Imidazole

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was performed according to OECD TG 471 and GLP; E.coli WP2 uvrA, E. coli WP2 uvrA (pKM101) or S. typhimurium TA 102 was not included

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

(adopted 26-May-1983)

Deviations:

yes

Remarks:

E.coli WP2 uvrA, E. coli WP2 uvrA (pKM101) or S. typhimurium TA 102 was not included

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Imidazole

EC Number:

206-019-2

EC Name:

Imidazole

Cas Number:

288-32-4

Molecular formula:

C3H4N2

IUPAC Name:

1H-imidazole

Details on test material:

Imidazole (CAS: 288-32-4), purity 99.9%

Method

Target gene:

histidine operon

Species / strain

Species / strain / cell type:

other: Salmonella typhimurium TA1535, TA100, TA1537, TA98

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

S-9 mix from rat liver after i.p. treatment with 500 mg Aroclor (20% solution in peanut oil-w/v).

Test concentrations with justification for top dose:

Doses:
1st experiment:
standard plate test 0, 20, 100, 500, 2500, 5000 µg/plate tested with all tester strains. Solvent was aqua dest.
3 plates per dose and control.

2nd experiment:
preincubation test 0, 20, 100, 500, 2500, 5000 µg/plate tested with all tester strains. 3 plates per dose and control.

Vehicle / solvent:

Complete solubility of TS in aqua dest. was given.

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: +S9: 2-aminoanthracene (all strains); -S9: MNNG (TA 100, TA 1535), 4-nitrophenylenediamine (TA 98), 9-aminoacridine chloride monohydrate (TA 1537)

Details on test system and experimental conditions:

TEST SYSTEM
Base pair substitution (TA 1535, TA 100) and frameshift (TA1537, TA 98) tester strains with and without metabolic activation.
Standard plate test (according to Ames et al.) and preincubation test (according to Matsushima et al.) were performed. In the standard
plate test, 0.1 ml of bacteria suspension (1E+06 bacteria/ml) is given to 2 ml of soft agar containing 0.5 mM histidine; 0.1 ml of test solution and 0.5 ml of S9 mix (or phosphate buffer) is added, mixed and poured onto minimal glucose agar plates. After incubation at 37°C for
48 hrs in the dark, the number of his+-revertants is counted. The preincubation test differs in that bacteria are preincubated with S9 mix
and the test substance solution at 37°C for 20 min prior to mixing with soft agar and incubation on the agar plates.

Negative control:
Parallel with each experiment with and without S-9 mix, a negative control (solvent control, sterility control) is carried out for each tester
strain in order to determine the spontaneous mutation rate.

Positive controls:
The following positive control substances are used to check the mutability of the bacteria and the activity of the S-9 mix:

with S-9 mix:
2.5 µg and 10 ug 2-aminoanthracene (2-AA) (dissolved in DMSO) for the strains TA 100, TA 98, TA 1537 and TA 1535

without S-9 mix:
5 µg N-methyl-N-nitro-N-nitrosoguanidine (MNNG) (dissolved in DMSO) for the strains TA 100 and TA 1535
10 µg 4-nitro-o-phenylendiamine (NPD) (dissolved in DMSO) for the strain TA 98
100 µg 9-aminoacridine chloride monohydrate (AAC) (dissolved in DMSO) for the strain TA 1537 .

Evaluation criteria:

Reaction to a substance is regarded as positive if all of the following criteria are met
- doubling of spontaneous control mutation rate
- dose-response relationship
- reproducibility of results

Statistics:

mean and standard deviation from 3 plates/concentration were calculated

Results and discussion

Test results

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: imidazole has no influence on the pH value of the medium
- Water solubility: soluble in water at all concentrations tested
- Precipitation: no precipitation occured
- Other confounding effects: none

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

No bacteriotoxic effect (reduced His-background growth) was noted. No increase of revertants was seen in the standard plate or preincubation test, with or without S9 mix, in any tester strain. The mean revertant increase by positive control substances was as expected.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

Executive summary:

Imidazole was tested in the standard Ames test and in the preincubation Ames test conducted under GLP and according to the OECD TG 471. The substance was tested with Salmonella typhimurium TA 1535, TA 100, TA 1537, and TA 98 both in the presence and absence of metabolic activation in concentrations up to 5000 μg/plate. No mutagenic or bacteriotoxic effect was noted.