Isooctyl acetate

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 December 1993 - 28 March 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1994

Report date:

1994

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 84-2

Deviations:

yes

Remarks:

analysis of the test substance mixtures was not performed

GLP compliance:

yes (incl. QA statement)

Remarks:

Analysis for stability, uniformity and concentration verification was not performed.

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Isooctyl acetate

EC Number:

250-701-2

EC Name:

Isooctyl acetate

Cas Number:

31565-19-2

Molecular formula:

C10H20O2

IUPAC Name:

Acetic acid, isooctyl ester

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Exxon Chemical Company Lot Number: 111991
- Expiration date of the lot/batch: 31 October 1998

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room Temperature
- Solubility and stability of the test substance in the solvent/vehicle: Soluble in DMSO

Method

Species / strain

Species / strain / cell type:

other: S. typhimurium TA 1535, TA 1537, TA 1538, TA 98, and TA 100

Details on mammalian cell type (if applicable):

CELLS USED
- Source of cells: Dr. B. N. Ames, Department of Biochemistry, University of California, Berkeley, California.

Metabolic activation:

with and without

Metabolic activation system:

Liver homogenate from the livers of Aroclor 1254 pretreated Sprague Dawley rats (S9)

Test concentrations with justification for top dose:

50, 100, 200, 400, 600 ug/plate initial assay
In a pretoxicity test, toxicity as either a reduction in the number of revertant colonies or a reduction in the background lawn, was observed beginning at test concentration 500 ug/plate with and without metabolic activation. Based on these results 600 ug/plate was selected as the high dose.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: The vehicle was considered, under the conditions of the assay, to be stable for the duration of the assay in that it performed in a manner consistent with data from previous studies.

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

yes

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

other: 2-Aminoanthracene and N-Methyl-N-Nitro-N-Nitrosoguanidine

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: 2 days

NUMBER OF REPLICATIONS: three

Evaluation criteria:

An individual dose is considered positive if the mean colony count on the test plates is equal to or greater than three times the mean number of spontaneous revertants on the vehicle control plates. A positive result for the assay is defined as a reproducible dose-related increase in the number of revertant colonies over at least 3 concentrations of test material including at least one positive dose.

Statistics:

The mean plate count and standard deviation for each dose point were determined.

Results and discussion

Test results

Key result

Species / strain:

other: S. typhimurium TA 1535, TA 1537, TA 1538, TA 98 and TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

To determine the highest dose of test substance to be used in the assay a dose range from 1 to 10,000 ug/plate was tested in TA98. An increase in revertant colonies was not observed at any of the concentrations tested. Toxicity, seen as either a reduction in the number of revertant colonies or a reduction in the background lawn, was observed beginning at test concentration 500 ug/plate with and without metabolic activation. Based on these results, test concentrations of 50 to 600 ug/plate were tested in the initial assay. Due to toxicity in the initial assay a repeat assay was performed using test concentrations of 25 to 400 ug/plate.

In the initial mutagenesis assay, neither a positive response nor a dose related increase was observed for any of the tester strains. Toxicity, either a reduction in the number of revertant colonies or a reduction in the background lawn, was observed for all tester strains with and without metabolic activation. In the repeat mutagenesis assay, neither a positive response nor a dose related increase was observed for any of the tester strains. Toxicity, either a reduction in the number of revertant colonies or a reduction in the background lawn, was observed for all tester strains with and without metabolic activation, except for TA1535 with (+ S9) metabolic activation.

Applicant's summary and conclusion

Conclusions:

Neither a positive dose nor a dose related increase was observed for any of the tester strains with or without metabolic activation in either the initial or repeat assays. Under the conditions of the assay, MRD-93-688 was not mutagenic for the Salmonella test strains at doses up to and including 600 ug/plate.

Executive summary:

The microbial mutagenesis assay (Ames Assay), developed by B. N. Ames and coworkers (1975) is a test for the ability of a compound to cause reverse mutation at the histidine locus in bacteria (from nutritional histidine dependence to histidine independence). Five special tester strains of Salmonella typhimurium, which were sensitive to frameshift or base pair mutagens, were employed. Positive test results are considered to provide presumptive evidence of mutagenic potential in mammalian species.

This assay was conducted to determine if Exxate 800 (MRD-93-688) was capable of causing reverse mutations in these special tester strains of bacteria with and without metabolic activation.

The test substance was diluted in DMSO, A toxicity pretest was performed to determine the highest concentration of test substance to be used in the initial assay. Test concentrations of 1 to 10,000 fig/plate were tested with and without metabolic activation in tester strain TA98.

The test substance did not induce an increase in revertant colonies at any of the concentrations tested. Toxicity, seen as either a reduction in the number of revertant colonies or a reduction in the background lawn, was observed beginning at test concentration 500 ug/plate with and without metabolic activation.

Based on these results, test concentrations of 50 to 600 ug/plate were tested in the initial assay. A repeat assay was performed using test concentrations of 25 to 400 ug/plate.

Neither a positive dose nor a dose related increase was observed for any of the tester strains with or without metabolic activation. Therefore, Exxate 800 (MRD-93-688) was not considered to be mutagenic under the various conditions of testing.

Toxicity, as seen by either a reduction in the number of reverent colonies or reduction in the background lawn; was observed for all five tester strains with and without metabolic activation in both the initial and repeat assays, except for tester strain TA1535 with metabolic activation in the repeat assay.

Both the negative and positive controls responded in an appropriate manner.