(hydroxyethyl)urea

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline-conform study performed under GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

EXP 3982 (N-2-hydroxyethylurea)

IUPAC Name:

EXP 3982 (N-2-hydroxyethylurea)

Details on test material:

- Name of test material (as cited in study report): EXP 3982 (N-2-hydroxyethylurea)
- Physical state: clear slightly yellow liquid
- Analytical purity: aqueous solution containing 57.58% hydroxyethyl urea
- Impurities (identity and concentrations): not reported
- Composition: aequeous solution containing 57.58 % hydroxyethyl urea
- Purity test date: not reported
- Lot/batch No.: not reported
- Expiration date of the lot/batch: 15 July 2001
- Storage condition of test material: at ambient temperature protected from freezing

Method

Target gene:

Histidine locus for Salmonella
Tryptophan locus for E. Coli

Species / strain

Species / strain / cell type:

other: S. typhimurium TA 1535, TA 1537, TA 98 and TA 100; E. coli: WP2 uvrA

Metabolic activation:

with and without

Metabolic activation system:

Aroclor-induced rat liver S9 mix

Test concentrations with justification for top dose:

The dosing solutions were adjusted to compensate for the purity (57.58%) of the test article. Doses were as follows:

Initial Toxicity-Mutation Assay, without S9: 2.5, 7.5, 25, 75, 200, 600, 1800, 5000 µg/plate
Initial Toxicity-Mutation Assay, with S9: 2.5, 7.5, 25, 75, 200, 600, 1800, 5000 µg/plate
Confirmatory Mutatgenicity Assay, without S9: 75, 200, 600, 1800, 5000 µg/plate
Confirmatory Mutatgenicity Assay, with S9: 75, 200, 600, 1800, 5000 µg/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: water
- Justification for choice of solvent/vehicle: selected based on compatibility with the target cells and solubility of the test article (soluble in water at a maximum concentration of approximately 50 mg/mL, the highest concentration tested)

Controls

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: With S9: 2-amonoanthracene. Without S9: 2-nitrofluorene (TA98), Sodium azide (TA100, TA1535), 9-aminoacridine (TA1537), Methyl methanesulfonate (WP2 uvrA)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: 48 - 72 h

NUMBER OF REPLICATIONS:
Initial Toxicity-Mutation Assay: 2
Confirmatory Mutatgenicity Assay: 3

DETERMINATION OF CYTOTOXICITY
- Method: The condition of the bacterial background lawn was evaluated for evidence of test article toxicity by using a dissecting microscope.

Evaluation criteria:

For the test article to be evaluated positive, it must cause a dose-related increase in the mean revertants per plate of at least one tester strain over a minimum of two increasing concentrations of test article. Data sets for tester strains TA1535 and TA1537 were judged positive if the increase in mean revertants at the peak of the dose response is equal to or greater than three times the mean vehicle control value. Data sets for tester strains TA98, TA100 and WP2 uvrA were judged positive if the increase in mean revertants at the peak of the dose response is equal to or greater than two times the mean vehicle control value.

Statistics:

For each replicate plating, the mean and standard deviation of the number of revertants per plate were calculated and are reported.

Results and discussion

Test results

Species / strain:

other: S. typhimurium TA 1535, TA 1537, TA 98 and TA 100; E. coli: WP2 uvrA

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Water solubility: soluble in water at a maximum concentration of approximately 50 mg/mL, the highest concentration tested
- Precipitation: no

RANGE-FINDING/SCREENING STUDIES: In the initial toxicity mutation assay, the maximum dose tested was 5000 µg per plate; this dose was achieved using a concentration of 50 mg/mL and a 100 µL plating aliquot. Neither precipitate nor appreciable toxicity was observed. Based on the findings of the toxicity assay, the maximal dose plated in the mutagenicity assay was 5000 µg per plate.

COMPARISON WITH HISTORICAL CONTROL DATA: The mean revertants per plate in the negative and positive controls were in the range of the historical control data.

ADDITIONAL INFORMATION ON CYTOTOXICITY: No appreciable toxicity was observed in either assay.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

The results of the Bacterial Reverse Mutation Assay indicate that, under the conditions of this study, EXP 3982 (N-2-hydroxyethylurea) did not cause a positive response in the presence and absence of Aroclor-induced rat liver S9 mix.

Executive summary:

The test article, EXP 3982 (N-2-hydroxyethylurea), was tested under GLP in the Bacterial Reverse Mutation Assay using Salmonella typhimurium tester strains TA98, TA100, TA1535 and TA1537 and Escherichia coli tester strain WP2 uvrA in the presence and absence of Aroclor-induced rat liver S9 mix. The study followed the method outlined in OECD TG 471.

The assay was performed in two phases, using the plate incorporation method. The first phase, the preliminary toxicity-mutation assay, was used to establish the dose-range for the mutagenicity assay and to provide a preliminary mutagenicity evaluation. The second phase, the mutagenicity assay, was used to evaluate and confirm the mutagenic potential of the test article. The dosing solutions were adjusted to compensate for the the concentration of hydroxyethyl urea (57.58%) in the test substance.

Water was selected as the solvent of choice based on compatibility with the target cells and solubility of the test article. The test article was soluble in water at a maximum concentration of approximately 50 mg/mL, the highest concentration tested.

In the initial toxicity-mutation assay, the maximum dose tested was 5000 µg per plate; this dose was achieved using a concentration of 50 mg/mL and a 100 µL plating aliquot. Neither precipitate nor appreciable toxicity was observed. Based on the findings of the toxicity-mutation assay, the maximum dose plated in the mutagenicity assay was 5000 µg per plate. In the confirmatory mutagenicity assay, no positive response was observed. Neither precipitate nor appreciable toxicity was observed.

Under the conditions of this study, test article EXP 3982 (N-2-hydroxyethylurea) was concluded to be negative in the Bacterial Reverse Mutation Assay.