Nile tilapia (Oreochromis niloticus), liver morphology, CYP1A activity and thyroid hormones after Endosulfan dietary exposure Ana Maria Coimbra a,b, * , Anto ´ nio Figueiredo-Fernandes c,d , Maria Armanda Reis-Henriques a,b a ICBAS-UP-Instituto de Cie ˆncias Biome ´dicas Abel Salazar da Universidade do Porto, Largo do Prof. Abel Salazar n°2, 4099-003 Porto, Portugal b CIIMAR-UP-Centro Interdisciplinar de Investigac ¸a ˜o Marinha e Ambiental da Universidade do Porto, LETox-Laboratory of Environmental Toxicology, Rua dos Bragas 289, 4050-123 Porto, Portugal c UTAD-Universidade de Tra ´ s-os-Montes e Alto Douro, Apartado 1013, 5000-911 Vila Real, Portugal d CETAV-Centro de Estudos Tecnolo ´ gicos, do Ambiente e da Vida, Apartado 1013, 5000-911 Vila Real, Portugal Received 9 October 2006; accepted 10 July 2007 Available online 28 July 2007 Abstract Endosulfan is a worldwide used insecticide suspected to be highly toxic to aquatic organisms, including fish. Most of the available studies have focused in water exposures, although this pollutant can be transferred through food chain. Therefore, in the present study, the effects of Endosulfan on tilapia (Oreochromis niloticus), when administered through the diet. Fish were fed 21 days with diets con- taining 1 and 0.5 lgg À1 of Endosulfan, after which qualitative histological liver analysis showed that Endosulfan induced hepatocyte destruction, vessel endothelium rupture and increased melanomacrophages aggregates. To test lower environmentally relevant doses of Endosulfan could induce hepatic damage, as well as other negative effects, such as altered phase I metabolism and plasma thyroid hormone levels. Hence, tilapia were orally exposed to 0.1 and 0.001 lgg À1 for 35 days. Low environmentally realistic doses of Endosul- fan were still able to induce liver histopathological damage such as increased hepatocyte vacuolization and increased eosinophil granular cell aggregates. Liver cytochrome P450 1A activity, evaluated through ethoxyresorufin-o-deethylase (EROD), was enhanced in tilapia exposed to 0.001 lgg À1 , whereas the highest dose had no measurable effects in this enzyme activity. Fish exposed to 0.1 lgg À1 of Endo- sulfan had depressed T4 plasma levels. Overall, the results of the present study further demonstrate the toxic effects of Endosulfan in tilapia when administered in the diet at environmentally relevant concentrations, which indicates that in the field food chain transfer may also be an importance source of this pollutant. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Tilapia; Endosulfan; Thyroid hormones; Liver; EROD; CYP1A; Melanomacrophages; Eosinophil granular cell 1. Introduction Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexa- hydro-6,9-methano-2,4,3-benzo-o-dioxa-thiepin-3-oxide) is a chlorinated cyclodiene insecticide used worldwide in a large variety of crops and also as a wood preservative [1]. Agriculture runoff, irrigation waters and wetland applica- tions are the major sources of this contaminant to the aquatic environment [1,2]. Due to its use, this insecticide is widely disseminated, being present in most continents [2–6]. Endosulfan presence in water poses a threat to aqua- tic organisms and fish species are highly sensitive to the presence of this insecticide [1], with a 96 h LC 50 of 1.5 lgL À1 for Ictalurus punctatus and Pimephales promelas and of 1.2 lgL À1 for Lepomis macrochirus [7]. Most of the available studies dealing with the effects of Endosulfan in fish have used water exposure [1,8,9].A range of negative effects were reported such as 0048-3575/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.pestbp.2007.07.001 * Corresponding author. Present address: CIIMAR-UP-Centro Inter- disciplinar de Investigac ¸a ˜o Marinha e Ambiental da Universidade do Porto, LETox-Laboratory of Environmental Toxicology, Rua dos Bragas 289, 4050-123 Porto, Portugal. Fax: +351 22 339 06 08. E-mail address: anacoimbra@ciimar.up.pt (A.M. Coimbra). www.elsevier.com/locate/ypest Pesticide Biochemistry and Physiology 89 (2007) 230–236 PESTICIDE Biochemistry & Physiology