Isocyanic acid, polymethylenepolyphenylene ester, 2-ethyl-1-hexanol-blocked

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

- modification: in addition, measurements of ear swelling and ear weight were done to discriminate the irritating potential from the sensitizing potential of the test substance (Integrated Model for the Differentiation of Skin reactions (IMDS))

Principles of method if other than guideline:

Modified LLNA (IMDS; Integrated Model for the Differentiation of Skin Reactions). Modifications are authorised in the OECD TG 429 and in the Note for Guidance SWP/2145/00 of the CPMP (2001). Information on validation of IMDS and scientific justification is given in: Vohr HW et al., Arch. Toxicol., 73, 501-509 (2000); Ehling G et al., Toxicology 212, 60-68 and 69-79 (2005).

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:

1-isocyanato-2-[(4-isocyanatophenyl)methyl]benzene; 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene; 2-ethylhexyl N-(4-{[4-({[(2-ethylhexyl)oxy]carbonyl}amino)phenyl]methyl}phenyl)carbamate; 2-ethylhexyl N-{4-[(4-isocyanatophenyl)methyl]phenyl}carbamate

EC Number:

700-674-2

Cas Number:

147993-65-5

Molecular formula:

Unspecified Not applicable, since UVCB

IUPAC Name:

1-isocyanato-2-[(4-isocyanatophenyl)methyl]benzene; 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene; 2-ethylhexyl N-(4-{[4-({[(2-ethylhexyl)oxy]carbonyl}amino)phenyl]methyl}phenyl)carbamate; 2-ethylhexyl N-{4-[(4-isocyanatophenyl)methyl]phenyl}carbamate

Test material form:

liquid

In vivo test system

Test animals

Species:

mouse

Strain:

NMRI

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan-Winkelmann GmbH, Borchen, Germany
- Age at study initiation: 9 weeks
- Weight at study initiation: 26-32 g
- Housing: individual
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2
- Humidity (%): 40 - 70
- Air changes (per hr): about 10
- Photoperiod (hrs dark / hrs light): 12 / 12

Study design: in vivo (LLNA)

Vehicle:

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

Concentration:

0, 1, 3, 10 %

No. of animals per dose:

6

Details on study design:

TREATMENT PREPARATION AND ADMINISTRATION:
The test item in the formulation or the vehicle were applied epicutaneously onto the dorsal part of both ears of the animals. This  treatment was repeated on three consecutive days (d1, d2 and d3). The volume administered was 25µl/ear. The used concentrations were based on the experiences with the test system and the toxic properties of the test substance.
The animals were anaesthetized by inhalation of carbon dioxide and sacrificed one day after the last application (d4). The appropriate organs were then removed. Lymphatic organs (the auricular lymph nodes) were transferred into physiological saline (PBS).
Investigations:
- weight of draining lymph nodes (given as weight index compared to vehicle controls)
- cell counts in draining lymph nodes (given as cell count index compared to vehicle controls)
Stimulation indices were calculated by dividing the absolute weight or number of cell counts of the substance treated lymph nodes by the vehicle treated ones.
- ear swelling (given in 0.01 mm and as index)
- ear weight (given in mg/8 mm diameter punch and as index)
- body weights

Positive control substance(s):

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

Statistics:

When it was statistically reasonable, the values from treated groups were compared with those from the control group by a one-way analysis of variance (ANOVA) when the variances are considered homogeneous according to a homogeneity testing like Cochran's test. Alternatively, if the variances are considered to be heterogenous (p<=0.05), a non-parametric Kruskal-Wallis test has been used (Kruskal-Wallis ANOVA) at significance levels of 5 % . Two sided multiple test procedures were done according to Dunnett or Bonferroni-Holm, respectively. Outlying values in the LN weights were eliminated at a probability level of 99% by Nalimov's method. In addition, for the LLNA/IMDS the smallest significant differentes in the means were calculated by Scheffels method, which according to Sachs can be used for both equal and unequal sample sizes.

