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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
04 May 2010- 14 June 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report date:
2010

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of study:
mouse local lymph node assay (LLNA)

Test material

Constituent 1
Chemical structure
Reference substance name:
magnesium dinitrate hexahydrate
Cas Number:
13446-18-9
Molecular formula:
H12MgN2O12
IUPAC Name:
magnesium dinitrate hexahydrate
Constituent 2
Chemical structure
Reference substance name:
Magnesium nitrate
EC Number:
233-826-7
EC Name:
Magnesium nitrate
Cas Number:
10377-60-3
Molecular formula:
HNO3.1/2Mg
IUPAC Name:
magnesium dinitrate
Test material form:
solid: flakes
Details on test material:
- Name of test material (as cited in study report): Magnesium nitrate hexahydrate
- Physical appearance: White solid flakes

In vivo test system

Test animals

Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS (CBA/J mice)
- Source: Charles River France, L’Arbresle Cedex, France.
- Age at study initiation: Young adult animals (approx. 11 weeks old)
- Weight at study initiation: 20-25 gram. Body weight variation was within +/- 20% of the sex mean.
- Housing: Individual housing in labeled Macrolon cages (MI type; height 12.5 cm) containing sterilized sawdust as bedding material (Litalabo, S.P.P.S., Argenteuil, France). Paper (Enviro-dri, Wm. Lillico & Son (Wonham Mill Ltd), Surrey, United Kingdom) was supplied as cage-enrichment.
The paper was removed on Day 1 prior to dosing and was supplied again after scoring of the ears on Day 3. During the acclimatization period the accommodation was as described above except that the animals were group housed in Macrolon cages (MIII type; height 18 cm).
- Diet (e.g. ad libitum): Free access to pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany).
- Water (e.g. ad libitum): Free access to tap water.
- Acclimation period: The acclimatization period was at least 5 days before the start of treatment under laboratory conditions. Accommodation was as described above except that the animals were group housed in Macrolon cages (MIII type; height 18 cm).
- Health inspection: A health inspection was performed prior to treatment, to ensure that the animals are in a good state of health. Special attention was paid to the ears, which were intact and free from any abnormality.
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.1 – 22.9ºC
- Humidity (%): 43 - 81% Deviations from the maximum level of relative humidity (70%) occurred. Laboratory historical data do not indicate an effect of the deviations
- Air changes (per hr): approximately 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours artificial fluorescent light and 12 hours darkness per day.

IN-LIFE DATES: From: 04 May 2010 To: 14 June 201

Study design: in vivo (LLNA)

Vehicle:
dimethylformamide
Remarks:
from Merck, Darmstadt, Germany
Concentration:
0-10-25-50%
No. of animals per dose:
5
Details on study design:
RANGE FINDING TESTS:
- Compound solubility:The vehicle was selected based on trial formulations performed at NOTOX and on test substance data supplied by the sponsor.
- Irritation: A preliminary irritation study was conducted in order to select the highest test substance concentration to be used in the main study. In principle, this concentration should be well tolerated systemically by the animals and may give moderate irritation (maximally grade 2; see section 6.6) at the highest concentration.
Two test substance concentrations were tested; a 25% and 50% concentration. The highest concentration was the maximum concentration as required in the test guidelines (50% for solids).
The test system, procedures and techniques were identical to those used during Days 1 to 3 of the main study unless otherwise specified. Two young adult animals were selected (Source: Janvier, Le Genest-Saint-Isle, France; Age: 8-14 weeks old). Each animal was treated with one concentration on three consecutive days. Approximately 3-4 hours after the last exposure, the irritation of the ears was assessed. Bodyweights were determined on Day 3. The animals were sacrificed after the final observation and no necropsy was performed.
- Lymph node proliferation response: Not determined in the preliminary irritation study.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Mouse LLNA (Local Lymph Node Assay).
- Criteria used to consider a positive response: DPM values are presented for each animal and for each dose group. A Stimulation Index (SI) is calculated for each group. The SI is the ratio of the DPM/group compared to DPM/vehicle control group.
If the results indicate a SI ≥ 3, the test substance may be regarded as a skin sensitizer, based on the test guideline and recommendations done by ICCVAM.
The results were evaluated according to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) of the United Nations (2007) and the Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labeling and packaging of substances and mixtures.
Consideration was given to the EC3 value (the estimated test substance concentration that will give a SI =3).


TREATMENT PREPARATION AND ADMINISTRATION:
The test substance formulations (w/w) were prepared within 4 hours prior to each treatment. No adjustment was made for specific gravity of the vehicle. Homogeneity was obtained to visually acceptable levels.
Three groups of five animals were treated with one test substance concentration per group. The highest test substance concentration was selected from the preliminary irritation study.
One group of five animals was treated with vehicle.

Induction - Days 1, 2 and 3
The dorsal surface of both ears was epidermally treated (25 μL/ear) with the test substance concentration, at approximately the same time per day. The concentrations were mixed thoroughly using a vortex mixer immediately prior to dosing.
The control animals were treated the same as the experimental animals, except that the vehicle was administered instead of the test substance.

