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Toxicological information

Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
The study was performed between 23 February 2010 and 01 March 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:
other: EU Guideline Testing of Chemicals B46
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Version / remarks:
draft version
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Test material form:
solid: particulate/powder

In vitro test system

Test system:
human skin model
Source species:
human
Cell type:
non-transformed keratinocytes
Vehicle:
unchanged (no vehicle)
Details on test system:
RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN Model kit
- Tissue batch number(s): not specified
- Production date: not specified
- Shipping date: not specified
- Delivery date: 23 February 2010
- Date of initiation of testing:

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: room temperature
- Temperature of post-treatment incubation: 37°C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: For rinsing a wash bottle containing PBS with Ca++ and Mg++ was used. Rinsing was achieved by filling and emptying each tissue insert for approximately 40 seconds using a constant soft stream of PBS to gently remove any residual test material.
- Observable damage in the tissue due to washing: not reported
- Modifications to validated SOP: none reported

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/mL
- Incubation time: 3 hours
- Spectrophotometer: Anthos 2001 microplate reader
- Wavelength: 540 nm
- Filter: no reference filter
- Linear OD range of spectrophotometer: not specified

NUMBER OF REPLICATE TISSUES: 3

NUMBER OF INDEPENDENT TEST SEQUENCES / EXPERIMENTS TO DERIVE FINAL PREDICTION: 1

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- The test substance is considered to be irritant to skin if the viability after 15 minutes exposure and 42 hours post-exposure is less than or equal to 50%
- The test substance is considered to be irritant to skin if the viability after 15 minutes exposure and 42 hours post-exposure is greater than 50%
- Justification for the selection of the cut-off point(s) if different than recommended in TG 431 and 439:
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
TEST MATERIAL
- Amount(s) applied: 10 mg

VEHICLE
none, the epidermis has previously moistened with 5µL sterile distilled water

NEGATIVE CONTROL
- Amount(s) applied: 10 µL PBS

POSITIVE CONTROL
- Amount(s) applied: 10 µL SDS
- Concentration: 5% w/v
Duration of treatment / exposure:
15 minutes
Duration of post-treatment incubation (if applicable):
42 hours
Number of replicates:
3

Results and discussion

In vitro

Results
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
15 min
Value:
90.6
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Remarks:
6.4%
Remarks on result:
no indication of irritation
Other effects / acceptance of results:
- OTHER EFFECTS:
- Visible damage on test system: not reported
- Direct-MTT reduction: no
- Colour interference with MTT: no

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: The mean OD540 for the negative control treated tissues was ≥0.6 and the SD value of the percentage viability was ≤20%. The negative control acceptance criterion was therefore satisfied.
- Acceptance criteria met for positive control: The relative mean tissue viability for the positive control treated tissues was ≤40% relative to the negative control treated tissues and the standard deviation value of the percentage viability was ≤20%.  The positive control acceptance criterion was therefore satisfied.

Any other information on results incl. tables

Table1 : Mean OD540 Values and Percentage Viabilities for the Negative Control Material, Positive Control Material and Test Material

Material

OD540of tissues

Mean OD540of triplicate tissues

±SDof OD540

Relative individual tissue viability (%)

Relative mean viability (%)

± SD of Relative mean viability (%)

Negative Control Material

0.647

0.664

0.017

97.4

100*

2.5

0.664

100.0

0.680

102.4

Positive Control Material

0.060

0.043

0.015

9.0

6.4

2.2

0.035

5.3

0.033

5.0

Test Material

0.599

0.602

0.024

90.2

90.6

3.6

0.580

87.3

0.627

94.4

SD=    Standard deviation

*=     The mean viability of the negative control tissues is set at 100%


Table2 : Qualitative Evaluation of Tissue Viability (MTT uptake visual evaluation)

Material

Tissue 1

Tissue 2

Tissue 3

Negative Control Material

-

-

-

Positive Control Material

++

++

++

Test Material

-

-

-

MTT visual scoring scheme
-          =         blue tissue (viable)
+         =         blue/white tissue (semi-viable)
++       =         tissue is completely white (dead

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The test material was considered to be Non-Irritant (NI). This study is conducted according to an appropriate validated in vitro guideline and under the conditions of GLP and therefore the study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement as a key study for this endpoint. In addition, the data is considered to be adequate and reliable for classification and labelling in accordance with Regulation (EC) No. 1272/2008 (EU CLP). Magnesium hydrogenorthophosphate is not considered to be classified in accordance with Regulation (EC) No. 1272/2008 (EU CLP).
Executive summary:

Introduction: The purpose of this test was to evaluate the skin irritation potential of the test material using the EPISKINTMreconstituted human epidermis model after a treatment period of 15 minutes followed by a post-exposure incubation period of 42 hours. The principle of the assay was based on the measurement of cytotoxicity in reconstituted human epidermal cultures following topical exposure to the test material by means of the colourimetric MTT reduction assay. Cell viability is measured by enzymatic reduction of the yellow MTT tetrazolium salt (3 -[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) to a blue formazan salt (within the mitochondria of viable cells) in the test material treated tissues relative to the negative controls. The concentration of the inflammatory mediator IL-1α in the culture medium retained following the 42 hour post-exposure incubation period is also determined for test materials which are found to be borderline non-irritant based upon the MTT reduction endpoint. This complimentary end-point will be used to either confirm a non-irritant result or will be used to override the non-irritant result.

Methods:

Triplicate tissues were treated with the test material for an exposure period of 15 minutes. At the end of the exposure period each tissue was rinsed before incubating for approximately 42 hours. At the end of the post-exposure incubation period each tissue was taken for MTT-loading. The maintenance medium from beneath each tissue was transferred to pre-labelled micro tubes and stored in a freezer for possible inflammatory mediator determination. After MTT loading a total biopsy of each epidermis was made and placed into micro tubes containing acidified isopropanol for extraction of formazan crystals out of the MTT-loaded tissues. 

At the end of the formazan extraction period each tube was mixed thoroughly and duplicate 200 µl samples were transferred to the appropriate wells of a pre-labelled 96-well plate. The optical density was measured at 540 nm.

Data are presented in the form of percentage viability (MTT reduction in the test material treated tissues relative to negative control tissues).

Results: 

The relative mean viability of the test material treated tissues was 90.6% after a 15-minute exposure.

Quality criteria: 

The quality criteria required for acceptance of results in the test were satisfied.

Conclusion:  The test material was considered to be Non-Irritant (NI).