Interdiscip Toxicol. 2011; Vol. 4(3): 144–148. doi: 10.2478/v10102-011-0022-x Published online in: www.intertox.sav.sk & www.versita.com/science/medicine/it/ Copyright © 2011 Slovak Toxicology Society SETOX This is an Open Access article distributed under the terms of the Creative Commons Attribu- tion License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. interdisciplinary ORIGINAL ARTICLE Plasma and whole brain cholinesterase activities in three wild bird species in Mosul, IRAQ: In vitro inhibition by insecticides Ashraf S. ALIAS, Muna H. I. AL-ZUBAIDY, Yaareb J. MOUSA, Fouad K. MOHAMMAD Department of Physiology, Biochemistry and Pharmacology, College of Veterinary Medicine, University of Mosul, P. O. Box 11136, Mosul, Iraq ITX040311A03 • Received: 30 May 2011 • Revised: 21 July 2011 • Accepted: 03 August 2011 ABSTRACT Plasma and brain cholinesterase activities were determined in three wild bird species to assess their exposure to organophosphate and carbamate insecticides which are used in agriculture and public health. In the present study, we used an electrometric method for measurement of cholinesterase activities in the plasma and whole brain of three indigenous wild birds commonly found in northern Iraq. The birds used were apparently healthy adults of both sexes (8 birds/species, comprising 3–5 from each sex) of quail (Coturnix coturnix), collard dove (Streptopelia decaocto) and rock dove (Columba livia gaddi), which were captured in Mosul, Iraq. The mean respective cholinesterase activities (Δ pH/30 minutes) in the plasma and whole brain of the birds were as follows: quail (0.96 and 0.29), collard dove (0.97and 0.82) and rock dove (1.44 and 1.42). We examined the potential susceptibility of the plasma or whole brain cholinesterases to inhibition by selected insecticides. The technique of in vitro cholinesterase inhibition for 10 minutes by the organophosphate insecticides dichlorvos, malathion and monocrotophos (0.5 and 1.0 μM) and the carbamate insecticide carbaryl (5 and10 μM) in the enzyme reaction mixtures showed significant inhibition of plasma and whole brain cholinesterase activities to various extents. The data further support and add to the reported cholinesterase activities determined electrometrically in wild birds in northern Iraq. The plasma and whole brain cholinesterases of the birds are highly susceptible to inhibition by organophosphate and carbamate insecticides as determined by the described electrometric method, and the results further suggest the usefulness of the method in biomonitoring wild bird cholinesterases. KEY WORDS: biomonitoring; cholinesterase; insecticides; organophosphate; wild birds Introduction Inhibition of plasma or brain cholinesterase activity is a biomarker endpoint of exposure of wild birds to organo- phosphate and carbamate insecticides (Wilson, 1999; Cocker et al., 2002; Kwong, 2002; Wilson, 2005; Fildes et al., 2009). Organophosphate and carbamate insecticides are extensively used in public health, veterinary practice and agriculture (Coggon, 2002; Jaga & Dharmani, 2003). These insecticides induce muscarinic, nicotinic and central nervous system toxicoses in birds by inhibition of the target enzyme cholinesterase with subsequent accumulation of acetylcholine at the nerve terminals and neuromuscular junctions (Kwong, 2002; Rusyniak & Correspondence address: Fouad K. Mohammad, BVMS., MS., PhD. Department of Physiology, Biochemistry and Pharmacology, College of Veterinary Medicine, University of Mosul, P. O. Box 11136, Mosul, Iraq. TEL.: +964-770-160-5334 • E-MAIL: fouadmohammad@yahoo.com Nanagas, 2004; Wilson, 2005). Birds are naturally defi- cient in cholinesterase activity in erythrocytes. Therefore the diagnosis and monitoring of exposure to anticholin- esterase insecticides rely on the measurement of serum or plasma and brain cholinesterase activities in wild birds (Cairns et al., 1991; Burn & Leighton, 1996; Wilson, 1999; Iko et al., 2002; Claudie et al., 2005; Osten et al., 2005; Roy et al., 2005; Wilson, 2005; Fildes et al., 2009). The extent of cholinesterase inhibition and intoxication with the insecticides depends on factors such as the type of the insecticide, amounts the birds are exposed to, duration of exposure, frequency of exposure, route of exposure, species variation and the degree of environmental con- tamination (Osweiler, 1996; Wilson et al., 1998; Wilson, 1999; 2005; Wilson et al., 2005). We reported a simple electrometric method for measurement of blood or tissue cholinesterase activity in several animal species (for review see Mohammad, 2007) including the chicken (Al-Badrany & Mohammad, 2007; Mohammad et al., 2008) and wild birds (Alias &