Micronucleated polychromatic erythrocytes

Animals, usually rodents, are exposed to the test substance by an appropriate route, usually by gavage or by intraperitoneal injection. Each treated and control group must include at least five animals per sex. Positive controls should produce micronuclei in vivo at exposure levels expected to give a detectable increase over background. No standard treatment schedule (i.e., 1, 2, or more treatments at 24-h intervals) has been recommended. Three dose levels are generally used these should cover a range from the maximum to little or no toxicity. The erythrocytes are sampled from the bone marrow and/or peripheral blood of the animals. If bone marrow is used, the animals are sacrificed at appropriate times after treatment, the bone marrow extracted, and preparations made and stained. When peripheral blood is used, the blood is collected at appropriate times after treatment and smear preparations are made and stained. Preparations are analyzed for the presence of micronuclei. An increase in the frequency of micronucleated polychromatic erythrocytes in treated animals is an indication of induced chromosome damage. 

Genotoxicity inhibition. Hot water extract of the fmit, administered intragastrically to mice at a dose of 500 mg/kg, was active vs adriamycin-, cyclophosphamine-, procarha-zine-, and mitomycin-induced genotoxicity. Genotoxicity was measured hy the presence of micronucleated polychromatic erythrocytes in bone marrow... 

Chemical Induction of Micronucleated Polychromatic Erythrocytes in Mouse Bone Marrow Cells... 

What is the potential of a test article to produce clastogenic genetic damage as measured by induced micronucleated polychromatic erythrocytes (MPCE) in bone marrow cells ... 

PCE—polychromatic erythrocytes NCE—normochromatic erythrocytes MPC—micronucleated polychromatic erythrocytes 90 CD-I mice (or rats)... 

Chemical Induction of Micronucleated Polychromatic Erythrocytes in Mouse Bone Marrow Cells Carcinogenicity Assessment ICH S2A Specific Aspects of Regulatory Genotoxicity Tests for Pharmaceuticals and ICH S2B Genotoxicity A Standard Battery of Genotoxicity Testing of Pharmaceuticals 2 -4 4-8 15,000-25,000... 

NMRI male mice exposed to benzene at concentrations ranging from 1 to 200 ppm, exhibited a reduction in bone marrow cellularity (nucleated cells per tibia), a reduction in the number of colony-forming granulopoietic stem cells (CFU-C) per tibia, and an increase in frequency of micronucleated polychromatic erythrocytes (MN-PCE) that varied with dose and duration of exposure as explained below (Toft et al. 1982). Mice exposed continually (24 hours/day) to 21 ppm or more benzene in air for 4-10 days showed significant changes in all of the parameters. No adverse effects on hematological parameters were noted in mice exposed to 14 ppm benzene continuously for 1-8 weeks (Toft et al. 1982). 

In the micronucleus test, mice are given the test substance by intraperitoneal injection. Mice ai e killed 24 or 48 h after treatment and the femoral marrow cells are smeared on glass slides, fixed, stained and the numbers of micronucleated polychromatic erythrocytes and of micronucleated normochromatic erythrocytes are recorded. The numbers of micronucleated erjdhrocytes and the proportion of polychromatic erythrocytes relative to the total erythrocytes are evaluated by observing 1000 erythrocytes on the same slide. 

Isoprene is nonmutagenic in bacterial test systems. However, isoprene forms adducts of blood hemoglobin in mice and rats. Increases in frequency of sister chromatid exchanges in bone marrow cells and in levels of micronucleated polychromatic erythrocytes were detected. Based on these results, isoprene is expected to induce tumors at multiple sites in exposed mice. Developmental toxicity has been indicated in mice, including decreased fetal body weight and ossification these impacts were not noted in rats. 

According to the revised ICH S2R1 guidance, as a test for chromosome damage, either the analysis of chromosomal aberrations or the measurement of micronucleated polychromatic erythrocytes in bone marrow cells in vivo is appropri-... 

Interpretation. A significant increase in the number of micronucleated polychromatic erythrocytes or young reticulocytes is usually considered indicative of structural and/or numerical chromosome damage caused by exposure to a clastogenic and/or aneugenic substance. 

In the micronucleus test with HCA intraperitoneally administered to mice at doses of 20, 100, 500, 2,500, or 12,500 pmol/kg, HCA was found to increase the number of micronucleated polychromatic erythrocytes (Lee and Lee 2007). A commentary on this study noted that the route of administration (intraperitoneal instead of oral) and the use of DMSO as part of the treatment but not the control group were likely to produce results different than those seen after oral use of HCA (Lau et al. 2008). 

In the mouse micronucleus assay, some chromosomal aberrations were observed in mice orally administered 3.0 g/kg of an aqueous extract of tree peony, but not in mice that were administered 0.15 to 1.5 g/kg of the same extract. An increase in the number of micronucleated polychromatic erythrocytes was observed in mice administered 0.75,1.5, or 3.0, but not 0.15 g/kg of the same extract (Yin et al. 1991). 

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