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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Key study: The test substance resulted to be non mutagenic to the tester strains with and without metabolic activation in Ames test.

Supporting study: Test substance was negative with respect to genotoxicity in the DNA repair test with hepatocytes for both species (rat and mice) and also had the negative results in mutagenicity in Salmonella Typhymurrium test.

Link to relevant study records

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Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Reference:
Composition 0
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Principles of method if other than guideline:
Ames et al.
GLP compliance:
not specified
Type of assay:
bacterial reverse mutation assay
Test material information:
Composition 1
Target gene:
Histidine-requiring gene
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Test concentrations with justification for top dose:
1,600, 1,200, 800, 400, 200, 100 μg / 0.1 ml / Plate
Vehicle:
- Vehicle(s)/solvent(s) used: water
Details on test system and conditions:
METHOD OF APPLICATION: in agar (plate incorporation).

DURATION
- Preincubation period:20 min
- Exposure duration:48 hours, 37ºC
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
not specified
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
not specified
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity:
not specified
Conclusions:
The test substance thiosemicarabzide was not mutagenic in the strains TA100; TA1535 and TA98 of S. typhimurium with and without metabolic activation.
Executive summary:

A bacterial mutagenicity assay was performed for the test item Thiosemicarbazide in strains TA100, TA1535 and TA98 of S. typhimurium. The test item dilutions were prepared in water: 1,600, 1,200, 800, 400, 200, 100 μg / 0.1 ml / Plate. Plates were incubated at 37ºC for 48-72h and after this period colonies were counted. The test substance resulted to be non mutagenic to the tester strains with and without metabolic activation.

Endpoint:
in vitro DNA damage and/or repair study
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
significant methodological deficiencies
Remarks:
Insuficient data for assessment. No GLP, NO guideline followed
Reference:
Composition 0
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 482 (Genetic Toxicology: DNA Damage and Repair, Unscheduled DNA Synthesis in Mammalian Cells In Vitro)
Deviations:
no
GLP compliance:
no
Type of assay:
other: Hepatocyte/DNA repair test
Test material information:
Composition 1
Species / strain:
hepatocytes: Rat and mouse
Details on mammalian cell lines (if applicable):
CELLS USED
- Source of cells:isolated from the liver of rats (ACI/N) weighting 200 -250 g and from liver of mice (C3H/HeN) weighing 20 g

MEDIA USED
- Type and identity of media including CO2 concentration if applicable:William´s medium E
Additional strain characteristics:
not specified
Test concentrations with justification for top dose:
0.001,0.0001,0.00001,0.000001 and 0.0000001 M
Vehicle:
- Vehicle(s)/solvent(s) used: distilled water
Solvent controls:
yes
Positive controls:
yes
Positive control substance:
9,10-dimethylbenzanthracene
other: N-2fluorenylacetoamide
Details on test system and conditions:
METHOD OF APPLICATION: in medium-Williams Medium E.

DURATION
- Exposure duration: 20 hours
- Selection time (if incubation with a selection agent): 14 days

NUMBER OF REPLICATIONS:2

NUMBER OF CELLS EVALUATED:50 cells / coverslips

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; cloning efficiency; relative total growth.
Evaluation criteria:
Each cell nucleus was positive when the net nuclear grain count was more than 5 grains above the cytopasmic background.
Test substance was considered positive when the mean nuclear grain count was more than 5 grains or positive cells were more tna 33%.
Statistics:
Autoradiographic grains weere counted on a CRT display (Olympus type S) with microscopic attachment.
Key result
Species / strain:
hepatocytes: Rat or mice
Metabolic activation:
not specified
Genotoxicity:
negative
Vehicle controls valid:
yes
Positive controls valid:
yes

Tabel No.1: Result of DNA repair test of thiosemicarbazide

Chemical

Dose (M)

Rat

Mouse

 

 

UDS grains/nucleus

DNA repair

UDS grains/nucleus

DNA repair

 

Thiosemicarbazide

10-3

-1.0+-1.5

 

      -

-0.7+-1.2

 

-

10-4

-1.2+-1.4

-0.7+-1.4

10-5

-0.8+-1.3

-0.7+-1.5

Repair response was not present in 2 doses (10-6 and 10-7)

Conclusions:
Test substance was negative with respect to genotoxicity in the DNA repair test with hepatocytes for both species (rat and mice) and also had the negative results in mutagenicity in Salmonella Typhymurrium test.
Executive summary:

In the present study, thiosemicarbazide was tested to genotoxicity in the DNA repair test with hepatocytes from rats and mices. As medium was used Williams Medium E. After hepatocytes were isolated, they were attached to plastic coverslips in primary culture for 2 hours using Williams Medium E. Then were washed and exposed to the test compunds for 20 hours. Test item was dilluted with distilled water before addition to the cultures (10-3 and 10-7 M). Concentration tested included the highest soluble non toxic dose. At the end of incubation, the cultures were washed in medium and the coverslips were mounted on glass sides which were dipped in Sakura NR-M2 photographic emulsions and exposed for 14 days. In the cocnentration of 10-6 and 10 -7 DNA reponse was not presented. Based on the results obtained from that study, test substance is negative with respect to genotoxicity in the DNA repair test with hepatocytes for both species (rat and mice).

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

Genetic toxicity in vivo

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Key study: A bacterial mutagenicity assay was performed for the test item Thiosemicarbazide in strains TA100, TA1535 and TA98 of S. typhimurium. The test substance resulted to be non mutagenic to the tester strains with and without metabolic activation.

Supporting study: In the present study, thiosemicarbazide was tested to genotoxicity in the DNA repair test with hepatocytes from rats and mices in accordance with the methods of Williams et al. The cultures were exposed to test compound at 10-3, 10-4, 10-5, 10-6 and 10 -7 doses. In the concentration of 10-6 and 10-7 DNA reponse was not presented.As medium was used Williams Medium E. Based on the results obtained from that study, test substance is negative with respect to genotoxicity in the DNA repair test with hepatocytes for both species (rat and mice).

Justification for classification or non-classification

Based on available data from the key and supporting study, Thiosemicarbazide is not classified for germ cel mutagenicity according to CLP Regulation no. 1272/2008.