dialkyl-methyldihydro-heteropolycycle

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019-01-23 to 2019-02-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, München, Germany

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Test material form:

liquid

Method

Target gene:

His

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Metabolic activation system:

rat S9 liver microsomal fraction

Test concentrations with justification for top dose:

Experiment I:
0.0316, 0.100, 0.316, 1.0, 2.5 and 5.0 µL/plate
Experiment II:
0.0158, 0.050, 0.158, 0.50, 1.58 and 5.0 µL/plate

A correction factor of 1.015 was applied to consider the purity of the test item.

Vehicle / solvent:

ethanol

Controls

Controls 1

Untreated negative controls:

yes

Remarks:

aqua dest.

Negative solvent / vehicle controls:

yes

Remarks:

ethanol

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

methylmethanesulfonate

other: 4-nitro-o-phenylene-diamine

Remarks:

without metabolic activation

Controls 2

Untreated negative controls:

yes

Remarks:

aqua dest.

Negative solvent / vehicle controls:

yes

Remarks:

ethanol

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

with metabolic activation

Details on test system and experimental conditions:

TEST SYSTEM
Five strains of S. typhimurium with the following characteristics were used:
TA98: his D 3052; rfa-; uvrB-; R-factor: frame shift mutations
TA100: his G 46; rfa-; uvrB-; R-factor: base-pair substitutions
TA1535: his G 46; rfa-; uvrB-: base-pair substitutions
TA1537: his C 3076; rfa-; uvrB-: frame shift mutations
TA102: his G 428 (pAQ1); rfa-; R-factor: base-pair substitutions
Tester strains TA98, TA1535 and TA102 were obtained from MOLTOX, INC., NC 28607, USA. Tester strains TA100 and TA1537 were obtained from Xenometrix AG, Switzerland. They were stored as stock cultures in ampoules with nutrient broth (OXOID) supplemented with DMSO (approx. 8% v/v) over liquid nitrogen.

METHOD OF APPLICATION: in agar (plate incorporation)

EXPERIMENTAL PERFORMANCE
For the plate incorporation method the following materials were mixed in a test tube and poured over the surface of a minimal agar plate:
100 µL Test solution at each dose level, solvent control, negative control or reference mutagen solution (positive control),
500 µL S9 mix (for testing with metabolic activation) or S9 mix substitution buffer (for testing without metabolic activation),
100 µL Bacteria suspension (cf. Preparation of Bacteria, pre-culture of the strain),
2000 µL Overlay agar.
After solidification the plates were inverted and incubated at 37 °C for at least 48 h in the dark.

NUMBER OF REPLICATIONS: For each strain and dose level, including the controls, three plates were used.

DETERMINATION OF CYTOTOXICITY
Method: clearing or rather diminution of the background lawn or a reduction in the number of revertants down to a mutation factor of approximately ≤ 0.5 in relation to the solvent control

Evaluation criteria:

VALIDITY
A test is considered acceptable if for each strain:
- the bacteria demonstrate their typical responses to ampicillin (TA98, TA100, TA102)
- the negative control plates (A. dest.) with and without S9 mix are within the historical control data ranges
- corresponding background growth on negative control, solvent 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 analysable

MUTAGENICITY
The Mutation Factor is calculated by dividing the mean value of the revertant counts through 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.

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.

Results and discussion

Test results

Key result

Species / strain:

S. typhimurium, other: TA98, TA100, TA1535, TA1537 and TA102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

True negative controls validity:

not applicable

Positive controls validity:

valid

Any other information on results incl. tables

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 the test item at any concentration level, neither in the presence nor absence of metabolic activation in experiment I and II.

All criteria of validity were met.

Applicant's summary and conclusion

Conclusions:

The test item is considered to be non-mutagenic in this bacterial reverse mutation assay.

Executive summary:

In order to investigate the potential of the test item for its ability to induce gene mutations the plate incorporation test (experiment I and II) was performed with the Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and TA102.

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:

Experiment I:

0.0316, 0.100, 0.316, 1.0, 2.5 and 5.0 μL/plate

Experiment II:

0.0158, 0.050, 0.158, 0.50, 1.58 and 5.0 μL/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 the test item at any concentration level, neither in the presence nor absence of metabolic activation in experiment I and II.

All criteria of validity were met.

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used.

Therefore, the test item is considered to be non-mutagenic in this bacterial reverse mutation assay.