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Skin irritation / corrosion

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Administrative data

Endpoint:
skin corrosion: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
The study was performed between 18 July 2012 and 19 July 2012.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted to GLP and in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not effect the quality of the relevant results.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 430 (In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test Method (TER))
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Test material form:
other: solid

Test animals

Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
One female Wistar (RccHan™:WIST) strain rat was supplied by Harlan Laboratories U.K. Ltd. At the start of pelt preparation the rat was twenty one to twenty three days old.

Test system

Controls:
other: not applicable.
Amount / concentration applied:
The test item was used as supplied. Sufficient test item was applied to cover the epidermal surface.
Duration of treatment / exposure:
24 hours.
Details on study design:
PRE-TEST PROCEDURES:
SKIN DISC PREPARATION:
Following an acclimatisation period of two days the animal was shaved to remove hair from the dorsal surface. The shaved area was washed using an antibiotic wash. After three days a second antibiotic wash was performed. Two days later the animal was killed using ascending concentrations of carbon dioxide followed by cervical dislocation. The animal was in the telogen phase of hair growth and little or no hair growth was visible.

When the animal had been humanely killed the dorsal skin was removed from the rat as a single pelt. Care was taken during the procedure to avoid unnecessary damage to the pelt. Excess fat was removed and the pelt mounted, epidermal side uppermost, onto a polytetrafluoroethylene (PTFE) tube. The tissue was secured in place using a rubber “O” ring. Excess tissue was trimmed away and the “O” ring/PTFE interface sealed with soft paraffin wax. The tube was supported by a clamp inside a labelled 30 ml glass receptacle containing 10 ml electrolyte solution (154 mM MgSO4).

SKIN DISC QUALITY CONTROL
Two skin discs of approximately 0.79 cm2 were taken from the pelt and the TER measured as a quality control procedure. Each disc had to give a resistance value of greater than 10 kΩ in order for the remainder of the pelt to be used in the assay (Appendix 1 - see any other information on materials and methods incl. tables section). If either disc fell below the 10 kΩ threshold, the pelt was discarded. The quality control discs were then discarded and new discs from the acceptable pelt were mounted on the PTFE tubes.

PROCEDURE:
TEST ITEM ADMINISTRATION:
The test item was applied to the epidermal surface of three skin discs for a contact period of 24 hours.

Sufficient test item was applied to cover the epidermal surface. At the end of the exposure period, the test item was removed by washing the skin disc with a jet of warm tap water until no further test item could be removed.

As part of a Quality Control procedure, three positive and negative control discs were assayed. The positive control was hydrochloric acid (approximately 36%) and the negative control was sterile distilled water. The contact period for the positive and negative controls was 24 hours.

DETERMINATION OF TRANSCUTANEOUS ELECTRICAL RESISTANCE:
The TER was measured using a Wheatstone Bridge with a low voltage alternating current. Prior to measurement of the resistance, the surface tension of the skin disc was reduced by adding a sufficient volume of 70% ethanol to cover the epidermis. The ethanol was removed by inverting the tube after approximately 3 seconds. The PTFE tube was then placed in the labelled receptor chamber and the tissue was hydrated by the addition of 3 ml MgSO4 solution (154 mM) to the inside of the PTFE tube. Any air bubbles present were dislodged by tapping the tube.

The stainless steel electrodes of the databridge were placed on either side of the skin disc. The measurement was taken and a value in Ω/kΩ per skin disc was displayed on the databridge display. The mean TER for the skin discs was calculated.

INTERPRETATION OF RESULTS:
Results are accepted on the condition of adherence to the ranges given. If the mean positive and negative control results for the assay do not fall within the accepted ranges, the data on the test substance cannot be interpreted as being reliable, and the experiment must be repeated.

Hydrochloric acid (approximately 36%), Positive control range: 0.5 to 1.0 kΩ
Sterile distilled water, Negative control range: 10 to 25 kΩ

The test substance will be classified as ‘Non-Corrosive’ if the mean TER value recorded for the 24 hour contact period is greater than 5 kΩ.

The test substance will be classified as ‘Corrosive’ if the mean TER value recorded for the 24 hour contact period is 5 kΩ or lower.






Results and discussion

In vitro

Results
Irritation / corrosion parameter:
other: other: Mean TER
Value:
4.4
Remarks on result:
other:
Remarks:
Basis: mean. Time point: 24 hour. Remarks: the test item was considered to have the potential to cause corrosion in vivo.. (migrated information)

Any other information on results incl. tables

Results

Individual and mean TER measurements for the test item and the positive and negative control items are given in Table 1.

The mean TER recorded for the test item was less than 5 kΩ.

On visual inspection the skin discs appeared pale and slightly thin.

The mean TER recorded for the positive and negative control discs were as follows:

Positive control disc, Hydrochloric acid (approximately 36%):  686 Ω
Negative control disc, Sterile distilled water:                             18.5 kΩ

Table 1              Individual and Mean TER Measurements

Treatment

Tissue Number

TER

Mean TER

Standard Deviation

Test Item

1         

4.4 kΩ

4.4 kΩ

±0.2

2         

4.6 kΩ

3         

4.3 kΩ

Positive Control

4         

810 Ω

686 Ω

±117.6

5         

672 Ω

6         

576 Ω

Negative Control

7         

16.5 kΩ

18.5 kΩ

±4.4

8         

15.5 kΩ

9         

23.6 kΩ

Applicant's summary and conclusion

Interpretation of results:
corrosive
Remarks:
Migrated information
Conclusions:
Following assessment of the data the test item was considered to have the potential to cause corrosion in vivo.
Executive summary:

Introduction. 

The skin corrosivity potential of the test item was assessed using the Transcutaneous Electrical Resistance (TER) Assay. The method was designed to be compatible with the following:

- OECD Guidelines for the Testing of Chemicals No. 430 “In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test (TER)” (adopted)

Methods. 

The integrity of the pelt was confirmed using a Quality Control test. The test item was applied to the epidermal surface of three skin discs for a contact period of 24 hours. At the end of the contact period the test item was removed using a jet of warm tap water. Corrosive substances produce an irreversible loss of normal stratum corneum integrity and function, this is measured as a reduction in the inherent TER. Test items that give a mean electrical resistance of 5 kΩ or less are considered likely to be corrosive in vivo. The TER was measured using a low voltage alternating current electronic databridge.

Results.

The results are summarised as follows:

Test Item Contact Period

Mean Electrical Resistance
(standard deviation)

24 Hours

4.4 kΩ

(±0.2)

Conclusion. 

Following assessment of the data the test item was considered to have the potential to cause corrosion in vivo.