Experimental and Toxicologic Pathology 62 (2010) 311–316 Nitric oxide synthase immunolocalization and expression in the rat hippocampus after sub-acute lead acetate exposure in rats Concepcio ´ n Nava-Ruı ´ z a,c , Mireya Alcaraz-Zubeldia b , Marisela Me ´ ndez-Armenta a , Paula Vergara d , Araceli Dı ´ az-Ruı ` z b , Camilo Rı ´ os b,Ã a Departamento de Neuropatologı´a, de Neurologı´a y Neurocirugı´a, Mexico D.F., Mexico b Departamento de Neuroquı´mica, Instituto Nacional de Neurologı´a y Neurocirugı´a MVS. Insurgentes Sur 3877 La Fama, Tlalpan, C.P. 14269, Mexico, D.F. Mexico c Universidad Auto´noma, Metropolitana, Doctorado en Ciencias Biolo´gicas, Mexico, D.F., Mexico d Departamento de Fisiologı´a, Biofı´sica y Neurociencias, Centro de Investigacio´n y de Estudios Avanzados del IPN, Mexico, D.F., Mexico Received 22 January 2009; accepted 28 April 2009 Abstract Interference with nitric oxide production is a possible mechanism for lead neurotoxicity. In this work, we studied the effects of sub-acute lead administration on the distribution of NOS isoforms in the hippocampus with respect to blood and hippocampal lead levels. Lead acetate (125, 250 and 500 ppm) was given via drinking water to adult male Wistar rats for 14 days. We determined blood and hippocampal lead levels by atomic absorption spectrophotometry. Antibodies against three isoforms of NOS were used to analyze expression and immunolocalization using western blotting and immunohistochemistry, respectively. Blood and hippocampal lead levels were increased in a dose- dependent manner in groups treated with lead acetate. We found diminished expression and immunoreactivity of nNOS and eNOS at 500 ppm as compared to the control group. No expression and immunoreactivity was observed in hippocampus for iNOS. The observed high levels of lead in the blood reflect free physiological access to this metal to the organism and were related to diminished expression and immunoreactivity for nNOS and eNOS. r 2009 Elsevier GmbH. All rights reserved. Keywords: Lead; Nitric oxide; Nitric oxide synthase; Neurotoxicity; Hippocampus; Rats Introduction Lead (Pb 2+ ) is a ubiquitous pollutant in the ecosystem and is recognized by toxic effects on several organs and systems, particularly the central nervous system during early development (Goyer and Clarkson, 2001; ATSDR, 2005). Lead poisoning is more common in children than in adults and is characterized by acute encephalopathy, persistent vomiting, ataxia, seizures, impaired consciousness and coma (Goyer and Clarkson, 2001; Papanikolaou et al., 2005). Multiple mechanisms may be involved in lead-induced neurotoxicity; one of the most important is the ability of lead to mimic or, in some cases, to inhibit calcium-mediated regulation of cell functions (Bressler and Goldstein, 1991; Goyer and Clarkson, 2001; Bridges and Zalups, 2005). Other mechanisms that may be involved in lead toxicity ARTICLE IN PRESS www.elsevier.de/etp 0940-2993/$ - see front matter r 2009 Elsevier GmbH. All rights reserved. doi:10.1016/j.etp.2009.04.006 Ã Corresponding author. Tel.: +52 55 56063822. E-mail address: crios@correo.xocl.uam.mx (C. Rı ´os).