methyl (2E)-{2-[(2,5-dimethylphenoxy)methyl]phenyl}(methoxyimino)ethanoate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study performed under GLP regulations

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5395 (In Vivo Mammalian Cytogenetics Tests: Erythrocyte Micronucleus Assay)

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Reference

Name:

Unnamed

Type:

Constituent

Details on test material:

- Name of test material (as cited in study report): MEOE
- Analytical purity: 96% ± 1 (see analytical report 061L00055)
- Test substance No.: 04/0450-2

Test animals

Species:

mouse

Strain:

NMRI

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Germany GmbH
- Age at study initiation: 5-8 weeks
- Weight at study initiation: about 30 g (mean)
- Housing: Single in Makrolon cages, type MI
- Diet (e.g. ad libitum): Standard ized pelleted feed, Provimi Kliba SA, Kaiseraugst, Switzerland
- Water (ad libitum): Drinking water
- Acclimation period: At least 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle: corn oil
- Justification for choice of solvent/vehicle: Due to the good suspensibility of the test substance in corn oil, corn oil was selected as the vehicle, which had been demonstrated to be suitable in the in vivo micronucleus test and for which historical data are available.

Duration of treatment / exposure:

24 hours for 500 and 1000 mg/kg bw doses
24 and 48 hours for the 2000 mg/kg bw dose

Frequency of treatment:

once

Doses / concentrations

Remarks:

Doses / Concentrations:
500, 1000 and 2000 mg/kg bw
Basis:
nominal conc.

No. of animals per sex per dose:

5

Control animals:

yes

Positive control(s):

Cyclohexylamine (CPP) 20 mg/kg bw for clastogenic effects
Vincristine Sulphate (VCR) 0.15 mg/kg bw dor aneugenic effects
both dissolved in purified water.
- Justification for choice of positive control(s): The stability of CPP and VCR is welI-defined under the selected conditions, since both
positive control articles are well-established reference clastogens and aneugens respectively.
- Route of administration: orally in a volume of 10 mL/kg bw.

Examinations

Tissues and cell types examined:

Polychromatic erythrocytes (PCE) in the bone marrow.

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION:
In a pretest for the determination of the acute oral toxicity, at 2 000 mg/kg bw recommended as the highest dose according to the OECD Guideline all animals (male and female) survived. The clinical signs only observed were squatting posture and soft feces. However, there were no distinct differences in the symptoms between males and females. Thus, only male animals were used for the cytogenetic investigations.

TREATMENT AND SAMPLING TIMES:
The animais were treated once and samples of bone marrow were taken 24 hours and 48 hours after the treatment.

DETAILS OF SLIDE PREPARATION:
The animals were sacrificed by cervical dislocation. The femora were removed, the epiphyses were cut off and the marrow was flushed out with fetal calf serum. The cell suspension was centrifuged at 300 x g for 5 minutes and the supernatant was discarded. A drop of the resuspended cell pellet was spread on a slide. The smear was air-dried and then stained with May-Grünwald/Giemsa. Cover slips were mounted in Corbit-Balsam.

METHOD OF ANALYSIS:
In general, 2000 polychromatic erythrocytes (PCE) were analysed per animal for micronuclei (MN). To describe a cytotoxic effect the ratio between polychromatic and normochromatic erythrocytes was determined in the same sample and expressed in normochromatic erythrocytes per 2000 PCEs . The analysis was performed with coded slides.

Evaluation criteria:

A Test substance is considered positive if the following criteria are met:
- Significant and dose-related increase in the number of PCEs containing micronuclei.
- The number of PCEs containing micronuclei has to exceed both the concurrent negative control and the highest value of the historical control range.

A test substance is considered negative if the following criteria are met:
- The number of cells containing micronuclei in the dose groups is not significantly above the negative control and is within the historical control data

Statistics:

The statistical evaluation of the data was carried out using the program system MUKERN (BASF AG).

Results and discussion

Test results

Sex:

male

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Any other information on results incl. tables

The single oral administration of corn oil in a volume of 20 mL/kg body weight led to 0.9‰ polychromatic erythrocytes containing micronuclei after the 24-hour sacrifice interval or to 1.5‰ after the 48-hour sacrifice interval.

After the single administration of the highest dose of 2000 mg/kg body weight, 1.0‰ polychromatic erythrocytes containing micronuclei were found after each 24 hours and 48 hours.

In the two lower dose groups, rates of micronuclei of about 1.5‰ (1000 mg/kg group) and 1.7‰ (500 mg/kg group) were detected after a sacrifice interval of 24 hours in each case.

With 27.2‰ the positive control substance cyclophosphamide for clastogenicity, as expected, led to a clear increase in the number of polychromatic erythrocytes containing exclusively small micronuclei.

Vincristine, a spindle poison agent, produced a 43.6‰ increase in micronuclei in polychromatic erythrocytes. A significant portion increase, 11.1‰ was attributable to large micronuclei.

The number of normochromatic erythrocytes containing micronuclei did not differ to any appreciable extent in the negative control or in the various dose groups at any of the sacrifice intervals.

No inhibition of erythropoiesis induced by the treatment of mice with MEOE was detected at any doses; the ratio of polychromatic to normochromatic erythrocytes was always in the same range as that of the control values in all dose groups.