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).

The authors thank Dr Raymond J. Proudlock for his comments on their article. First, studies on the genotoxicity of lead salt are inconclusive. Pelclova et al. (1) did not detect a significant increase in structural aberrations (chromosome and chromatid exchanges, and breaks) in 22 workers from a lead battery plant. In contrast, Vaglenov et al. (2) found a significant increase in MN frequency among the lead-exposed staff (millers and assemblers) of a battery plant. The etiology of lead genotoxicity and carcinogenicity is complex. In vitro studies have demonstrated that lead interacts with proteins and nucleic acids, particularly at the sulfhydryl group and the phosphate backbone, respectively (3,4). Yang et al. (5) investigated the effects of lead acetate and found that lead may induce DNA damage through a Fenton reaction by interacting proteins. Lead ion has high affinity for the sulfhydryl groups of proteins. In our study, outbred female Wistar rats were treated by gavage once per week for 10 weeks with cumulative doses of 140, 250 and 500 mg/kg body weight of lead acetate (6). Because this study is a chronic study, peripheral blood is suitable for investigation. The results were compared with negative controls. Results were statistically significant. Studies have shown that mouse peripheral blood cells are an acceptable cell population for detecting micronucleated PCEs (MNPCEs) as long as the sampling schedule accounts for the release of newly-formed micronucleated erythrocytes from bone marrow to the blood (7,8). As indicated by Hayashi (9), cells should be intact and nuclei of nucleated cells and reticulum structure of reticulocytes should fluoresce strongly green and red. In our study, we considered these identifying features and PCEs were identified by their orange–red color, mature erythrocytes by their green color and micronuclei by their yellowish color. Those differences are shown in the paper. Several studies have shown a relationship between lead levels in blood and anemia (10,11). Gürer et al. (12) indicated that lead exposure causes mild anemia along with other haematological disturbances, including considerable variability in the sizes of RBCs (anisocytosis) and irregular shapes in RBCs (poikilocytosis). These data, considered in light of the data suggesting that lead induces oxidative stress in RBCs, support the hypothesis that lead-induced oxidative stress could, in part, be responsible for the lead-induced toxicity to the haematological system (12). There is a strong interaction between the formation of micronuclei and the antioxidant system. These systems vary among living organisms. In our study, we hypothesized that exposure to lead may have the potential for micronucleus formation. In order to understand the mechanisms responsible for the micronucleus formation further cytogenetic studies are needed.