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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:
From 24 August, 2001 to 01 September, 2001
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study was conducted according to acceptable scientific principles; in compliance with GLP. However, because the test substance is a surfactant, a second step (dye binding) should have been performed.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: Rat Skin Transcutaneous Electrical Resistance (TER) Test INVITTOX no. 115
Principles of method if other than guideline:
The skin corrosivity potential of the test substance was assessed using the Transcutaneous Electrical Resistance Assay (TER). This method is based on the fact that corrosive substances produce an irreversible loss of normal stratum comeum integrity and function, which can be measured as a reduction in the inherent transcutaneous electrical resistance (TER) below a corrosive threshold level (i.e., 5kΩ).
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Physical state: Pale yellow liquid
- Batch No.: 0730004891941
- Storage condition of test material: Room temperature in the dark

Test animals

Species:
rat
Strain:
Wistar
Details on test animals and environmental conditions:
Male Wistar rats (Crl: (WI) BR), obtained from Charles River (UK) Limited, Margate, Kent, were used for the in vitro TER assay.

Test system

Type of coverage:
open
Preparation of test site:
other: Skin discs, obtained from the pelts of humanely killed young Crl (WI) BR Wistar strain rats
Vehicle:
unchanged (no vehicle)
Controls:
yes
Amount / concentration applied:
A volume of 150 µL of the test substance was applied to the inner epidermal surface using an automatic pipettor
Duration of treatment / exposure:
1, 4 and 24 h
Observation period:
1, 4 and 24 h
Details on study design:
SKIN DISC PREPARATION:
The animals were humanely killed by inhalation of a rising concentration of CO2 followed by cervical dislocation. The animals were in the telogen phase of hair growth and little or no hair growth was visible. The quality of the stratum corneum was critical to the success of the assay and so the stage of hair growth was controlled by using animals of exactly the correct age. When the animals had been humanely killed the dorsal skin was removed from each 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 (1 54 mM MgSO4).
Each disc had to give a resistance value of between 10 kΩ and 25 kΩ in order for the remainder of the pelt to be used in the assay.


TEST SUBSTANCE APPLICATION:
The test substance was applied to the epidermal surface of three skin discs per time point. The test substance was applied for contact periods of 1 h, 4 h and 24 h. The test substane was used as supplied. A volume of 150 µL was applied to the inner epidermal surface using an automatic pipettor.
At the end of the exposure period, the test substance was removed by washing the skin disc with a jet of warm tap water for approximately 10 seconds until no further test substance could be removed.


CONTROLS:
As part of a quality control procedure, a positive and negative control disc 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 h.


DETERMINATION OF TRANSCUTANEOUS ELECTRICAL RESISTANCE (TER):
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 secs. 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 for each time point.

Results and discussion

In vitro

Resultsopen allclose all
Irritation / corrosion parameter:
other:
Value:
7
Remarks on result:
other:
Remarks:
Basis: mean. Time point: 1 h. Remarks: standard deviation = 3.8. (migrated information)
Irritation / corrosion parameter:
other:
Value:
2.6
Remarks on result:
other:
Remarks:
Basis: mean. Time point: 4 h. Remarks: standard deviation = 2.2. (migrated information)
Irritation / corrosion parameter:
other:
Value:
2.2
Remarks on result:
other:
Remarks:
Basis: mean. Time point: 24 h. Remarks: standard deviation = 3.8. (migrated information)

In vivo

Irritant / corrosive response data:
The mean TER recorded for the 1 h test substance contact periods was greater than 5 kΩ.
The mean TER recorded for the 4 h and 24 h test substance contact periods was less than 5 kΩ.
The TER recorded for the positive and negative control discs were as follows:
- Hydrochloric acid (approximately 36%), Positive control disc: 683 Ω (0.683 kΩ)
- Sterile distilled water, negative control disc: 21.7 kΩ

Any other information on results incl. tables

According to the guideline INVITTOX no. 115, in case TER values below 5 kilo-Ohm are found, and in case the test substance is a surfactant, then a dye binding study (Sulforrhodamine B) should have been performed to determine whether this would be a false positive result. This has not been done.

Applicant's summary and conclusion

Interpretation of results:
other: has a potential to be corrosive to the skin in vivo.
Remarks:
Criteria used for interpretation of results: expert judgment
Conclusions:
Based on an in vitro transcutaneous electrical resistance (TER) assay, the test substance was considered to have the potential to be corrosive to the skin in vivo.
Executive summary:

An in vitro transcutaneous electrical resistance (TER) assay was conducted to assess the skin corrosivity potential of the test substance (50% active ingredient) using skin discs obtained from the pelts of humanely killed young Crl (WI) BR Wistar rats. The test substance was applied to the epidermal surface of three skin discs per contact period, 1, 4, and 24 hours. At the end of the contact period the test substance was removed using a jet of warm tap water. Corrosive substances are found to produce an irreversible loss of normal stratum corneum integrity and function which can be measured as a reduction in the inherent TER. A threshold value of 5kΩ has been established below which substances are considered likely to be corrosive in vivo. The mean electrical resistance measured using low voltage alternating current electronic databridge after 1, 4 and 24 hours was 7, 2.6 and 2.2 kΩ. Under the conditions of the test, the test substance was considered to have the potential to be a skin corrosive (Sanders A, 2002).