Registration Dossier

Administrative data

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

L-phenylalanine

Link to relevant study records
Reference
Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
not specified
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 479 (Genetic Toxicology: In Vitro Sister Chromatid Exchange Assay in Mammalian Cells)
Deviations:
not specified
GLP compliance:
not specified
Type of assay:
bacterial reverse mutation assay
Target gene:
no data
Species / strain / cell type:
S. typhimurium TA 98
Additional strain / cell type characteristics:
not specified
Species / strain / cell type:
S. typhimurium TA 100
Additional strain / cell type characteristics:
not specified
Species / strain / cell type:
Chinese hamster lung fibroblasts (V79)
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Test concentrations with justification for top dose:
2.00 mg/ml
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: purified water (testing with UV-radiation), DMSO (test assays without UV-radiation)
Positive controls:
yes
Positive control substance:
sodium azide
benzo(a)pyrene
other: 2-nitrofluorene, 2-aminoanthracene, epichlorhydrine
Details on test system and experimental conditions:
The test procedure of Maron and Ames was used and the mutagenicity factor for each sample was calculated by number of revertants of test substance/plate and number of spontaneous revertants/plate (rev./pl.).
For SCE-assay V79 Chinese hamster cells were grown in minimal essential medium (MEM) with Earle’s salts supplemented with 10% fetal calf serum and antibiotics. Cells were treated with the test substance for 2.5 h. Chromosome preparation and staining were performed according to standard protocols. Epichlorhydrine (1.0; 0.5; 0.25 mM) and benzo(a)pyrene (0.08; 0.04; 0.02 mM) were used as positive controls with and without metabolic activation. For each experimental data point 25 second division metaphases were scored and the mean values of SCEs per 22 chromosomes were evaluated.
In the case of testing with UV-irradiation the compounds were dissolved in 1000 ml purified water. The samples were irradiated either by low- or high-pressure vapor UV lamps with a fluence of 2500 J/m2. UV-irradiation doses up to 10 times the doses for physical disinfection were used. Dimethylsulfoxide (DMSO) was added as organic solvent to the irradiated samples. The water phase was extracted using evaporation equipment and the remaining DMSO-phase contained the organic components. Recovery rates above 90% for each compound were determined by HPLC. In parallel experiments the organic compounds were directly dissolved in DMSO for test assays without UV-irradiation. All samples were tested for mutagenicity both with Ames- and SCE-tests.
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Positive controls validity:
valid
Species / strain:
Chinese hamster lung fibroblasts (V79)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Positive controls validity:
valid
Conclusions:
Interpretation of results (migrated information):
negative

L-phenylalanine was examined in Ames-test (bacterial strains TA 98 and TA 100) and sister chromatid exchange (SCE)-test (V79 cells) before and after UV-irradiation. Based on results in Ames- and SCE-test a mutagenic activity was not obtained for all L-phenylalanine samples, neither before nor after UV-irradiation.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

In the key study L-phenylalanine was examined in the Ames-test (bacterial strains TA 98 and TA

100 of S. typhimurium) as well as the sister chromatid exchange (SCE)-test (V79 cells) before and after UV-irradiation.

Based on results in Ames- and SCE-test a mutagenic activity was not obtained for all

L-phenylalanine samples, neither before nor after UV-irradiation.

 

The Ames-test was performed with 2 strains of S. typhimurium but not with strains of E. coli, too. The SCE-test as a different in vitro method with a different mode of action for determining genetic toxicity was performed in addition. The test results can be regarded as valid under these conditions.

 

In one supporting study it was also observed that L-phenylalanine did not show mutagenic

activity.

In another supporting study the results indicate that orally administered phenylalanine even

inhibits the development of gastric cancers.

 

The negative result for genetic toxicity was foreseeable as L-phenylalanine is a naturally occurring essential amino acid. L-phenylalanine is a normal constituent in living cells occurring as a free amino acid, bound to RNA and incorporated in proteins and peptides. It is ingested daily in significant amounts. Therefore human exposure through food is orders of magnitude higher than the anticipated levels of exposure from the uses covered by this dossier. L-phenylalanine is present in significant amounts in human body fluids – e. g. human blood plasma (Cynober 2002) - as well as in human cells. It is a basic metabolite and building block of all living organisms and therefore a genotoxic/mutagenic potential could be excluded.

 

Cynober L (2002): Plasma Amino Acid Levels With a Note on Membrane Transport: Characteristics, Regulation, and Metabolic Significance.Nutrition 18 (9), 761-766

Justification for selection of genetic toxicity endpoint

Key study

Justification for classification or non-classification