Methyl (R)-2-(4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy)propionate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

Additional documentation provided in IUCLID assesment reports (Chapter 13) supports the read across approach

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Additional documentation provided in IUCLID assesment reports (Chapter 13) supports the read across approach

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Conclusions:

Negative in rat bone marrow micronucleus erythrocytes assay

Executive summary:

The test substance was evaluated in the rat bone marrow micronucleus test for genotoxic activity. The micronucleus test is capable of detecting agents that cause chromosomal aberrations and spindle malfunction. The test substance was administered to male and female SD rats by single oral gavage at dose levels of 0 (negative control), 30, 100 and 300 mg/kg. The positive control rats received a single dose oral gavage of 20 mg/kg cyclophosphamide, a well-known clastogen. The animals were sacrificed at 30 and 42 h after treatment. 1000 PCE were examined from the bone marrow smears of each animal and the number of micronucleated normochromatic erythrocytes, the  number of micronucleated normochromatic erythrocytes and the number of normochromatic erythrocytes were recorded. The frequency of micronucleated bone marrow erythrocytes was unaffected by test substance treatment. Rats treated with cyclophosphamide, on the other hand, had significant numbers of micronucleated bone marrow erythrocytes. The results of the present study indicate a lack of genotoxic activity for test substance within the test system employed.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1982

Report date:

1982

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test substance was administered to male and female SD rats by single oral gavage at dose levels of 0, 30, 100 and 300 mg/kg. The animals were sacrificed at 30 and 42 h after treatment. 1000 PCE were examined from the bone marrow smears of each animal and the number of micronucleated normochromatic erythrocytes, the number of micronucleated normochromatic erythrocytes and the number of normochromatic erythrocytes were recorded.

GLP compliance:

yes

Type of assay:

mammalian erythrocyte micronucleus test

Test material

Test material information

Constituent 1

Reference substance name:

(2R)-2-[4-[3-chloro-5-(trifluoromethyl)pyridin-2-yl]oxyphenoxy]propanoic acid

Cas Number:

95977-29-0

Molecular formula:

C15H11ClF3NO4

IUPAC Name:

(2R)-2-[4-[3-chloro-5-(trifluoromethyl)pyridin-2-yl]oxyphenoxy]propanoic acid

Test material form:

liquid

Specific details on test material used for the study:

DOWCO 453
Lot #: AGR-187381
Purity: 99.55%

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Timco, Inc., Houston, Texas
- Age at arival: Approximately 8 weeks
- Assigned to test groups randomly: Yes
- Housing: Housed singly in suspended wire-bottom cages
- Diet: Purina Certified Rodent Chow #5002
- Water: Well water
- Acclimation period: 7-8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 72 ± 5
- Humidity (%): 40-60%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12 h dark/light

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: The test substance was solubilized in 100 mL of 1N NaOH. To this, 70 mL of deionized distilled water was added.

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: As test substance was not soluble in water, aqueous solutions of this chemical were prepared in the following way: To prepare a 7.0% stock solution, 17.5 g of test substance was solubilized in 100 mL of 1 N NaOH. To this, 70 ml of deionized distilled (d.d) water was added and the pH was adjusted to about 6.0 by adding (approximately 35 mL) 1.2 N HCl. The contents were brought up to 250 ml by adding d.d water. The stock solution was diluted with d.d. water to the desired concentration. All the solutions used for dosing were less than 60 hours old. The test substance solutions prepared by solubilization in 1 N NaOH were found to be stable for at least 42 days.

Duration of treatment / exposure:

Single oral administration

Frequency of treatment:

Single oral administration

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

30 mg/kg bw (total dose)

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw (total dose)

Doses / concentrations 3

Dose / conc.:

300 mg/kg bw (total dose)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control(s):

- Positive control used: Cyclophosphamide
- Route of administration: Oral gavage
- Doses / concentrations: 20 mg/kg

Examinations

Tissues and cell types examined:

Bone marrow cells from femurs

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION: The dose levels of the test substance used in the study were selected on the basis of LD50 studies conducted in the test facility, which allowed to assume that the single-dose oral LD50 is 500 mg/kg body weight for both sexes. The top dose level of 300 mg/kg used in the study was 60% of the LD50.

TREATMENT AND SAMPLING TIMES: Single oral dose and the treated animals were sacrificed at 30 and 42 h after treatment

DETAILS OF SLIDE PREPARATION: Cell smears were prepared on clean microscope slides using small portions of the cell suspension. The slides were allowed to air dry at least over night. For staining, the slides were fixed for 5 minutes in absolute methanol, rinsed thoroughly in buffer (pH 6.8), stained in Giemsa (1:6 Gurr's R66 Giemsa:buffer, pH 6.8) for 10 minutes, and rinsed thoroughly in buffer (pH 6.8). The slides were blotted with filter paper to remove excess water and allowed to air dry before being cover slipped.

