thiourea; thiocarbamide

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021-04-20 - 2023-04-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2023

Report date:

2023

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test using the Hprt and xprt genes)

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian cell gene mutation test using the Hprt and xprt genes

Test material

Test material information

Constituent 1

Reference substance name:

Thiourea

EC Number:

200-543-5

EC Name:

Thiourea

Cas Number:

62-56-6

Molecular formula:

CH4N2S

IUPAC Name:

thiourea

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

Batch: 021701
Retest: 2023-08-04
Purity: 100.1 %

Method

Target gene:

HPRT-Gene

Species / strain

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Metabolic activation system:

Mammalian Microsomal Fraction S9 Mix

Test concentrations with justification for top dose:

Experiment I without metabolic activation: 1.25, 2.5, 5, 7.5, 10 mM
Experiment I with metabolic activation: 1.25, 2.5, 5, 7.5, 10 mM
Experiment II with metabolic activation: 2, 4, 6, 8, 10 mM

No precipitation of the solved test item was noted in any experiment.
No growth inhibition (relative survival < 70%) was observed in any experiments.

Vehicle / solvent:

Culture Medium

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

no

Positive controls:

yes

Positive control substance:

7,12-dimethylbenzanthracene

ethylmethanesulphonate

Details on test system and experimental conditions:

Complete Culture Medium: MEM +
10 % FBS
100 U Penicillin / 100 µg/ml strepptomycin
2 mM L-glutamin
25 mM HEPES
2.5 µg/ml amphotericin B

Treatment Medium: MEM supplemented as above w/o FBS

Cells incubated at 37 °C and 5 % CO2

Statistics:

non-parametric Mann-Whitney test

Results and discussion

Test results

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

True negative controls validity:

not specified

Positive controls validity:

valid

Applicant's summary and conclusion

Conclusions:

In conclusion, in the described mutagenicity test under the experimental conditions reported, the test item Thiourea is considered to be non-mutagenic at the HPRT locus using V79 cells of the Chinese Hamster.

Executive summary:

The test substance Thiourea was assessed for its potential to induce mutations at the HPRT locus using V79 cells of the Chinese Hamster.

The solved test substance was incubated with cells for 4 hours. The main experiments were performed independently with and without metabolic activation.

The concentrations used in the main experiments were selected based on data from the pre-experiments.

 

The test item was investigated at the following concentrations:

Main Experiment without metabolic activation:       1.25, 2.5, 5, 7.5, 10 mM

Main Experiment I with metabolic activation:               1.25, 2.5, 5, 7.5, 10 mM

Main Experiment II with metabolic activation:              2, 4, 6, 8, 10 mM

 

No precipitation of the solved test item was noted in any experiment.

No growth inhibition (relative survival < 70%) was observed in any experiments.

 

In the experiment without metabolic activation at concentrations 1.25 and 2.5 mM the Upper Control Limit of 47.4 was exceeded with mutant frequency values of 49.39 and 61.79, respectively. However, at higher concentrations up to the recommended maximum concentration of 10 mM no increase of mutant frequency values was observed. With 61.79 at 2.5 mM a statistical analysis displayed that the mutant frequency was significantly increased over those of the negative control. Nevertheless, the c² test for trend did not show a concentration-related increase of mutant frequencies. Therefore, no importance was attributed to both concentrations.

 

In the experiment I with metabolic activation at concentration 10 mM the Upper Control Limit of 51.6 was exceeded with mutant frequency values of 51.88. However, a statistical analysis displayed that the mutant frequency was significantly increased over those of the negative control. Nevertheless, the c² test for trend did show a concentration-related increase of mutant frequencies. Therefore, a confirmatory experiment with metabolic activation was performed.

 

In the experiment II with metabolic activation all mutant frequency values were within the historical control data. A statistical analysis displayed that there is no significant increase of mutant frequencies over those of the negative control. Furthermore, the c² test for trend did not show a concentration-related increase of mutant frequencies.

 

DMBA and EMS were used as positive controls and showed distinct and biologically relevant effects in mutation frequency.