Registration Dossier

Toxicological information

Genetic toxicity: in vivo

Currently viewing:

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
other: read across from analogue substance
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)

Data source

Reference
Reference Type:
other: publicy available data
Title:
Micronucleus (A31837) Completed
Author:
NTP
Year:
1995
Bibliographic source:
NTP

Materials and methods

Test guideline
Guideline:
other: NTP protocol
Principles of method if other than guideline:
Mouse Bone marrow micronucleus test employs 1 to 3 treatment of the chemical under study, administered at 24hour intervals. Normally five male animals per treatment (dose) group. Doses extend up to the maximum tolerated dose. The route of administration in these short-term tests is usually either intraperitoneal injection or oral gavage. Based on the cell cycle and maturation times of the erythrocytes, harvesting of the bone marrow usually occurs 24 hours after the last dosing; this interval is indicated in the data tables as "sample collection time."
At that time, about 50% of the erythrocytes in the bone marrow are immature, newly formed erythrocytes, and these are the cell types that are checked for presence of micronuclei. The animals are euthanized by CO2 inhalation and the femurs are removed.
GLP compliance:
no
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed

Test animals

Species:
mouse
Strain:
B6C3F1
Sex:
male

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
phosphate buffer saline
Duration of treatment / exposure:
72h
Frequency of treatment:
3 treatments at 24 hour intervals
Post exposure period:
24 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
39.02, 78.125, 156.25, 312.5, 625, 1250 and 2500 mg/kg
Basis:
actual ingested
No. of animals per sex per dose:
5 males per dose
Control animals:
yes, concurrent vehicle
Positive control(s):
cyclophosphamide
- Route of administration: gavage
- Doses / concentrations: 50 mg/kg

Examinations

Tissues and cell types examined:
polychromatic erytrocytes
Details of tissue and slide preparation:
The bone marrow is flushed from the femurs and spread onto slides. The slides are air-dried, fixed, and stained with a fluorescent DNA-specific stain that easily illuminates any micronuclei that may be present.
Typically, 2000 polychromatic erythrocytes (PCEs, reticulocytes; immature erythrocytes) are scored per animal for frequency of micronucleated cells in each of 5 animals per dose group. In addition, the percentage of PCEs among the total erythrocyte population in the bone marrow is scored for each dose group as an indicator of chemical-induced toxicity.

In non-treated healthy mice and rats, the %PCE in bone marrow is usually around 50-60%. If a chemical interferes with the production of erythrocytes in the bone marrow, then the %PCE in the bone marrow may decline from the typical normal level. Conversely, if erythrocyte production is stimulated by chemical exposure, then a higher percentage of immature erythrocytes may be observed.
Statistics:
A formal statistical analysis of the data is performed that includes a trend test, to determine if there is an overall increase across all doses in the frequency of cells containing micronuclei, and a pairwise comparison of each dose group to the corresponding control, to see if any one dose group is statistically
different from the control group in frequency of micronucleated cells.
Data are typically presented as the mean number of micronucleated cells per 1,000 cells for each treatment group. A positive trend test is one in which the P value is equal to or less than 0.025. For the slide-based micronucleus data, the micronucleus frequency in any dose group is considered significantly elevated over the control group if the P value is equal to or less than 0.025 divided by the number of chemical-treatment groups.

Thus, if the number of treated groups is 3, then the required pairwise P value is 0.008. This adjustment in the pairwise P value is a correction for multiple comparisons of the same data. In the short-term studies, tests that give positive results are repeated to confirm the response.

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Remarks:
trend P = 0.370
Vehicle controls validity:
valid
Positive controls validity:
valid

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
The substance was tested for Micronucleus assay (short term bone marrow, oral gavage) on mice and the results show that is negative.
Executive summary:

The substance was tested for Micronucleus assay (short term bone marrow) on male mice. The results show that no micronucleated cells are generated after exposure to the substance by oral gavage for 72hours.