Rhodium triiodide

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:

Study commenced 28-Apr-2006. Study completed 19-May-2006.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study, to GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Rhodium (III) iodide

Cas Number:

15492-38-3

IUPAC Name:

Rhodium (III) iodide

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report): Rhodiumtrijodide [sic]
- Substance type: No data
- Physical state: Black powder
- Analytical purity: Rhodium=20.59%
- Impurities (identity and concentrations): Sulfur <0.4%, Sum of free bromide-chloride=<0.1% (values in percent based on mass)
- Composition of test material, percentage of components: No data
- Isomers composition: No data
- Purity test date: 07.02.2006
- Lot/batch No.: 4305/00-06
- Expiration date of the lot/batch: No data
- Stability under test conditions: No data
- Storage condition of test material: room temperature
- Other: 2.5 g Received from Umicor on 10-Feb-2006. Container: colourless glass bottle. TRC reference number: 10009.

Method

Target gene:

Histidine

Species / strain

Species / strain / cell type:

bacteria, other: S. typhimurium TA 1535, TA 1537, TA 98 and TA 100, E. coli WP2 uvr A

Details on mammalian cell type (if applicable):

not applicable

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital/betanaphthoflavone-induced rat liver S9

Test concentrations with justification for top dose:

313, 625, 1250, 2500 and 5000 µg/plate.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: [DMSO]
- Justification for choice of solvent/vehicle: Solubility of test item was evaluated in a preliminary trial, using sterile distilled water, DMSO, ethanol and acetone. These solvents were reportedly chosen due to compatibility with the survival of the bacteria and the S9 metabolic activity. DMSO was selected as it produced homogeneous suspensions of up to 100 mg/ml, permitting a maximum concentration of 5000 µg/plate to be used.

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

yes

Positive controls:

yes

Positive control substance:

other: methylmethanesulfonate; sodium azide; 2-nitrofluorene; 9-aminoacridine; 2-aminoanthracene

Remarks:

Appropriate strain-specific positive and negative controls were used. Historical data for untreated and positive controls were provided for plate incorporation and pre-incubation methods, both with and without metabolic activation.

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation) (experiment 1)

DURATION
- Exposure duration: 72 hours

NUMBER OF REPLICATIONS: 3

DETERMINATION OF CYTOTOXICITY
- Toxicity was assessed in a preliminary toxicity test: based on decline of spontaneous revertants, a thinning of the background lawn or a microcolony formation.

METHOD OF APPLICATION: preincubation; in suspension (experiment 2)

DURATION
- Preincubation period: 30 minutes
- Exposure duration: 72 hours

NUMBER OF REPLICATIONS: 3

DETERMINATION OF CYTOTOXICITY
- Toxicity was assessed in a preliminary toxicity test: based on decline of spontaneous revertants, a thinning of the background lawn or a microcolony formation.

Evaluation criteria:

After incubation, numbers of revertant colonies were counted. The following findings were required for the test item to be considered mutagenic: two-fold (or more) increases in mean revertant numbers, observed at two consecutive dose-levels or at the highest achievable dose-level only; with evidence of a dose-response relationship showing increasing numbers of mutant colonies with increasing dose-levels.

Statistics:

Individual plate counts for each experiment are given together with the means and standard errors of the means, and regression analyses (least squares method). The regression line included the solvent control data, and not the untreated control data. The correlation co-efficient (r), the value of students “t” statistic, and the p-value for the regression lines are also given.

The study report states that “evaluation of Ames test data based on a ‘doubling rate’ has been shown to be as effective as statistical techniques in allowing the correct interpretation of test results”. A supporting reference is listed.

Results and discussion

Test results

Test results 1

Species / strain:

S. typhimurium, other: TA 98; TA 100

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 2

Species / strain:

bacteria, other: S. typhimurium TA 1535; TA 1537; E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 3

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 4

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 5

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 6

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

without

Genotoxicity:

ambiguous

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: no data
- Effects of osmolality: no data
- Evaporation from medium: no data
- Water solubility: The test item was not sufficiently soluble in sterile distilled water according to the report.
- Precipitation: Precipitation of the test item was observed at the highest test concentration. This did not interfere with scoring according to the report.
- Other confounding effects: No data.

RANGE-FINDING/SCREENING STUDIES: No data.

COMPARISON WITH HISTORICAL CONTROL DATA:

ADDITIONAL INFORMATION ON CYTOTOXICITY: No toxicity was observed at any of the dose levels (50, 158, 500, 1580 and 5000 µg/plate) tested in the presence or absence of S9 metabolism. Toxicity was assessed on the basis of a decline in the number of revertants, a thinning of the background lawn or a microcolony formation.

Remarks on result:

other: other: plate incorporation method

Remarks:

Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
positive S. typhimurium TA 98, TA 100, TA 1537
negative with metabolic activation S. typhimurium TA 1535
positive without metabolic activation S. typhimurium TA 1535
ambiguous without metabolic activation E. coli WP2 uvrA

In a guideline study, to GLP, rhodiumtrijodide was mutagenic in Salmonella typhimurium strains TA 98, TA 100 and TA 1537, when tested in the absence and presence of a rat liver metabolic activation system (S9), as well as in strain TA 1535 in the absence of S9. In Escherichia coli WP2uvrA, an ambiguous result was seen in the absence of S9.

Executive summary:

In an OECD Test Guideline 471 study, conducted according to GLP, rhodiumtrijodide was examined for the ability to induce gene mutations in Salmonella typhimurium (strains TA 1535, TA 1537, TA 98, and TA 100) and Escherichia coli (WP2uvrA) in the presence and absence of phenobarbital/betanaphthoflavone-induced rat liver metabolic activation system (S9). A preliminary solubility trial identified dimethylsulphoxide (DMSO) as a suitable solvent for the test material. An initial experiment (in triplicate) was conducted for each strain using the plate incorporation method, involving concentrations of up to 5000 µg/plate, based on observed precipitation (in DMSO) in the preliminary trial.

 

Large increases in the number of revertant colonies were observed in strains TA 98 and TA 100, in both the presence and absence of S9 when the plate incorporation method was used. Further testing of the remaining strains using the pre-incubation method (also in triplicate) revealed small, but significant and dose-related increases in TA 1535 in the absence of S9 and in TA 1537 in both the presence and absence of S9. No evidence of cytotoxicity was apparent; precipitation occurred at the highest tested dose, though scoring was reportedly unaffected. 

 

Overall, rhodiumtrijodide was found to be mutagenic in S. typhimurium strains TA 1537, TA 98 and TA 100 in the absence and presence of S9, as well as in strain TA 1535 in the absence of S9 alone, under the conditions of the test. However, the authors do not comment on an ambiguous result seen in E. coli WP2uvrA in the absence of metabolic activation, where treatment at the maximum tested dose level induced a near-doubling in the number of revertant colonies.