cell countand lymph node weight(statistically significant at p ≤ 0.01).Therefore, the study can be regarded as valid.
No signs of local or systemic intolerance were recorded. The animal body weight was not affected by the treatment.
In conclusion, under the present test conditions, the test substance at concentrations of 25% or 50% (w/w) in acetone/olive oil (3+1, v/v) or the undiluted test item did not reveal any sensitising properties in the local lymph node assay.
Based on the results of the modified LLNA and according to the criteria of EC Directive 67/548/EEC and EC Regulation 1272/2008 the test item is not classified as sensitizing to skin.
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