Ethyl 2,3-epoxy-3-phenylbutyrate

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Meets generally accepted scientific standards, well documented and acceptable for assessment.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Galloway SM, Bloom AD, Resnick M, Margolin BH, Nakamura F, Archer P, Zeiger E (1985): Development of a standard protocol for in vitro cytogenetic testing with Chinese hamster ovary cells. Environ Mutagen 7: 1-51.

GLP compliance:

not specified

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

Ethyl 2,3-epoxy-3-phenylbutyrate

EC Number:

201-061-8

EC Name:

Ethyl 2,3-epoxy-3-phenylbutyrate

Cas Number:

77-83-8

Molecular formula:

C₁₂H₁₄O₃

IUPAC Name:

ethyl 3-methyl-3-phenyloxirane-2-carboxylate

Details on test material:

- Names of test material (as cited in study report): 3-methyl-3-phenylglycidic acid, ethyl ester, CAS No. 77-83-8
- Substance type: No data
- Physical state: No data
- Analytical purity: No data
- Impurities (identity and concentrations): No data
- Composition of test material, percentage of components: No data
- Isomers composition: No data
- Purity test date: No data
- Lot/batch No: No data
- Expiration date of the lot/batch: No data
- Stability under test conditions: No data
- Storage condition of test material: No data
- Other: Source: National Toxicology Program chemical repository (Radian Corp., Austin, TX)

Method

Species / strain

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Details on mammalian cell type (if applicable):

- Cell line: CHO-W-B1
- Type and identity of media: McCoy's 5a medium with 5 % foetal calf serum, L-glutamine and antibiotics.

Metabolic activation:

with and without

Metabolic activation system:

S9 mix consisting of 15 µL/mL liver homogenate (from male Sprague-Dawley rats, induced with Aroclor 1254), 2.4 mg/mL NADP, and 4.5 mg/mL isocitric acid in serum-free medium.

Test concentrations with justification for top dose:

50 µg/mL, 160 µg/mL, 500 µg/mL (half-log increments).

Vehicle / solvent:

- Solvents used: either water, dimethyl sulfoxide (DMSO), ethanol or acetone, in that order of preference. It is unclear which solvent was used for the test material.

Controls

Controls 1

Negative solvent / vehicle controls:

yes

Remarks:

Solvents used: either water, dimethyl sulfoxide (DMSO), ethanol or acetone, in that order of preference. It is unclear which solvent was used for the test material.

Controls 2

Positive controls:

yes

Positive control substance:

mitomycin C

Remarks:

Migrated to IUCLID6: Concentration - 0.15 µg/mL. Without metabolic activation only.

Controls 3

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

Migrated to IUCLID6: Concentration - 15 µg/mL. With metabolic activation only.

Details on test system and experimental conditions:

METHOD OF APPLICATION: In medium.

DOSE SELECTION
- Doses were chosen for the aberration test based on a preliminary test of cell survival 24 hrs after treatment. For most tests, doses were based on observations of cell confluence and mitotic cell availability in the SCE test (reported elsewhere).

DURATION
- Exposure duration:
-- With S9 mix: 2 hr
-- Without S mix: Throughout incubation period
- Expression time (cells in growth medium):
- Fixation time (start of exposure up to fixation or harvest of cells): 8 to 12 hr standard (cells in first mitosis). In cases where experience suggested that mitosis was delayed by the presence of the test material, harvesting was delayed to "e.g. 18-26 hr".

STAIN (for cytogenetic assays): Giemsa

NUMBER OF REPLICATIONS: 1

EVALUATIONS
- No. of cells evaluated: 100 cells from each of the 3 highest groups having sufficient metaphases for analysis, and from positive and solvent controls.
- Determination of polyploidy: Aberrations from polyploid cells not scored, but metaphases with 19-23 chromosomes were used.
- All types of aberrations were recorded separately, but for data analysis they were grouped into categories of "simple" (breaks and terminal deletions), "complex" (exchanges and rearrangements), "other" (including pulverised chromosomes), and "total".

Statistics:

Linear regression analysis of the percentage of cells with aberrations vs the log-dose was used as the test for trend. To examine absolute increases over control levels at each dose, a binomial sampling assumption (as opposed to Poisson) was used, Margolin et al. (1983). The P values were adjusted by Dunnett's method to take into account the multiple dose comparisons. For data analysis, the "total" aberration category was used and the criterion for a positive response was that the adjusted P value be ≤ 0.05

Results and discussion

Test results

Test results 1

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 2

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with

Genotoxicity:

ambiguous

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Metabolic activation	Result	Range (µg/mL)	Least effect concentration (µg/mL)
Without S9 mix	+	50 - 500	< 50
With S9 mix	?	50 - 500	500

The least effective concentration tested (LEC) is the lowest dose to give a statistically significant increase (P ≤ 0.05) in aberrations. For chemicals with which the lowest dose tested gave a positive response, the LEC is preceded by "<".

Results without metabolic activation

Harvest time: 14 hrs

Result: Positive

Dose (µg/mL)	Cells	Percentage cells with aberrations
		Total	Simple	Complex
Negative control
0	100	1	0	1
Test material
50	100	8	4	4
160	100	4	4	1
500	100	8	7	1
Positive control - MMC
15	50	34	26	14

Results with metabolic activation

Harvest time: 14 hrs.

Result: Unclear

Dose (µg/mL)	Cells	Percentage cells with aberrations
		Total	Simple	Complex
Negative control
0	100	4	3	1
Test material
50	100	9	7	2
160	100	9	7	2
500	100	12	10	2
Positive control - CP
0.15	50	28	18	14

Applicant's summary and conclusion

Conclusions:

Interpretation of results:
positive without metabolic activation
ambiguous with metabolic activation

Galloway et al. found that the test material was positive without metabolic activation, and ambiguous with metabolic activation in a chromosome aberration test for genotoxicity.