Butyl 3-mercaptopropionate

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10 Dec 2008 - 15 Jan 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayerisches Landesamt für Arbeitsschutz, Arbeitsmedizin und Sicherheitstechnik

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

Isooctyl 3-mercaptopropionate

EC Number:

250-157-6

EC Name:

Isooctyl 3-mercaptopropionate

Cas Number:

30374-01-7

Molecular formula:

C11H22O2S

IUPAC Name:

isooctyl 3-mercaptopropionate

Details on test material:

- Name of test material (as cited in study report): Isooctyl mercaptopropionate
- Analytical purity: 99.88 GC
- Purity test date: 2008-10-08
- Lot/batch No.: 25051
- Expiration date of the lot/batch: 2009-10-07
- Physical state: colourless liquid
- Storage: at room temperature

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Janvier, F - 53940 Le Genest-Saint-Isle (SPF)
- Age at study initiation: 8 -12 weeks
- Weight at study initiation: 180 - 240 mg
- Housing: The animals were barrier maintained (semi-barrier) in an air conditioned room. Animals were kept in IVC cages, type II L, Polysulphone c ages on Altromin saw fiber bedding.
- Diet (ad libitum): Altromin 1324 maintenance diet for rats and mice - maintenance
- Water (ad libitum): free access to tap water, sulphur acidified to a pH value of approx. 2.8 (drinking water, municipal residue control, microbiologi cally controlled at regular intervals)
- Acclimation period: at least 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): rel. humidity: 55 ± 10
- Air changes (per hr): at least 10 times per hour
- Photoperiod (hrs dark / hrs light): artificial light, sequence being 12 hours light, 12 hours dark

Study design: in vivo (LLNA)

Vehicle:

other: acetone/olive oil (3:1 v/v)

Concentration:

12.5, 25.0 and 50.0 % (diluted with AOO)

No. of animals per dose:

5

Details on study design:

Preliminary test: (Detection of the maximum limit application solution)
One animal was treated by topical application to the entire dorsal surface of each ear with the test item at a concentration of 100 % an d two animals were treated with 50 %. One animal was treated in the same way with 100 % of the negative control. Cageside observatio ns included spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoe, asphyxia, vocalization, diarrhoea, chan ges in the skin and fur, eyes and mucuous membranes (salivation, discharge).The animal treated with 100 % was found dead by day 2 . Neither signs of systemic toxicity nor signs of irritation at the application site could be detected in the animals treated with a conce ntration of 50 %.


MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 3
- Exposure period: 3 days
- Test groups: 3
- Control group: 1 negative control group
- Site: entire dorsal surface of each ear
- Frequency of applications: daily
- Duration: 6 days
- Concentrations: 12.5, 25 and 50 % (diluted with AOO)



TREATMENT PREPARATION AND ADMINISTRATION: Test item preparations were made immediately prior to each dosing. The vehicle served as negative control. Each mouse was treated by topical application of 25 μl of the selected solution to the entire dorsal surface of each ear. The topical applications were performed once daily over three consecutive days.
Five days after the first topical application all mice were dosed with 20 μCi 3H-methyl thymidine, diluted to a working concentration of 80 μCi/ml.
Approximately 5 hours after the 3H-methyl thymidine-injection all mice were sacrificed. The draining "auricular lymph nodes" were excised and individually pooled for each animal (2 lymph nodes per animal) and collected in phosphate buffered saline (PBS). A single cell suspension of pooled lymph node cells was prepared by gentle mechanical disaggregation through polyamide gauze (200 mesh size). After washing the gauze with PBS the cell suspension was pelleted in a centrifuge. The supernatant was discarded and the pellets were resuspended with PBS. This washing procedure was repeated.
After the final wash each pellet was resuspended in approximately 1 ml 5 % trichloro acetic acid (TCA) and 5 ml scintillation fluid was added. Then this solution was transferred into scintillation vials and stored at room temperature overnight.

The 3H-methyl thymidine - incorporation was measured in a ß-counter and expressed as the number of disintegrations per minute (DPM). Similarly, background 3H-methyl thymidine levels were also measured (5 % TCA). The determination of radioactivity was performed individually for each animal.

Positive control substance(s):

other: historical: P-Phenylenediamine (CAS 106-50-3, Sigma, purity > 98 %; Lot 057K0052), 1 % on 3 consecutive days

Results and discussion

Positive control results:

Positive controls are performed periodically (last test was October 2008) and displayed expected values.

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Value:

5.1

Variability:

±1.6

Test group / Remarks:

12.5%

Results 2

Parameter:

SI

Value:

5.6

Variability:

±2.9

Test group / Remarks:

25%

Results 3

Parameter:

SI

Value:

9.5

Variability:

±2.7

Test group / Remarks:

50%

Results 4

Parameter:

EC3

Value:

8.2

Remarks on result:

other: linear extrapolation

Any other information on results incl. tables

At the daily clinical observation the animals did not show any visible clinical symptoms.

The EC3 value (derived by linear interpolation) could not be stated, as all measure points were above the stimulation index of three.

If the EC3 is estimated by linear extrapolation, an EC3 of 8.2% is estimated.

Applicant's summary and conclusion

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Conclusions:

Considering the reported data of this sensitization test, it can be stated that the test article Isooctyl mercaptopropionate causes reactions identified as sensitization, as the stimulation index was above 3.0 for each concentration tested.

Executive summary:

The sensitising properties of iOMP were evaluated in a Local lymph node assay according to OECD tG 429.

Based on the results of the preliminary test the test item Isooctyl mercaptopropionate was assayed for sensitising properties at concentrations
of 12.5%, 25% and 50% (v/v). The vehicle used was Acetone/Olive Oil (AQO).

All of the three tested concentrations of the test item reached the stimulation index of 3.
The stimulation index at a concentration of 12.5% was 5.1
The stimulation index at a concentration of 25% was 45.6
The stimulation index at a concentration of 50% was 9.5
At the daily clinical observation the animals did not show any visible clinical symptoms.