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EC number: 258-904-8
CAS number: 53988-10-6
Based on results obtained in validation studies and general experiences
with this test system groups of mice were treated with vehicle, 2 %, 10
% or 50 % 1 ,3-Dihydro-4( or 5)-methyl-2H-benzimidazole-2-thione in DMF.
The NMRI mice did not show an increase in the stimulation indices for
cell counts or for weights of the draining lymph nodes after application
of the test item 1 ,3-Dihydro-4( or 5)-methyl-2H-benzimidazole-2-thione.
The "positive level", which is 1.4 for the cell count index, was never
reached or exceeded in any dose group.
The "positive level" of ear swelling, which is 2x 10E-2 mm increase,
i.e. about 10 % of the control values, has not been reached or exceeded
in any dose group.
In the high dose group deposits of the test item were standing at the
ears of one animal (no. 24), in places.
After treatment with Alpha Hexyl Cinnamic Aldehyde (group 5) the NMRI
mice showed clear increases in the weights of the draining lymph nodes
and in the stimulation indices for cell counts compared to control
animals, which are of statistical significance. The "positive level",
which is 1.4 for cell count indices, has clearly been exceeded.
The "positive level" of ear swelling, which is 2x10E-2 mm increase, i.e.
about 10 % of the control values, has been exceeded in the positive
control group. This increase was of statistical significance. A
significant increase compared to vehicle treated animals regarding ear
weights was detected, too.
It has to be clarified that the "positive levels" mentioned above are
exclusively defined for the NMRI outbreed mice used for this study Such
positive limits have to be calculated for each strain of mice
The modified Local Lymph Node Assay (IMDS) was performed on 24 female
NMRI mice of the strain HsdWin:NMRI (6 animals/ test item group and 6
control animals) to determine if there is any specific (sensitizing) or
non-specific (irritant) stimulating potential of
the test item 1 ,3-Dihydro-4( or 5)-methyl-2H-benzimidazole-2-thione.
A concurrent control of 6 animals treated with Alpha Hexyl Cinnamic
Aldehyde was included.
The study was conducted with the following test item concentrations:
Test item: 0 % (vehicle control), 2 %, 10 % and 50 %. Positive control:
30 % Alpha Hexyl Cinnamic Aldehyde
The test item was formulated in dimethylformamide (DMF) to yield a
solution in the low and mid dose and a suspension in the high dose. The
positive control was formulated in DMF to yield a solution.
Compared to vehicle-treated animals, none of the parameters measured in
the substancetreated groups, i.e. cell counts and weights of the
draining lymph nodes, ear weights and ear swelling, reached or exceeded
the "positive levels" defined for this assay [6, 8, 9]. These results
show that there is no indication for a skin sensitizing effect after
administration of a concentration up to and including 50 %
1,3-Dihydro-4(or 5)-methyl-2H-benzimidazole-2- thione in this test
In conclusion, these results show that the test item 1,3-Dihydro-4(or
5)-methyl-2Hbenzimidazole- 2-thione was not sensitising in mice after
dermal application of up to and including a 50 % concentration. No
indication for a non-specific (irritant) activation was
detected, too. Therefore, the concentration of 50 % turned out to be the
NOEL for the parameters investigated in this study with respect to skin
These results are verified by the comparison with the results of the
positive control group (Alpha Hexyl Cinnamic Aldehyde).
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