Research Article In Vitro Evaluation of the Genotoxicity of Acetamiprid in Human Peripheral Blood Lymphocytes Ays ó e Yavuz Kocaman 1 * and Mehmet Topaktas ó 2 1 Department of Biology, Natural and Applied Sciences Institute, C ¸ ukurova University, Adana, Turkey 2 Department of Biology, Faculty of Science and Letters, C ¸ ukurova University, Adana, Turkey Acetamiprid, a neonicotinoid insecticide, is com- monly used both in agriculture and domestic areas against a wide range of insects. The potential geno- toxicity of a commercial formulation of acetamiprid (Mosetam 20 SP, containing 20% acetamiprid as the active ingredient) on human peripheral blood lymphocytes was examined in vitro by sister chro- matid exchange (SCE), chromosomal aberrations (CAs), and micronucleus tests. Cells were treated with 25, 30, 35, and 40 lg/ml of acetamiprid for 24 and 48 hr. Acetamiprid induced SCEs and CAs significantly at all concentrations and treatment times and micronucleus formation was significantly induced at 30, 35, and 40 lg/ml of acetamiprid as compared with both the control and solvent control. Acetamiprid decreased the proliferation index (PI) at the two highest concentrations (35 and 40 lg/ml) for the 24-hr treatment period and only at the highest concentration (40 lg/ml) for the 48- hr treatment period when compared with the con- trol and solvent control. Peripheral lymphocytes exposed to all concentrations of acetamiprid showed significant decreases in mitotic index (MI) and nuclear division index (NDI) for both treatment periods when compared with both the control and solvent control. Furthermore, acetamiprid de- creased the MI in both treatment periods, and the NDI only in the 24-hr treatment period to the same extent as the positive control, mitomycin C (MMC). This study presents the first in vitro evidence for the genotoxicity of a commercial formulation of acet- amiprid in human peripheral lymphocytes. Environ. Mol. Mutagen. 48:483–490, 2007. V V C 2007 Wiley-Liss, Inc. Key words: acetamiprid; human peripheral lymphocytes; chromosome aberration (CA); sister chromatid exchange (SCE); micronucleus (MN) INTRODUCTION Neonicotinoids, which are the most important new class of pesticides, are used worldwide for crop protection and animal health care [Casida and Quistad, 1998; Yamamoto and Casida, 1999; Tomizawa and Casida, 2003]. Neonico- tinoids have begun replacing organophosphorus, organo- chlorine, and pyrethroid compounds as insecticides to control insect pests on major crops [Kovganko and Kash- kan, 2004]. These systemic insecticides are agonists of nicotinic acetylcholine receptors (nAChR) [Tomizawa and Yamamoto, 1993]. Neonicotinoid insecticides have signif- icant toxicity to insects but low toxicity to mammals because of the stronger affinity of neonicotinoids for insect nAChR than for mammalian nAChR [Liu, 1993; Tomizawa and Casida, 2003]. Acetamiprid, which is an insecticide belonging to the neonicotinoids class, has been used worldwide since the 1990s [Brunet et al., 2005] and is now being used in Turkey. The use of acetamiprid against a wide range of insects, both in agricultural and domestic areas, is very common [Horowitz et al., 1998; Turska and Wrobel, 1998]. Since the use of acetamiprid and other neonicotinoid insecticides (imidacloprid, thia- methoxam etc.) is steadily increasing, it is necessary to identify their possible effects on living organisms. A liter- ature review has shown that there are a few studies that have examined the genotoxicity [Zang et al., 2000; Feng et al., 2004, 2005; Karabay and Oguz, 2005] and carcino- genicity [Green et al., 2005a,b; Pastoor et al., 2005] of some neonicotinoid insecticides; however, the genotoxic *Correspondence to: Ay+e Yavuz Kocaman, Department of Biology, Natural and Applied Sciences Institute, C ¸ ukurova University, 01330 Adana, Turkey. E-mail: ayavuz@cu.edu.tr Grant sponsor: C ¸ ukurova University Research Fund; Grant number: FEF2003D20. Received 14 February 2007; provisionally accepted 28 February 2007; and in final form 12 April 2007 DOI 10.1002/em.20309 Published online 29 June 2007 in Wiley InterScience (www.interscience. wiley.com). V V C 2007 Wiley-Liss, Inc. Environmental and Molecular Mutagenesis 48:483^490 (2007)