Results and discussion

Positive control results:

Alpha hexyl cinnamic aldehyde, checked in regular intervals, showed a clear sensitizing potential in the local lymph node assay (IMDS).

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Remarks:

Stimulation index: Cell count index 10 % dose

Value:

4.58

Variability:

± 13.51 (mean ± SD in %)

Test group / Remarks:

10 % dose

Results 2

Key result

Parameter:

SI

Remarks:

Stimulation index: Cell count index 3 % dose

Value:

4.41

Variability:

± 32.30 (mean ± SD in %)

Test group / Remarks:

3 % dose

Results 3

Key result

Parameter:

SI

Remarks:

Stimulation index: Cell count index 1 % dose

Value:

2.95

Variability:

± 30.21 (mean ± SD in %)

Test group / Remarks:

1 % dose

Results 4

Key result

Parameter:

SI

Remarks:

Stimulation index: Cell count index vehicle control

Value:

1

Variability:

± 32.79 (mean ± SD in %)

Test group / Remarks:

vehicle control

Results 5

Parameter:

SI

Remarks:

Stimulation index: weight draining lymph nodes

Value:

3.59

Variability:

± 12.45 (mean ± SD in %)

Test group / Remarks:

10 % dose

Results 6

Parameter:

SI

Remarks:

Stimulation index: weight draining lymph nodes

Value:

3.03

Variability:

± 19.09 (mean ± SD in %)

Test group / Remarks:

3 % dose

Results 7

Parameter:

SI

Remarks:

Stimulation index: weight draining lyymp nodes

Value:

2.08

Variability:

± 21.73 (mean ± SD in %)

Test group / Remarks:

1 % dose

Results 8

Parameter:

SI

Remarks:

Stimulation index: weight of draining lymp nodes

Value:

1

Variability:

± 22.90 (mean ± SD in %)

Test group / Remarks:

Vehicle control

Any other information on results incl. tables

Table 1: Summary of the LLNA/IMDS results (means of 6 animals per group)

 

Parameter investigated	Vehicle control	Dose 1 %	Dose 3 %	Dose 10 %
Stimulation index: weight of draining lymph nodes	1.00	2.08 *	3.03 *	3.59 *
Stimulation index: cell count in draining lymph nodes	1.00	2.95 *	4.41 *	4.58 *
Ear swelling in 0.01 mm on day 4 (index)	17.25 (1.00)	18.75 (1.09)	20.17 * (1.17)	21.92 * (1.27)
Ear weight in mg / 8 mm diameter punch on day 4 (index)	10.79 (1.00)	11.38 (1.05)	12.36 * (1.15)	13.58 * (1.26)

 

* statistically significant increase (p ≤ 0.05)

 

All dose groups (1, 3 and 10 %) of the NMRI mice showed a clear increase in the weights of the draining lymph nodes and in the stimulation indices for cell counts compared to control animals after application of the Desmodur MT. The "positive level" which is 1.4 for cell count indices has been exceeded in all dose groups. These increases are of statistical significance.

 

The "positive level" of ear swelling which is 2 x10-2 mm increase, i.e. about 10% of the control values, has been exceeded in the mid and high dose group. A statistical significant increase of the ear weights and ear swelling compared to control animals was also detected for the mid and high dose group. An increase in this parameter would point to an acute irritating (inflammatory) response. However, such an irritating property could also be combined with a strong skin sensitizing potential of a test compound.

 

The body weights of the animals were not affected by any treatment.

 

Taken together, a specific activation of the cells of the immune system via dermal route was determined after application of 1, 3 and 10 % Desmodur MT by the method used. Thus, Desmodur MT has to be classified as a skin sensitizer.

