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EC number: 606-330-7 | CAS number: 195008-76-5
Index LN weights LN Cell Count Index
0.5% 1.1 1.1
0.6% 1.1 1.0
2.5% 1.5 1.63
Ear weight Index compared to control
0.5% 26.4 1.0
1.0% 27.2 1.1
2.5% 30.7* 1.2
EC3 = (a-c) [(3-d)/(b-d)] + c = 1.7 % (w/w)
a,b,c,d = Co-ordinates of the two pairs of data lying immediately above and below the S.I. value of 3 on the LLNA dose response plot.
In this study the test item was assessed for its skin sensitising potential using the Local Lymph Node Assay (LLNA) in mice. Test item solution at different concentrations was prepared in the vehicle acetone:olive oil (4+1 v/v). For this purpose a local lymph node assay was performed using test item concentrations of 0.5, 0.6% and 2.5% (w/w). The highest concentration tested was the highest concentration that could be technically used and applied whilst avoiding systemic toxicity and excessive local skin irritation (as determined by three pre-experiments).
The animals did not show any signs of systemic toxicity or local skin irritation during the course of the study and no cases of mortality were observed. However, a statistically significant increase in ear weight was observed in the high dose group in comparison to the vehicle control group (p<0.05). Furthermore, the cutoff-value for a positive response regarding the ear weight index of 1.1 reported for BALB/c mice (see Ref. 9) was exceeded in this group (index of 1.2).
A test item is regarded as a sensitiser in the LLNA if exposure to one or more test item concentration results in a 3-fold or greater increase in incorporation of 3HTdR compared with concurrent controls, as indicated by the Stimulation Index (S.I.). The estimated test item concentration required to produce a S.I. of 3 is referred to as the EC3 value. In this study Stimulation Indices (S.I.) of 1.44, 1.87, and 4.27 were determined with the test item at concentrations of 0.5%, 0.6% and 2.5% (w/w) in acetone:olive oil (4+1 v/v), respectively. A dose response was observed. The EC3 value calculated was 1.5 % (w/w).
A statistically significant increase in DPM value was observed in all test item treated groups in comparison to the vehicle control group (p<0.05), in the mid and high dose group, this increase was also considered as biologically relevant. Furthermore, a statistically significant and biologically relevant increase in lymph node weight and cell count was determined in the highest dose group and the cutoff-value for a positive response regarding the lymph node cell count index of 1.55 reported for BALB/c mice was exceeded in this group (index of 1.63). Based on the above mentioned findings regarding ear skin irritation, an influence of irritation on lymphocyte proliferation cannot be excluded. Nevertheless, on the basis of the present data, the test item has to be classified as a sensitiser.
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