Mutagenesis Advance Access originally published online on July 5, 2006
Mutagenesis 2006 21(4):265; doi:10.1093/mutage/gel026
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RE: The evaluation of micronucleus frequency by acridine orange fluorescent staining in peripheral blood of rats treated with lead acetate. (Mutagenesis, 20, 411–415, 2005)
Charles River Laboratories Preclinical Services Montreal Inc. Senneville, Quebec, Canada
In their paper in the November 2005 edition of Mutagenesis, Çelik et al. (1
) describe small increases in micronucleated cells following 7 weekly oral treatments with lead acetate and conclude that this is indicative of genotoxic effects. However, in the same paper, the authors describe the equivocal nature of earlier in vitro and in vivo experiments on lead salts as well as anaemia and increases in erythropoiesis in mammalian systems.
The authors do not discuss indirect mechanisms of micronucleus formation. In particular, micronucleated erythrocytes can be induced by administration of erythropoietins without any corresponding increase in bone marrow chromosome damage [e.g. (2)] presumably due to errors in enucleation or possibly decreased fidelity of DNA proof-reading in overstimulated erythroblasts. Earlier studies (3) demonstrated that bleeding and phenylhydrazine-induced haemolysis also cause increases in circulating micronucleated reticulocytes in the mouse, probably via the same mechanism. This is further discussed by Hamada et al. (4) in the context of six compounds, which gave exaggerated increases in micronucleated reticulocytes in the rat following multiple administration.
The results of the Çelik et al. study cannot yield any concrete conclusion regarding the genotoxicity of lead acetate, since the increases in micronuclei could be a consequence of chronic anaemia. Where anaemia is suspected, it may be appropriate to prepare bone marrow metaphase slides from the same animals for potential examination of chromosome aberrations as described by Albanese (5) so that genotoxicity can be confirmed by a second related endpoint.
Finally, Figure 1 of the Çelik et al. paper implies that the quality of smears, with adherent and overlapping cells, was not of an adequate quality for quantitative analysis. The supravital staining technique used by the international collaborative group (4) and described in detail elsewhere (6) allows identification of the stage of maturity of the reticulocytes and produces a uniform monolayer of cells.
 |
Notes |
|---|
*To whom correspondence should be addressed: Tel: +514 630 8254; Fax: +514 630 8230; E-mail raymond.proudlock{at}ca.crl.com
References
-
1. Çelik A., Ögenler O., Çömelekoglu Ü. (2005) The evaluation of micronucleus frequency by acridine orange fluorescent staining in peripheral blood of rats treated with lead acetate. Mutagenesis 20:411–415.
2. Yajima N., Kurata Y., Imai E., Sawai T., Takeshita Y. (1993) Genotoxicity of genetic recombinant human erythropoietin in a novel test system. Mutagenesis 8:231–236.
3. Steinheider G., Neth R., Marquardt H. (1986) Evaluation of nongenotoxic and genotoxic factors modulating the frequency of micronucleated erythrocytes in the peripheral blood of mice. Cell Biol. Toxicol. 2:197–211.[CrossRef][Medline]
4. Hamada S., et al. (2001) Evaluation of the rodent micronucleus assay by a 28-day treatment protocol: summary of the 13th collaborative study group for the micronucleus test (CSGMT)/Environmental Mutagen Society of Japan (JEMS)—Mammalian Mutagenicity Study Group (MMS)‘. Environ. Mol. Mutagen 37:93–110.[CrossRef][Web of Science][Medline]
5. Albanese R. (1987) The cytonucleus test in the rat: a combined metaphase and micronucleus assay. Mutat. Res. 182:309–321.
6. Proudlock R.J., Statham J., Howard W. (1997) Evaluation of the rat bone marrow and peripheral blood micronucleus test using monocrotaline’. Mut. Res. 392:243–249.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||