Estr-5(10)-en-3-one, 17-hydroxy-, (17.beta.)-

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation (bacterial reverse mutation assay / Ames test): positive [Reimann/Jarzombek 2006]

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:

Jul 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

Histidine gene locus; tryptophan gene locus

Species / strain / cell type:

S. typhimurium, other: TA 1535, TA 100, TA 1537, TA 1538 and TA 98

Additional strain / cell type characteristics:

not applicable

Species / strain / cell type:

E. coli WP2 uvr A

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced male Sprague-Dawley rat liver S9 mix

Test concentrations with justification for top dose:

0.05, 0.1, 0.25, 0.5, 1.0, 2.5 and 5.0 mg/plate
The highest dose tested should cause toxicity (thinning of the background lawn of bacteria) or should correspond to the substance's precipitation range (visible precipitates on the plates) but should not exceed 5 mg/plate or 5 μL/plate.

Vehicle / solvent:

DMSO

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

sodium azide

benzo(a)pyrene

cyclophosphamide

ethylmethanesulphonate

other: 4-Nitro-o-phenylenediamine, N-Methyl-N’-nitro-N-nitrosoguanidine, Anthracene-2-amine

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: ca. 72 hours (S. typhimurium) and ca. 48 hours (E. coli)

- all plates were prepared in triplicates

Evaluation criteria:

A positive response was considered if the number of revertants of the compound groups compared to the number of revertants of the negative group was reproducibly higher than 2-fold. A dose-dependent increase in the number of revertants was also considered to indicate a mutagenic effect.

Statistics:

The arithmetic means of the number of mutant colonies of the 3 parallel plates in the negative control groups were compared with those of the compound groups.

Species / strain:

S. typhimurium, other: TA1535, TA100, TA1537, TA1538 and TA98

Metabolic activation:

without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Growth inhibition of the background lawn was observed in all tester strains from 1.0 mg per plate onwards without metabolic activation.

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium, other: TA1535, TA100, TA1538 and TA98

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Growth inhibition of the background lawn was observed from 2.5 mg per plate onwards.

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Growth inhibition of the background lawn was observed in all tester strains from 1.0 mg per plate onwards without metabolic activation.

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

Precipitates in the agar were found from 1.0 mg/plate onwards.

All S. typhimurium strains used (TA1535, TA100, TA1537, TA1538 and TA98) showed increased reversion to prototrophy when incubated with the test substance at doses between 0.1 and 5.0 mg/plate in the absence of metabolic activation. The experiments with S9 mix gave exclusively negative results.

The Escherichia coli strain used (WP2uvrA) did not show increased reversion to prototrophy with the test substance at any doses tested in the absence or in the presence of S9 mix.

Executive summary:

In conclusion it can be stated that under the experimental conditions reported, the test substance induced gene mutations by base-pair changes or frame-shifts in the genome of the S. typhimurium strains used, when tested up to highest recommended dose level of 5.0 mg/plate in the absence of S9 mix. Therefore, the test substance has to be considered as directly mutagenic in the Ames test.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In conclusion it can be stated that under the experimental conditions reported, the test substance induced gene mutations by base-pair changes or frame-shifts in the genome of the S. typhimurium strains used, when tested up to highest recommended dose level of 5.0 mg/plate in the absence of S9 mix. Therefore, the test substance has to be considered as directly mutagenic in the Ames test. [Reimann/Jarzombek 2006]

Justification for classification or non-classification

Based on the available information (restricted to one in vitro study detecting gene mutations in bacteria) a classification according to Regulation (EC) No. 1272/2008 (CLP) is not required although the test result is positive.