Copper sulfate affects Nile tilapia (Oreochromis niloticus) cardiomyocytes structure and contractile function Ka ´tia Cristina de Andrade Waldemarin • Rosiane Nascimento Alves • Marcelo Emı ´lio Beletti • Francisco Tadeu Rantin • Ana Lu ´ cia Kalinin Accepted: 30 November 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Copper sulfate (CuSO 4 )is an inorganic chemi- cal product worldwide used as an algaecide and a fungicide in aquaculture and agriculture and being discharged into freshwater environments where it can affect the freshwater fauna, especially fishes. The impact of copper on fish cardiac function was analyzed in two groups of Nile tila- pias, Oreochromis niloticus (control group and group exposed to 1 mg l -1 of CuSO 4 for 96 h). Structural and ultra-structural changes were studied and related to per- turbations of the inotropic and chronotropic responses of ventricle strips. Fish of Cu exposed group did not show significant alterations in the medium diameter and in the percentage of collagen in the cardiac myocytes when evaluated through the light microscope. However, the ultrastructural analysis revealed cellular swelling followed by mitochondrial swelling. The myofibrils did not show significant variations among groups. Force contraction was significantly decreased, and rates of time to tension increase (contraction) and decrease (relaxation) were sig- nificantly augmented after copper exposure. The results suggest that the copper sulfate impairs the oxidative mitochondrial function and consequently alters the cardiac performance of this species. Keywords Cardiac myocytes Á Cellular swelling Á Copper sulfate (CuSO 4 ) Á Mitochondrial function Á Myocardial contractility Á Oreochromis niloticus Introduction Copper sulfate (CuSO 4 ) is an inorganic fungicide/algaecide worldwide used to control algae in lakes, pounds, reser- voirs (Karan et al. 1998; Varanka et al. 2001), swimming pools and industrial cooling systems (Pedrozo and Lima 2001), among others. It is also frequently used in aqua- culture to control phytoplankton and algae growth (Boyd 1990; Tucker and Robinson 1990). According to Brown and Rattigan (1979) and Mal et al. (2002), a copper con- centration of 1 mg l -1 is commonly used in the control of algae and vascular plants in aquaria and fish ponds. Moreover, CuSO 4 is used for therapeutic purposes, reduc- ing the incidence of fish endoparasites such as protozoa, trematodes, and external fungi and bacteria. In this case, the recommended CuSO 4 concentration varies, according to the disease, from 1 up to 100 mg l -1 (Pavanelli et al. 2008; Schlenk et al. 1999; Mitchell and Tully-Jr 2009). However, above a specific concentration, copper can be toxic to fish including cultured species such as salmonids, cyprinids and catfish (Wurts and Perschbacher 1994), and recommended concentrations for fish therapeutic purposes usually ranges from 0.05 to 1.0 mg l -1 (Lightner 1983; Boyd 1990).It is also used in agriculture as fungicide and biofertilizer (Dores and Freire 2001; Bolan et al. 2003). In these cases, the residual solution is eventually directed to the effluents. As a result, copper is a pollutant found worldwide in aquatic ecosystems at concentrations ranging from 0.04 to 294 lgl -1 or, in extreme conditions, up to 20 mg l -1 (Oliveira et al. 2008). K. C. de Andrade Waldemarin Á F. T. Rantin Á A. L. Kalinin (&) Laboratory of Zoophysiology and Comparative Biochemistry, Department of Physiological Sciences, Center of Biological Sciences and Health, Federal University of Sa ˜o Carlos– UFSCar, Via Washington Luı ´s km 235, Sa ˜o Carlos, SP 13.565-905, Brazil e-mail: akalinin@ufscar.br R. N. Alves Á M. E. Beletti Laboratory of Histology, Department of Morphology, Institute of Biomedical Sciences, Federal University of Uberla ˆndia, Uberla ˆndia, MG, Brazil 123 Ecotoxicology DOI 10.1007/s10646-011-0838-3