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Key value for chemical safety assessment

Genetic toxicity in vitro

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Link to relevant study records
Reference
Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: other: genetic toxicity in vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
yes
Type of assay:
other: genetic toxicity in vivo
Species:
mouse
Strain:
NMRI
Route of administration:
intraperitoneal
Vehicle:
water
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes

This study was performed to investigate the potential of the substance to induce micronuclei in

polychromatic erythrocytes (PCE) in the bone marrow of the mouse. The test item was

formulated in deionised water, which was also used as vehicle control. The compound was

administered by a single intraperitoneal injection, and bone marrow cells were collected 24

h and 48 h later. Ten animals (5 males, 5 females) per test group were included and at

least 2000 polychromatic erythrocytes (PCEs) per animal were scored for micronuclei. The

ratio between polychromatic and total erythrocytes was determined in the same sample and

reported as the number of PCEs per 2000 erythrocytes. The following dose levels of the test

item were investigated: 24-h preparation interval: 12.5, 25 and 50 mg/kg bw; 48-h

preparation interval: 50 mg/kg bw. As estimated by pre-experiments, 50 mg substance per kg

bw was the highest applicable dose without significant effects on the survival rates, but with

clear signs of toxicity. At a higher dose (75 mg/kg) all treated animals had to be killed after

10 minutes due to the severity of the induced toxic effects.

Results

The number of PCEs was not substantially decreased in the treated animals as compared

with the vehicle control group, indicating that the substance did not exert any cytotoxic effects on

the bone marrow. The test item was, however, bioavailable as suggested by chemical

analysis of the blood of the treated animals. In comparison with the corresponding vehicle

controls, there was reported to be no biologically relevant or statistically significant

enhancement in the frequency of the detected micronuclei at any preparation interval after

administration of the test item and with any dose level used.

It should be noted that in the 24-h sampling time all doses of the substance resulted in about

doubling of the micronucleus frequency of the vehicle controls. The difference to control was

2.4-, 2.1-, and 2.0-fold, at 12.5, 25, and 50 mg/kg, respectively and was of borderline

significance at 12.5 mg/kg (P=0.0658) and at 25 mg/kg (P=0.0816) in the Mann-Whitney

test. No dose-response was, however, evident, and the micronucleus frequencies were in

general low and within historical control range.

Conclusion

Under the experimental conditions reported, the test item did not significantly induce

micronuclei in mouse bone marrow polychromatic erythrocytes. Therefore, the substance was

considered to be negative in the micronucleus assay. Negative and positive controls were in

accordance with the OECD guideline. Dose selection was based on a dose range-finding

assay.

Comment

At the 24-h sampling time, there was a doubling of mean micronucleus frequencies at all

doses used. The differences were not statistically significant, although borderline, the

numbers of micronucleated cells were, in general, low, and there was no dose-response.

Consequently, it is not biologically relevant.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vivo:

In summary, although the test substance induced chromosome aberrations in vitro in the absence and presence of metabolic activation (OECD 473), the in vivo bone marrow micronucleus test in mice (OECD 474) was negative as were the Ames test (OECD 471, with and without metabolic activation) and the in vitro mammalian cell gene mutation test (OECD 476, with and without metabolic activation), suggesting that the clastogenic potential of the test substance is not seen under in vivo conditions.

Justification for classification or non-classification

At the found effect levels there is no requirement for classification