Norethisterone

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference

Reference Type:

publication

Title:

Studies for a Genotoxic Potential of Some Endogenous and Exogenous Sex Steroids. 1. Communication: Examination for the Induction of Gene Mutations Using the Ames Salmonella/Microsome Test and the HGPRT Test in V79 Cells

Author:

Lang R and Reimann R

Year:

1993

Bibliographic source:

Environmental and Molecular Mutagenesis 21, 272-304

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

GLP compliance:

not specified

Type of assay:

mammalian cell gene mutation assay

Test material

Test material information

Method

Target gene:

HPRT

Species / strain

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Details on mammalian cell type (if applicable):

supplied by Prof. Miltenburger, Darmstadt, Germany

Metabolic activation:

with and without

Metabolic activation system:

From male Sprague-Dawley rats pretreated with Aroclor 1254 (purchased from Organon Teknika Co. (Durham, NC))

Test concentrations with justification for top dose:

At least four concentrations of the test substance without and with S9 mix are scored for mutant colonies. The highest dose chosen for evaluation should be clearly toxic, i.e.. it should cause a reduction of the plating efficiency (cell surviva]) or correspond to the substance's solubility limit (precipitates in the culture). Nontoxic compounds will be tested up to 10-² M or 5-10 mg/ml.- (in the absence or presence of liver cells).

Vehicle / solvent:

DMSO or aceton

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

no

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: EMS, MNNG (without metabolic activation); DMBA (with S9 mix)

Evaluation criteria:

So far. no satisfactory mathematical methods are available for statistical analysis of mammalian cell mutagenicity experiments such as those performed here. Our experience has shown that the following predetermined descriptive criteria are the most useful for interpretation of the results. An evaluation is made only after a repeat experiment has been carried out. The evaluation of the results is performed as follows: (1)the test substance is classified as mutagenic if it induces with one of the test substance concentrations, reproducibly, a mutation frequency that is three times higher than the spontaneous mutant frequency in this experiment; (2) the test substance is classified as mutagenic if there is a reproducible concentration-related increase in the mutation frequency;
such an evaluation may be considered independently of the enhancement factor for induced mutants; however, in a case-by-case evaluation both decisions depend on the level of the corresponding negative control data. If there is by chance a low spontaneous mutation rate as compared to the range found in this laboratory, a seemingly concentrationrelated increase in the mutations or a factor of three or even more within this range may be regarded as being irrelevant.
When considerable variations in the results occur, clarificationis sought in additional experiments.

Results and discussion

Test results

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

The mutagenicity results and data of nine progestins (cyproterone acetate, dehydrospirorenone, gestodene, gestonorone caproate, levonorgestrel, norethisterone, norethisterone acetate, norethisterone enanthate, norethynodrel) are reported. All sex steroids were investigated using the Ames Test and two sex steroids were also studied in the HPRT test with V79 cells. For all assays evaluation of the data indicates that any of the progestins was able to induce gene mutations wether in the absence or the presence of S9 mix. On the basis of these findings, it seems justifiable to extrapolate that sex steroids in general possess obviously no mutagenic potential detectable in gene-mutation assays in vitro.

Remarks on result:

other:

Remarks:

The mutagenicity results and data of 17 sex steroids are reported. Nine of them are progestins (cyproterone acetate, dehydrospirorenone, gestodene, gestonorone caproate, levonorgestrel, norethisterone, norethisterone acetate, norethisterone enanthate, norethynodrel). All progestogenic steroid hormones were investigated using the Ames Test and two of them (Cyproterone Acetate; Dehydrospirorenone) were also studied in the HPRT test with V79 cells. For all assays evaluation of the data indicates that any of the progestins was able to induce gene mutations wether in the absence or the presence of S9 mix. On the basis of these findings, it seems justifiable to extrapolate that sex steroids in general possess obviously no mutagenic potential detectable in gene-mutation assays in vitro.

Applicant's summary and conclusion

Conclusions:

The mutagenicity results and data of nine progestins (cyproterone acetate, dehydrospirorenone, gestodene, gestonorone caproate, levonorgestrel, norethisterone, norethisterone acetate, norethisterone enanthate, norethynodrel) are reported. All sex steroids were investigated using the Ames Test and two sex steroids were also studied in the HPRT test with V79 cells. For all assays evaluation of the data indicates that any of the progestins was able to induce gene mutations wether in the absence or the presence of S9 mix. On the basis of these findings, it seems justifiable to extrapolate that sex steroids in general possess obviously no mutagenic potential detectable in gene-mutation assays in vitro.

Executive summary:

2 of 9 progestins did not induce substantial and reproducible dose dependent increase of the mutation frequency in a mammalian cell gene mutation assay (HPRT) according to OECD TG 476. Appropriate reference mutagens, used as positive controls, induced a distinct increase in mutant colonies and thus, showed the sensitivity of the test system and the activity of the metabolic activation system. Therefore, the substances were considered to be non-mutagenic in the specified test.