Excision of the nodes - Day 6
All animals:
Each animal was injected via the tail vein with 0.25 mL of sterile phosphate buffered saline (PBS) (Merck, Darmstadt, Germany) containing 20 μCi of 3H-methyl thymidine (PerkinElmer Life and Analytical Sciences, Boston, MA, US).
After approximately five hours, all animals were killed by intraperitoneal injection with Euthasol® 20% (AST Farma BV, Oudewater, The Netherlands). The draining (auricular) lymph node of each ear was excised.
The relative size of the nodes (as compared to normal) was estimated by visual examination and abnormalities of the nodes and surrounding area were recorded. The nodes were pooled for each animal in approximately 3 mL PBS.

Tissue processing for radioactivity - Day 6
A single cell suspension of lymph node cells (LNC) was prepared in PBS by gentle separation through stainless steel gauze (diameter 125 μm). LNC were washed twice with an excess of PBS by centrifugation at 200g for 10 minutes at 4ºC. To precipitate the DNA, the LNC were exposed to 5% trichloroacetic acid (TCA) (Merck, Darmstadt, Germany) and stored in the refrigerator until the next day.

Radioactivity measurements - Day 7
Precipitates were recovered by centrifugation, resuspended in 1 mL TCA and transferred to 10 mL of Ultima Gold cocktail (PerkinElmer Life and Analytical Sciences, Boston, MA, US) as the scintillation fluid. Radioactive measurements were performed using a Packard scintillation counter (2800TR). Counting time was to a statistical precision of ± 0.2% or a maximum of 5 minutes whichever came first. The scintillation counter was programmed to automatically subtract background and convert Counts Per Minute (CPM) to Disintegrations Per Minute (DPM).

Observations
Mortality/Viability: Twice daily.
Toxicity: At least once daily.
Body weights: On Days 1 (pre-treatment) and 6.
Necropsy: No necropsy was performed according to protocol.
Irritation: On Day 3 (3-4 hours after treatment), the skin reactions were assessed. Skin reactions were graded according to the numerical scoring system described in "Any other information on materials and methods incl. tables.". Furthermore descriptions of all other (local) effects were recorded.
Positive control substance(s):
other: The results of a reliability test with Alpha-hexylcinnamicaldehyde, performed not more than 6 months previously, are summarized in the appendix. Similar procedures were used in the reliability test and in this study.
Statistics:
Not performed.

Results and discussion

Positive control results:
The six-month reliability check with Alpha-hexylcinnamicaldehyde indicates that the Local Lymph Node Assay as performed at NOTOX is an appropriate model for testing for contact hypersensitivity. See attached document "Reliability check".

In vivo (LLNA)

Resultsopen allclose all
Key result
Parameter:
SI
Value:
0.6
Test group / Remarks:
10%
Key result
Parameter:
SI
Value:
0.4
Test group / Remarks:
25%
Key result
Parameter:
SI
Value:
0.4
Test group / Remarks:
50%
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: see Remark
Remarks:
Mean DPM/animal values for the experimental groups treated with test substance concentrations 10, 25 and 50% were 531, 365 and 334 DPM respectively. The mean DPM/animal value for the vehicle control group was 881 DPM. See tables 3+4 of the attached document "Figures and tables".

Any other information on results incl. tables

Preliminary Irritation study (See table 1 of the attached document "table 1 and 2").

The results of the epidermal exposures for the selection of highest test substance concentration to be tested in the main study are presented in the table. Based on these results, the highest test substance concentration selected for the main study was a 50% concentration.  

Main study (See table 2 of the attached document "table 1 and 2").

The slight erythema as shown by all animals treated at 25 and 50% was considered not to have a toxicologically significant effect on the activity of the nodes. No oedema was observed in any of the animals examined.

All auricular lymph nodes of the animals of the experimental and control groups were considered normal in size. No macroscopic abnormalities of the surrounding area were noted in any of the animals.    

Body weights and body weight gain of experimental animals remained in the same range as controls over the study period. The slight body weight loss, noted in some animals, was considered not toxicologically significant.  

No mortality occurred and no symptoms of systemic toxicity were observed in the animals of the main study.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Remarks:
Not classified according to Regulation (EC) No. 1272/2008
Conclusions:
Since there was no indication that the test substance elicits an SI ≥ 3 when tested up to 50%, Magnesium nitrate hexahydrate was considered not to be a skin sensitizer. It was established that the EC3 value (the estimated test substance concentration that will give a SI =3) (if any) exceeds 50%.
Based on these results, Magnesium nitrate hexahydrate would not be regarded as a skin sensitizer according to the recommendations made in the test guidelines. It does not have to be classified and has no obligatory labeling requirement for sensitization by skin contact according to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) of the United Nations (2007) and the Regulation (EC) No 1272/2008 on classification, labeling and packaging of substances and mixtures.