Applicant's summary and conclusion

Interpretation of results:

Category 1 (skin sensitising) based on GHS criteria

Remarks:

The results obtained would indicate a strong sensitizing potential in the LLNA. However a significant increase compared to vehicle treated animals regarding ear swelling and ear weights was detected in the mid and high dose group which is indicative for an acute irritant (inflammatory) response. Such an irritant property can also be combined with a strong skin sensitizing potential of a test compound. There are indications that irritation can contribute to a mild unspecific stimulation of lymphocyte proliferation (McGarry 2007) which can lead to a bias in response indicating a strong sensitizing potential in the LLNA. In addition, human observation with MDI indicated a rather moderate skin sensitizing potential for MDI (Schlede et al., 2003). Assuming a bias response in the LLNA by irritation a classification with skin sensitizing category 1 (H317) with no sub-categorization is seen warranted for MDI MT.

Conclusions:

Desmodur MT was investigated in the modified local lymph node assay (LLNA-IMDS) on female mice according to OECD TG 429. Concentrations of 0 (vehicle control), 1, 3 and 10 % formulated in acetone/olive oil (4:1) were tested. The results show that Desmodur MT has a sensitizing potential in mice after dermal application. Compared to vehicle treated animals there was a significant increase regarding the weights of the draining lymph nodes and the cell counts in all dose groups. The corresponding cell count indices were 2.95, 4.41 and 4.58 exceeding the "positive level" of index 1.4. The results obtained would indicate a strong sensitizing potential in the LLNA. However a significant increase compared to vehicle treated animals regarding ear swelling and ear weights was detected in the mid and high dose group which is indicative for an acute irritant (inflammatory) response. Such an irritant property can also be combined with a strong skin sensitizing potential of a test compound. There are indications that irritation can contribute to a mild unspecific stimulation of lymphocyte proliferation (McGarry 2007*) which can lead to a bias in response indicating a strong sensitizing potential in the LLNA. In addition, human observation with MDI indicated a rather moderate skin sensitizing potential for MDI (Schlede et al., 2003). Assuming a bias response in the LLNA by irritation a classification with skin sensitizing category 1 (H317) with no sub-categorization is seen warranted for MDI MT.


*McGarry, H. F. (2007). The murine local lymph node assay: Regulatory and potency considerations under REACH. Toxicology 238:71-89.

Schlede, E., Aberer, W., Fuchs, T., Gerner, I., Lessmann, H., Maurer, T., Rossbacher, R., Stropp, G., Wagner, E., and Kayser, D. (2003). Chemical substances and contact allergy--244 substances ranked according to allergenic potency. Toxicology, 193, (3), 219-59.

Executive summary:

Desmodur MT was investigated in the modified local lymph node assay (LLNA-IMDS) on female mice according to OECD TG 429. Concentrations of 0 (vehicle control), 1, 3 and 10 % formulated in acetone/olive oil (4:1) were tested. The results show that Desmodur MT has a strong sensitizing potential in mice after dermal application. Compared to vehicle treated animals there was a significant increase regarding the weights of the draining lymph nodes and the cell counts in all dose groups. The corresponding cell count indices were 2.95, 4.41 and 4.58 exceeding the "positive level" of index 1.4. A significant increase compared to vehicle treated animals regarding ear swelling and ear weights was detected in the mid and high dose group. An increase in this parameter would point to an acute irritant (inflammatory) response. However, such an irritant property can also be combined with a strong skin sensitizing potential of a test compound. There are indications that irritation can contribute to a mild unspecific stimulation of  lymphocyte proliferation (McGarry 2007*) which can lead to a bias in response indicating a strong sensitizing potential in  the LLNA. In addition, human observation with MDI indicated a  rather moderate skin sensitizing potential for MDI (Schlede et al., 2003). Assuming a bias response in the LLNA by irritation a classification with skin sensitizing category 1 (H317) with no sub-categorization is seen warranted for MDI MT.

 

McGarry, H. F. (2007). The murine local lymph node assay: Regulatory and potency considerations under REACH. Toxicology 238:71-89.

Schlede, E., Aberer, W., Fuchs, T., Gerner, I., Lessmann, H., Maurer, T., Rossbacher, R., Stropp, G., Wagner, E., and Kayser, D. (2003). Chemical substances and contact allergy--244 substances ranked according to allergenic potency. Toxicology, 193, (3), 219-59.