Naphthenic acids, cobalt salts

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

no data available

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Reasonably well conducted study. Positive controls are not given. Test procedure with modification of the standard LLNA, but according to the author, the used method have comparable sensitivity to the radioactive original method.

Data source

Reference

Reference Type:

publication

Title:

Allerginicity and cross-reactivity of naphthenic acid and ist metallic salts in experimental animals.

Author:

Yamano, T.; et al.

Year:

2006

Bibliographic source:

Contact Derm. 54, 25-28

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The method to test the reactivity of CoCl2 was performed by the modified method of the standard LLNA with some modification.

GLP compliance:

no

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

Naphthenic acids, cobalt salts

EC Number:

263-064-0

EC Name:

Naphthenic acids, cobalt salts

Cas Number:

61789-51-3

IUPAC Name:

λ²-cobalt(2+) bis(3-(3-ethylcyclopentyl)propanoate)

Details on test material:

- Name of test material (as cited in study report): cobalt naphthenate
- Molecular weight (if other than submission substance): 397.42 g/mol
- Physical state: solid
No further details are given.

In vivo test system

Test animals

Species:

mouse

Strain:

Balb/c

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: CLEA Japan (Tokyo, Japan)
No details are given.

Study design: in vivo (LLNA)

Vehicle:

other: petrolatum

Concentration:

25 µL of 0.3%, 1%, 3% or 10%

No. of animals per dose:

4 mice

Details on study design:

RANGE FINDING TESTS:
No data available, if a range finding test was performed.

MAIN STUDY
TREATMENT PREPARATION AND ADMINISTRATION: Mice were exposed to 25 µL of various concentrations through application to the dorsum of both ears for 3 consecutive days (days 0-2). On day 4, 5-bromo-2'-deoxyuridine (BrdU) was administered i.p. to each mouse. The next day, a pair of auricular lymph nodes from each mouse was excised. After counting the total cell numbers from each mouse, BrdU concentrations were measured by enzyme-linked immunosorbent assay.

EVALUATION
Total lymph node cell count in a dosed animal divided by mean lymph node cell count in a control group was designated as a cellularity index, whereas BrdU incorporation per unit number of cells from a dosed animal divided by mean BrdU incorporation from a control group was used as a BrdU.incorporation index. A LLNA-stimulation index was calculated by multiplying the cellularity indey by the BrdU-incorporation index. At the time of lymph node excision, the thickness of the ears was measured with a digital micrometer. Ear thickness of a dosed animal divided by mean ear thickness of a control group was designated as ear-thickness index.

Positive control substance(s):

not specified

Statistics:

Index values for each dosed group and vehicle-control group were compared via Dunnett's or Steel's multiple comparison method using a Statlight software package.

Results and discussion

Positive control results:

no data

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Value:

ca. 1.75

Test group / Remarks:

1 % concentration

Remarks on result:

other: Test substance exhibited significant increase in the LLNA-stimulation index values at the respective highest doses tested. Minimum induction dose for Cobalt naphthenate was 1% (see attached figure).

Results 2

Key result

Parameter:

SI

Value:

ca. 12

Test group / Remarks:

3 % concentration

Results 3

Key result

Parameter:

SI

Value:

ca. 12.5

Test group / Remarks:

10 % concentration

Applicant's summary and conclusion

Interpretation of results:

other: potential skin sensitiser

Conclusions:

Cobalt naphthenate applied in concentration >1% can be evaluated as a potential skin sensitiser.

Executive summary:

Female BALB/c mice (4 per group) were treated with 25 µl of various concentrations (0.3, 1, 3 and 10 %) of Cobalt naphthenate in pet. or with petrolatum alone (vehicle control). The test substance was applied to the dorsum of both ears for 3 days. On day 4, 5-bromo-2'-deoxyuridine (BrdU) was administered i.p. The next day, a pair of auricular lymph nodes were excised. Total cell numer was counted and total BrdU concentrations were measured by enzyme-linked immunosorbent assay.A stimulation index was determined: BrdU incorporation per unit number of cells from treated animals compared to controls.