2-mercaptopropionic acid

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From April 26, 2002 to August 30, 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2002

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2-mercaptopropionic acid

EC Number:

201-206-5

EC Name:

2-mercaptopropionic acid

Cas Number:

79-42-5

Molecular formula:

C3H6O2S

IUPAC Name:

2-sulfanylpropanoic acid

Test material form:

liquid

In vitro test system

Test system:

human skin model

Remarks:

EpiDerm Skin Model (MatTek, Ashland, MA, USA).

Source species:

other:

Cell type:

other:

Cell source:

other:

Source strain:

other:

Details on test system:

EpiDerm™ Skin Model Kit
Supplier: MatTek Corporation, Ashland, MA, USA

24 x EpiDerm Tissues
Lot number: 4006, Kit F
Storage conditions: approximately 4 °C in the dark

Assay Medium
Lot numbers: 4006 and 3064100
Storage conditions: approximately 4 °C in the dark

Ca++Mg++ free Dulbecco’s phosphate buffered saline (DPBS)
Lot numbers: 4N071102PAA and 3060726
Storage conditions: room temperature

MTT Assay Kit:
Supplier: MatTek Corporation, Ashland, MA, USA

MTT Diluent:
Lot number: 1135871
Storage conditions: approximately 4 °C in the dark

MTT Concentrate (5 mg/ml):
Lot number: 07112002ACA
Storage conditions: deep frozen at approximately –18 °C in the dark

MTT Extractant
Lot number: X10B07
Storage conditions: room temperature in the dark

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

50 μL of test substance

Duration of treatment / exposure:

3 minutes and 60 minutes

Number of replicates:

duplicates

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 minutes exposure

Value:

9.36

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Results 2

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 minutes exposure.

Value:

6.6

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Other effects / acceptance of results:

Corrective Procedure:

The mean OD540 of the untreated killed control was subtracted from the mean OD540 of the treated killed control for the triplicate aliquots.
The mean OD540 of the test substance treated killed control less the mean OD540 of the untreated killed control was 0.05. This figure is not significant to suggest there has been interference by direct reduction of MTT by the test substance. Therefore the MTT reduction in the test substance treated viable tissues is ascribed to the viable cells only.

Quality Criteria:

The mean OD540 of the two negative control tissues were 1.977 for the 3 min exposure and 1.986 for the 60 min exposure. These both met test acceptance criteria (i.e. mean OD540 ≥ 0.8).
Potassium Hydroxide as a 8.0 n solution was used as a positive reference. A 3 min application of 8.0 n Potassium Hydroxide revealed a mean relative tissue viability of 5.51 %. The assay met the acceptance criteria (i.e. mean relative tissue viability of the 3 min positive control was ≤ 30 %).
In addition to the positive and negative control quality criteria, a difference of >30 % between two tissues treated identically is regarded as a rejection criterion and re-testing of the chemical is recommended if the resulting viability is near to a classification cut-off. For all duplicate tissues in this study, the difference in viabilities between tissues was ≤30 % in all cases.

Applicant's summary and conclusion

Interpretation of results:

Category 1 (corrosive) based on GHS criteria

Conclusions:

Under the study conditions, the relative mean viability was 9.36% after 3 min exposure, and 6.60% after 60 min exposure. The relative mean viability of the test substance-treated tissues was <10% after 3 min exposure. In conclusion, the test substance is considered to be corrosive to skin.

Executive summary:

A study was conducted to determine the corrosivity potential of the test substance using the EpiDerm Skin Model according to OECD Guideline 439, in compliance with GLP. The experimental design of the study consists of a test for Direct Reduction of MTT by the test substance, followed by the main study. For the main study, duplicate EpiDerm tissues were treated with 50 μL of the test substance and exposed for 3 min and 60 min. The tissues were incubated at 37°C in a humidified atmosphere of 5% CO2 in air for the appropriate exposure times. Negative control-treated tissues (50 μL sterile, distilled water), and positive control-treated tissues (8.0 n Potassium Hydroxide), were treated concurrently. At the end of the exposure period each EpiDerm tissue was rinsed using Dulbecco’s phosphate buffered saline according to the modified rinsing procedure and placed into a ‘holding plate’, until all of the tissues had been treated and rinsed. They were then transferred to an MTT ‘loading plate’, and incubated at 37°C for 3 h in a humidified atmosphere of 5% CO2 in air. At the end of this time, each EpiDerm tissue was blotted dry and placed into an MTT ‘extraction plate’ in order to extract all of the reduced MTT from the tissues. At the end of the extraction period, the extracted MTT solution was mixed for each EpiDerm tissue and 3 x 200 μL samples for each tissue were transferred to the appropriate wells of a 96 well plate. The absorbency at 540 nm (OD540) of each well was measured with the Anthos 2001 microplate reader. Data are presented in the form of % viability (MTT conversion relative to negative controls) for each of the two exposure times. The ability of the test substance to directly reduce MTT in the direct MTT reduction test proved inconclusive. There was a possibility that if the test substance could not be totally rinsed off the EpiDerm tissues, that any residual test substance present on the tissue may directly reduce MTT and could have given rise to a false negative result. Therefore a corrective procedure using a “freeze killed” control EpiDerm tissue, also treated with the test substance, was necessary to quantify this possibility. The quality criteria required for acceptance of results in the test were satisfied. Under the study conditions, the relative mean viability was 9.36% after 3 min exposure, and 6.60% after 60 min exposure. The relative mean viability of the test substance-treated tissues was <10% after 3 min exposure. In conclusion, the test substance is considered to be corrosive to skin (Warren, 2002).