Paraquat-dichloride

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

No E. coli or TA 102 tested

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1977

Report date:

1977

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

no E. coli or TA 102 strain tested; TA 1538 was used instead of 1537

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Paraquat-dichloride

EC Number:

217-615-7

EC Name:

Paraquat-dichloride

Cas Number:

1910-42-5

Molecular formula:

C12H14N2.2Cl

IUPAC Name:

1,1’-dimethyl-4,4’-bipyridyldiylium dichloride

Method

Target gene:

His-locus

Species / strain

Species / strain / cell type:

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

Metabolic activation:

with and without

Metabolic activation system:

Aroclor or phenobarbital induced rat liver S9-mix

Test concentrations with justification for top dose:

TEST CONCENTRATIONS
0.16, 0.8, 4, 20, 100, 500, 2500, 5000 µg/plate

JUSTIFICATION FOR TOP DOSE
- The tope dose was 5000 μg/plate which is the standard limit concentration recommended in the OECD TG 471. This study has been conducted following principles similar to OECD 471.

Vehicle / solvent:

VEHICLE
- water

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Remarks:

DMSO was used as vehicle for the positive control compound

Positive control substance:

2-acetylaminofluorene

2-nitrofluorene

other: 2-(1-chloro-2-isopropylaminoethyl) naphthalene (CPE); Meclorethanine

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar plate incorporation
- Top agar consisted of 0.6% agar and 0.5% NaCl. Before use 100 mL of top agar was mixed with 10 mL of a solution of 0.5 mM L-histidine HCl and .5 mM biotin.
- Petri plates (9 cm diameter) poured with 30 mL Vogel-Bonner minimal medium with 1.5 % Bacto-Difco agar and 2% glucose.

EXPERIMENTAL PROCEDURE
0.1 mL of an overnight nutrient broth culture of the bacterial tester strain, 0.1 mL of varying concentrations of the test substance and 0.15 or 0.5 mL of S-9 mix were added to 2 mL of molten agar at 45 °C. The top agar was distributed uniformly over the minimal glucose agar plates and allowed to harden before incubation.

DURATION
- Exposure duration: 48 to 72 hours at 37°C

NUMBER OF REPLICATIONS:
- Triplicates for TA 1535 and TA 1538
- Duplicates for the remaining strains

DETERMINATION OF CYTOTOXICITY
- Method: reduction in mean revertant colony counts

Evaluation criteria:

Not specified in the document

Results and discussion

Test results

Key result

Species / strain:

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

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

CYTOXICITY
A toxic response was demonstrated at some of the higher concentrations which showed that the compound was entering the bacteria.

Applicant's summary and conclusion

Conclusions:

This Ames study indicates that the test substance has no mutagenic activity with or without metabolic activation.

Executive summary:

The test substance was assayed in the Salmonella typhimurium mutagenicity plate incorporation assay (equivalent to OECD TG 471) and it was not mutagenic. On many occasions the compound was tested using TA 1535 and TA 1538 strains with and without the presence of rat liver post-mitochondrial supernatant (PMS) with cofactor (S-9 mix) from rats administered phenobarbital. It was also tested using the TA 1535, TA 1538, TA 98 and TA 100 strains with S-9 mix made from rats administered Aroclor, with PMS but without cofactor and also without S-9 mix. A concentration range was used between 0.16 - 5000 µg of the test material per plate to maximise the chance of producing an effect. In all cases, there were no biologically significant increases above solvent control levels. The lack of effect was not due to the insensitivity of the system used, since a positive response was clearly demonstrated with the positive control compounds.