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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

A number of tests are available that assess the potential of L-Tyrosine to cause genetic toxicity.

The key study is a recent Ames test in accordance with OECD and GLP criteria.

Additionally, a number of supporting studies were found in the published literature. It concerns two gene mutation tests in bacteria (a WP2 Mutoxitest and a Lac+ mutagenesis test), and two chromosome aberration type tests (a Sister Chromatic Exchange test and a DAU-DNA alkaline unwinding test).

All tests were found to be negative. Hence, L-Tyrosine is not genotoxic.

Link to relevant study records
Reference
Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
28.07. - 24.09.2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
21st July, 1997
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
May 30, 2008
Qualifier:
according to
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Version / remarks:
August 1998
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay
Test material information:
Composition 1
Specific details on test material used for the study:
purity: 99.9%
Target gene:
histidine
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102
Metabolic activation:
with and without
Metabolic activation system:
Mammalian Microsomal Fraction S9 Mix
Test concentrations with justification for top dose:
31.6, 100, 316, 1000, 2500 and 5000 μg/plate

- no precipitation of the test item was observed in any tester strain used in experiment I and II (with
and without metabolic activation)
- no toxic effects of the test item were noted in any of the five tester strains used up to the highest
dose group evaluated (with and without metabolic activation) in experiment I and II
Vehicle:
DMSO
Negative controls:
yes
Remarks:
DMSO
Positive controls:
yes
Remarks:
Without metabolic activation
Positive control substance:
sodium azide
methylmethanesulfonate
other: 4-NOPD; 4-nitro-o-phenylene-diamine
Positive controls:
yes
Positive control substance:
other: 2-AA; 2-aminoanthracene
Remarks:
With metabolic activation
Details on test system and conditions:
METHOD OF APPLICATION:
in agar (plate incorporation) in Experiment I and pre-incubation in
Experiment II.

DURATION
- Exposure duration: 48h at 37°C

NUMBER OF REPLICATIONS: 3

ACCEPTANCE CRITERIA:
A test is considered acceptable if for each strain:
- the bacteria demonstrate their typical responses to ampicillin (TA 98, TA 100 and TA 102)
- the negative control plates (A. dest.) with and without S9 mix are within the historical control data
range of the test facility
- corresponding background growth on solvent control, negative control and test plates is observed.
- the positive controls show a distinct enhancement of revertant rates over the control plate
- at least five different concentrations of each tester strain are analyzable
Rationale for test conditions:
these are according to the OECD guideline 471
Evaluation criteria:
The Mutation Factor is calculated by dividing the mean value of the revertant counts by the mean
values of the solvent control (the exact and not the rounded values are used for calculation).

A test item is considered as mutagenic if:
- a clear and dose-related increase in the number of revertants occurs and/or
- a biologically relevant positive response for at least one of the dose groups occurs
in at least one tester strain with or without metabolic activation.
A biologically relevant increase is described as follows:
- if in tester strains TA 98, TA 100 and TA 102 the number of reversions is at least twice as high
- if in tester strains TA 1535 and TA 1537 the number of reversions is at least three times higher
than the reversion rate of the solvent control.

According to OECD guidelines, the biological relevance of the results is the criterion for the
interpretation of results, a statistical evaluation of the results is not regarded as necessary.

A test item producing neither a dose related increase in the number of revertants nor a reproducible
biologically relevant positive response at any of the dose groups is considered to be non-mutagenic
in this system.
Statistics:
According to OECD guidelines, the biological relevance of the results is the criterion for the
interpretation of results, a statistical evaluation of the results is not regarded as necessary.
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Negative controls valid:
yes
Positive controls valid:
yes
Remarks on result:
other: not mutagenic
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Negative controls valid:
yes
Positive controls valid:
yes
Remarks on result:
other: not mutagenic
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Negative controls valid:
yes
Positive controls valid:
yes
Remarks on result:
other: not mutagenic
Key result
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Negative controls valid:
yes
Positive controls valid:
yes
Remarks on result:
other: not mutagenic
Key result
Species / strain:
S. typhimurium TA 102
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
no
Negative controls valid:
yes
Positive controls valid:
yes
Remarks on result:
other: not mutagenic
Additional information on results:
- no precipitation of the test item was observed in any tester strain used in experiment I and II (with
and without metabolic activation)

- no toxic effects of the test item were noted in any of the five tester strains used up to the highest
dose group evaluated (with and without metabolic activation) in experiment I and II
Conclusions:
In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, L-Tyrosine did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used. Therefore, L-Tyrosine is considered to be non-mutagenic in this bacterial reverse mutation assay.
Executive summary:

In the current study the potential of the test item L-Tyrosine to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II) using Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and TA 102 was assessed according to OECD TG 471 and in compliance to GLP.

In two independent experiments several concentrations of the test item were used. Each assay was conducted with and without metabolic activation. The concentrations, including the controls, were tested in triplicate. The following concentrations of the test item were prepared and used in the experiments: 31.6, 100, 316, 1000, 2500 and 5000 μg/plate

No precipitation of the test item was observed in any tester strain used in experiment I and II (with and without metabolic activation).

No toxic effects of the test item were noted in any of the five tester strains used up to the highest dose group evaluated with and without metabolic activation in experiment I and II.

No biologically relevant increases in revertant colony numbers of any of the five tester strains were observed following treatment with L-Tyrosine at any concentration level, neither in the presence nor absence of metabolic activation in experiment I and II.

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, L-Tyrosine did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used. Therefore, L-Tyrosine is considered to be non-mutagenic in this bacterial reverse mutation assay.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Justification for classification or non-classification

As all in-vitro tests are negative, classification of L-tyrosine for this endpoint is not required.