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Toxicological information

Genetic toxicity: in vivo

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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: According to OECD Guideline and GLP

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1999
Report Date:
1999
Reference Type:
other: abstract
Title:
Unnamed
Year:
1999

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
yes
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
Ro 1525 corresponds to Colipa A 155
Ro 1525
SAT 9803 75
Batch-No.: Ro-Rn 6567-083

Test animals

Species:
mouse
Strain:
NMRI
Sex:
male/female

Administration / exposure

Route of administration:
oral: gavage
Duration of treatment / exposure:
one application
Frequency of treatment:
once at doses
Post exposure period:
24 h/48 h
Doses / concentrations
Remarks:
Doses / Concentrations:
50, 100, 150 mg/kg bw
Basis:
actual ingested
No. of animals per sex per dose:
5
Control animals:
yes
Positive control(s):
One positive control group (40 mg/kg bw) cyclophosphamide

Examinations

Tissues and cell types examined:
Bone marrow cells

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
no effects
Remarks:
no pronounced cytotoxicity to the bone marrow, slightly lower ratios of polychromatic/normochromatic erythroctes in females of all dose groups
Vehicle controls valid:
yes
Negative controls valid:
not applicable
Positive controls valid:
yes

Any other information on results incl. tables

There were no statistically significant differences in mean body weights between the groups, neither at allocation nor at administration.

Mortality

5/15 females and 3/15 males of the high dose groups and of the high dosed spare group died within 48 hours p.a. All deceased aimals of the high dose group were replaced by spare animals. In the mid dose group, 1/5 females died within 24 hours p.a.

No mortality occurred in the low dose group.

No marked or significant differences in the mean amounts of nucleated cells or of polychromatic erythrocytes or of the ratio polychromatic/nonnochromatic erythrocytes were noted at any dose of the test substance in either sex. A slight reduction in the mean amount of polychromatic erythrocytes in females of the high dose group C2, 48 hours p.a., and slightly lower ratios of polychromatic/normochromatic erythrocytes possibly indicate some mild cytotoxicity.

Micronucleated erythrocytes

Rate of micronucleated normochromatic erythrocytes

There was no significant difference in the rate of micronucleated nonnochromatic erythrocytes between the test substance groups and the respective negative control groups at any sampling time, neither in males nor in females.

Rate of micronucleated polychromatic erythrocytes

This is the parameter of major interest. In this test system, a test substance is considered to induce chromosomal damage or damage to the mitotic apparatus, if a significantly increased arnount of micronucleated polychromatic erythrocytes is detected.

The amounts of micronucleated polychromatic erythrocytes were not markedly or statistically significantly higher in the dosed groups than in the corresponding negative control groups, neither 24 nor 48 hours p.a. and neither for males nor for females. There were no doseresponse correlations. A significantly lower amount of micronucleated polychromatic erythrocytes in the high dose

group C2, killed 48 h p.a., is of merely statistical significance, but has no biological relevance. At each dose, the amount of micronucleated polychromatic erythrocytes was also within the range of historical negative control data.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
No pronounced cytotoxicity of "Ro 1525" to the bone marrow was noted at doses of 50, 100 or 150 mg/kg body weight 24 or 48 hours p.a.
Nevertheless, slightly lower ratios of polychromatic/normochromatic erythrocytes in females of all dosed groups may indicate the bioavailability of
the test substance. This is also shown by 20 to 27 % mortality at the doses of 100 and 150 mg/kg.
The rate of micronucleated normochromatic erythrocytes was at both sampling times comparable to that of the respective negative control groups.
The test substance did not cause any marked or statistically significant increase in the rate of rnicronucleated polychromatic erythrocytes, which was the target of this study, neither 24 nor 48 hours p.a., neither in males nor in females. All data were within the range of historical negative control data.
Due to the results obtained in this study "Ro 1525" does not produce micronuclei in polychromatic erythrocytes in both sexes of the test species at
doses of 50, 100 or 150 mg/kg body weight and sampling times of 24 and 48 hours p.a. under test conditions.
Executive summary:

Objective

This study was perfonned to detect the possible production of micronuclei, induced by the test substance, as a result of chromosomal damage or of a damage to the mitotic apparatus in an in vivo test system.

Method

"Ro 1525" was dissolved in deionised water and was administered once at doses of 50, 100 or 150 mg/kg body weight orally by gavage to three groups of 5 male and 5 female Crl:NMRI BR-mice each. These animals were killed 24 hours p.a. Another high dose group of 5 males and 5 fema]es (150 mg/kg body weight) was killed 48 hours p.a. Additionally, one high dose group of 5 male and 5 female spare animals was included to replace possible unscheduled deaths in the high dose group.

Preparation of bone marrow cells and investigations were perfonned in confonnance with the EC Guideline 92/69, Part B.12.

Two negative control groups (deionised water, sampling times 24 and 48 h p.a.) and one positive control group (40 mg cyclophosphamide per kg body weight, dissolved in deionised water, sampling time 24 h p.a.) were included in the study.

The dose volume was 10 m] per kg body weight for all groups.

Results

Positive controls

Cyclophosphamide caused cytotoxicity and produced micronuclei in polychromatic erythrocytes, thus demonstrating the sensitivity of the test system used for the endpoints investigated in this study.

Mortality

5/15 females and 3/15 males of the high dose groups and of the high dosed spare group died within 48 hours p.a. All deceased animals of the high dose group were replaced by spare animals. In the mid dose group, 1/5 females died within 24 hours p.a.

No mortality occurred in the low dose group.

Composition of bone marrow

No significant differences were noted in the amounts of nucleated cel1s or of polychromatic erythrocytes or in the ratios polychromatic to normochromatic erythrocytes. Slightly lower ratios of polychromatic/normochromatic erythrocytes in females of an dosed groups possibly indicate mild cytotoxicity. No pronounced cytotoxicity was noted in any sex at any dose.

Micronucleated erythrocytes

There were no significant differences in micronucleated normochromatic erythrocytes between the test substance group animals of both sexes and the corresponding negative controls, neither 24 nor 48 hours after administration.

However, the parameter of major interest is the amount of micronucleated polychromatic erythrocytes. In this test system, a test substance is considered to induce chromosomal damage or damage to the mitotic apparatus, if a significantly increased amount of micronucleated polychromatic erythrocytes compared to the corresponding negative controls is detected.

The amounts of micronucleated polychromatic erythrocytes were not markedly or statistically significantly higher in the dosed groups than in the corresponding negative control groups, neither 24 nor 48 hours p.a. and neither for males nor for females. All data were within the range of historical negative control data and no dose-response correlationship was established.

Sex differences

Differences in the amounts of nucleated cells between the low dose group males and females and between males and females of one negative control group were of merely statistical significance, but without any biological relevance. The females were slightly more sensitive to effects of the test substance with regard to mortality, but there were no marked differences between males and females in the response to the test substance with regard to cytotoxicity and mutagenicity.