L-tryptophan

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007-02-14 to 2007-02-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study according to OECD guideline 429 (adopted 2002)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

L-tryptophan

EC Number:

200-795-6

EC Name:

L-tryptophan

Cas Number:

73-22-3

Molecular formula:

C11H12N2O2

IUPAC Name:

L-tryptophan

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

Source: Harlan Italy s.r.l.
Weight: 16-20 g
Age: ca. 7-8 weeks
Acclimatisation period: 5 days
Housing: individually in polycarbonate cages with a stainless steel mesh lid
Diet: 4RF18 ad libitum
Water: ad libitum

Environmental conditions:
Temperature (°C): 22 ± 2
Relative humidity (%): 55 ± 15
Photoperiod (hrs dark / hrs light): 12 / 12 by fluorescent tubes
Air changes (per hr): 15-20

Study design: in vivo (LLNA)

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

0 (vehicle controls), 5, 10 and 25% (w/v)

No. of animals per dose:

5 females

Details on study design:

Each group of mice was treated for 3 consecutive days by topical application to the dorsal surface of each ear with 25 μl of the appropriate concentration of the test or control item. The application volume was spread over the entire dorsal surface of the ear. Animals of the negative control group received the selected vehicle only, given by the same route of administration as the test item. Five days after the first treatment, 20 μCi of [3]H-methyl thymidine diluted in sterile phosphate buffered saline were administered to each animal by intravenous injection in the tail vein. The dose volume was 250 μl. Approximately five hours later, the animals were sacrificed and the auricular lymph nodes were excised from each animal. 3H-methyl thymidine incorporation was measured by a β-scintillation counter in the prepared cell suspensions.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

The significance of the differences amongst groups was assessed by analysis of variance. Differences between the treated group and the control group were assessed by Dunnett's test using a pooled error variance. The homogeneity of the data was verified by Bartlett's test before Dunnett's test. If data were found to be inhomogeneous a Modified t test (Cochran and Cox) was applied. The mean values, standard deviations and statistical analysis were calculated from the actual values in the computer without rounding off.

Results and discussion

Positive control results:

In the group treated with the positive control item, the increase in [3]HTdR incorporation was clearly observed. The calculated SI was > 3 at the tested dose-level (SI = 20.45).

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Remarks on result:

other: 5% group: 0.77 10% group: 0.7 25% group: 1.64 positive control group: 20.45

Results 2

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: Mean dpm/animal or dpm/node: vehicle control group: 224 / 112.2 5% group: 171.4 / 86 10% group: 155.8 / 78.2 25% group: 366.6 / 192.4 positive control group: 4580.6 / 2290.6

Applicant's summary and conclusion

Interpretation of results:

not sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The potential of L-tryptophan to induce skin sensitisation was assessed by using the murine local lymph node assay in a GLP study according to OECD guideline 429. Five groups, each of 5 female mice, were treated with the test item at concentrations of 5, 10 and 25%, with the reference item alpha-Hexylcinnamaldehyde at the concentration of 25%, and with the vehicle alone (Acetone/olive oil 4:1). No statistically significant increase in [3]HTdR incorporation was observed in animals treated with the test item when compared to the negative control group. The calculated SI was lower than 3 at all dose-levels tested. Reliability check was positive as expected. No reaction, indicating a potential systemic effect, was observed after treatment at any of the dose-levels investigated. No signs of local irritation were observed at application sites.
Therefore, it can be concluded that L-tryptophan did not elicit any sensitisation response.