3-(5-chlorobenzoxazol-2-yl)-7-(diethylamino)-2-benzopyrone

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1990/1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

3-(5-chlorobenzoxazol-2-yl)-7-(diethylamino)-2-benzopyrone

EC Number:

252-722-2

EC Name:

3-(5-chlorobenzoxazol-2-yl)-7-(diethylamino)-2-benzopyrone

Cas Number:

35773-43-4

Molecular formula:

C20H17ClN2O3

IUPAC Name:

3-(5-chloro-1,3-benzoxazol-2-yl)-7-(diethylamino)-2H-chromen-2-one

Test material form:

solid: particulate/powder

Test animals

Species:

mouse

Strain:

NMRI

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: F. Winkelmann, Borchen
- Age at study initiation: 8 to 12 weeks
- Weight at study initiation: 28-43 g
- Assigned to test groups randomly: yes
- Fasting period before study:
- Housing: females: up to 3/cage; males: single
- Diet (ad libitum): Altromin 1324 standard diet
- Water (ad libitum): tap water
- Acclimation period: at least one week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22+/-0.5
- Humidity (%): 43-50
- Air changes (per hr): ca. 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 16 Oct 1990 To:30 Nov 1990

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

0.5 % aqueous Cremophor emulsion

Details on exposure:

suspension in 0.5 % aqueous Cremophor emulsion; 5 minutes sonification; stirring with magetic mixer until administration

Duration of treatment / exposure:

treatment: 16, 24 and 48 hrs after treatment
controls: 24 hours

Frequency of treatment:

once

Doses / concentrations

Dose / conc.:

10 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control(s):

- Positive control: Cyclophosphamide
- Route of administration: i.p.
- Doses / concentrations: 20 mg/kg bw

Examinations

Tissues and cell types examined:

bone marrow (from femur)

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION:
The selection of the test item was based on a pilot test, in which groups of five animals, including both males and females, were intraperitoneally administered 1000, 2500 and 10000 mg/kg body weight. No animals died.The following symptoms were recorded, starting at 1000 mg/kg: apathy, roughened fur, staggering gait, spasm, eyelids stuck together, yellowish disoloured skin of hairless parts and urine. Based on these results, 10000 mg/kg was chosen for the main test.

Evaluation criteria:

Assessment criteria:
A test was considered positive if, at any of the intervals, there was relevant and significant increase in the number of polychromatic erythrocytes showing micronucleated in comparison to the negative control.
A test was considered negative if there was no relevant or significant increase in the rate of micronucleated polychromatic erythrocytes at any time. A test was also considered negative if there was a significant increase in that rate which, according to the laboratory's experience) was within the range of negative controls.
In addition, a test was considered equivocal if there was an increase of micronucleated polychromatic erythrocytes above the range of attached historical negative controls, provided the increase was not significant. In this case, a second test had to be performed at the most sensitive interval.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Positive controls validity:

valid

Applicant's summary and conclusion

Conclusions:

In a GLP study according to OECD test guideline 474, no indication of a clastogenic effect at 10000 mg/kg bw test substance in the micronucleus test in the mouse was observed. The substance is not considered to be a clastogen in mammalia.

Executive summary:

The micronucleus test was used in order to investigate the test item in male and female mice for a possible clastogenic effect on the chromosomes of bone-marrow erythroblasts. The known clastogen and cytostatic agent; i.e. cyclophosphamide, served as positive control.

The treated animals received a single intraperitoneal administration of either the test item or cyclophosphamide. The femoral marrow of groups treated with the test item was prepared 16, 24 and 48 hours after administration. All negative and positive control animals were sacrificed after 24 hours. The dose of the test item and the positive control, cyclophosphamide, were 10000 and 20 mg/kg body weight, respectively.

The animals treated with the test item, showed some symptoms of toxicity after administration. However all animals survived until the end of the test.

No indications of a clastogenic effect of the test item were found after a single intraperitionael treatment with 10000 mg/kg bw. Furthermore, the known mutagen and clastogen cyclophosphamide, the positive control, had a clear clastogenic effect at an intraperitoneal dose of 20 mg/kg bw as is shown by the biologically relevant increase in polychromatic erythrocytes with micronuclei. The ratio of polychromatic to monochromatic erythrocytes was not altered.