METHOD OF ANALYSIS: The slides were divided into two groups according to sex, coded, and scored blindly. One thousand polychromatic erythrocytes were examined from each animal and the following information was recorded: (1) the number of micronucleated polychromatic erythrocytes (MN-PCE); (2) the number of micronuc1eated normochromatic erythrocytes (MN-NCE) in the optical field containing 1000 PCE; and (3) the number of normochromatic erythrocytes in the optical field containing 1000 PCE. The frequencies of micronucleated cells were expressed as the number of micronucleated erythrocytes in the optical field containing 1000 PCE.

Statistics:

The frequencies of total micronucleated erythrocytes were analyzed by two-way analysis of variance (sex and dose) followed by linear dose-response tests. The frequencies were not transformed prior to analysis. The level of confidence chose was 95% or greater. The data on the proportion of PCE were no evaluated statistically.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

There was a noticeable decrease in the proportions of PCE in females treated with 100 and 300 mg/kg at both sacrifice times. In males, such an effect was observed only in the 300 mg/kg group sacrificed at 42 h. Nevertheless, the decreases in the proportion of PCE noticed in the treatment groups were not sufficient to interfere with detection of any induced micronucleated erythrocytes. It is possible that at least part of the decreases in the proportion of PCE may be due to the nonspecific toxicological stress (in the present situation, decreased food consumption) encountered by the animals.

Any other information on results incl. tables

Table-1: Summary of the data on the incidence of micronucleated erythrocytes and the % of PCE in the bone marrows of male and female rats in the various treatment groups

			30 h sacrifice		42 h sacrifice
Treatment	Sex	No. of animals^A	Total MN^B± SD	% PCE^C± SD	Total MN^B± SD	% PCE^C± SD
Negative control	M	5	3.2 ± 1.9	72.9 ± 2.7	4.0 ± 2.3	79.6 ± 7.3
	F	5	3.2 ± 0.4	71.5 ± 5.6	2.6 ± 2.1	67.6 ± 3.2
30 mg/kg	M	5	2.4 ± 1.5	76.2 ± 3.5	4.2 ± 3.3	74.2 ± 4.4
	F	5	4.2 ± 1.9	68.8 ± 5.2	3.8 ± 3.6	62.1 ± 5.5
100 mg/kg	M	5	2.4 ± 1.5	69.8 ± 3.4	5.0 ± 1.2	73.4 ± 4.5
	F	5	2.8 ± 1.5	60.7 ± 5.0	3.2 ± 2.9	51.9 ± 15.5
300 mg/kg	M	5	3.0 ± 2.3	67.2 ± 4.3	2.6 ± 2.1	65.1 ± 6.0
	F	5	2.6 ± 0.5	55.8 ± 6.6	1.6 ± 1.3	54.9 ± 6.3
20 mg/kg (cyclophosphamide)	M	5			37.2^D± 7.2	46.2 ± 6.4
	F	5			37.8^D± 8.1	30.1 ± 3.2

A 1000 PCE were examined from each animal

B Total number of micronucleated erythrocytes per 1000 PCE per animal

C PCE x 100 / PCE + NCE

D Analysis of variance showed significant difference between negative control and CP treatment, p <0.0001

Applicant's summary and conclusion

Conclusions:

Negative in rat bone marrow micronucleus erythrocytes assay

Executive summary:

The test substance was evaluated in the rat bone marrow micronucleus test for genotoxic activity. The micronucleus test is capable of detecting agents that cause chromosomal aberrations and spindle malfunction. The test substance was administered to male and female SD rats by single oral gavage at dose levels of 0 (negative control), 30, 100 and 300 mg/kg. The positive control rats received a single dose oral gavage of 20 mg/kg cyclophosphamide, a well-known clastogen. The animals were sacrificed at 30 and 42 h after treatment. 1000 PCE were examined from the bone marrow smears of each animal and the number of micronucleated normochromatic erythrocytes, the  number of micronucleated normochromatic erythrocytes and the number of normochromatic erythrocytes were recorded. The frequency of micronucleated bone marrow erythrocytes was unaffected by test substance treatment. Rats treated with cyclophosphamide, on the other hand, had significant numbers of micronucleated bone marrow erythrocytes. The results of the present study indicate a lack of genotoxic activity for test substance within the test system employed.