Ecotoxicology and Environmental Safety 59 (2004) 109–115 Dynamics of cytochrome P450 inducers in polluted sites of Sa˜o Paulo city reservoirs Thomaz A.A. Rocha-e-Silva, a Francisco T. Rantin, a Jose E. Matsumura-Tundisi, b Takako Matsumura-Tundisi, b Jose G. Tundisi, b and Igor A. Degterev a,c, a Department of Physiological Sciences, Federal University of Sa˜o Carlos, Rod. Washington Luı´ s, km 235, P.O. Box 676, 13650-905 Sa˜o Carlos, Sa˜o Paulo, Brazil b International Institute of Ecology, Rua Bento Carlos 750, 13560-660 Sa˜o Carlos, Sa˜o Paulo, Brazil c Department of Chemical and Biochemical Kinetics, Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin Str. 4, Moscow, Russian Federation Received 12 March 2002; received in revised form 6 May 2003; accepted 12 May 2003 Abstract The first analysis of water pollutants using biomarkers at the Guarapiranga Reservoir, which supplies water for one-third of the population of the Sa˜ o Paulo megalopolis (Brazil), is reported. Studies were performed before and after the start of water pumping to the Guarapiranga from the highly polluted Billings reservoir. Billings’s water was purified by passing through the natural wetland located near Guarapiranga. Liver enzymes of Oreochromis niloticus (tilopias) obtained from both reservoirs served as biomarkers of pollution in a comparison with animals obtained from a reference site. Enhanced levels of total cytochromes P450 (3.4 times) and b 5 (2.7 times) and activity of cytochrome c (P450) reductase (2.2 times) were observed in specimens collected near the water influx from the Billings before the pumping started. However, these parameters were significantly decreased 3 months later. This effect is probably due to dilution of pollutants because of the increased level of water in the Guarapiranga. r 2003 Elsevier Inc. All rights reserved. Keywords: Oreochromis niloticus; Bioindicators; Water pollutants; Induction; Cytochrome P450; Cytochrome b 5 ; EROD; Antioxidant enzymes 1. Introduction Measurements of biological changes induced by chemical contamination in aquatic environments may be useful in biomonitoring programs for detecting exposure to those chemicals (Troisi and Mason, 1997). The cytochrome P450-dependent mixed function oxyge- nase system of the vertebrate liver plays a crucial role in metabolism of foreign compounds, which, in turn, is of principal importance in the toxicology of natural and pollutant xenobiotics (Kezic et al., 1983). Toxic sub- stances affecting aquatic organisms contaminate some reservoirs of Sa˜o Paulo State, Brazil. This particularly concerns the Billings and Guarapiranga reservoirs, a hydrocomplex located in the south region of Sa˜o Paulo city. The Guarapiranga reservoir supplies water to nearly five million inhabitants of this city. The level of water in Guarapiranga sharply decreases during the dry season, and, thus, a pumping system to transfer water from highly polluted Billings to Guarapiranga was developed in 2002 to maintain the level of water in the latter reservoir. The pumping is performed through a wetland located between these two reservoirs. Studies of biological responses induced by pollutants in Brazilian waters are scarce. There are a few works dedicated to this problem concerning the Billings Reservoir (Bainy et al., 1996, 1999; Leita˜o et al., 2000), but, to the best of our knowledge, no such studies were performed in the Guarapiranga reservoir. Significantly higher levels of total microsomal cyto- chromes P450 and b 5 , as compared to control fish, were detected in liver and kidney of tilapia caught at the Billings reservoir. These findings were postulated to be associated with the presence of polychlorinated biphe- nyls (PCBs), also detected in these organisms (Bainy et al., 1996). Later, this was confirmed by Leita˜o et al. (2000), who also observed more than a 20-fold increase ARTICLE IN PRESS  Corresponding author. Present addres: International Institute of Ecology, Rua Bento Carlos 750, 13560-660 Sa˜o Carlos, Sa˜o Paulo, Brazil. Fax: +55-16-271-5726. E-mail address: vigordgt@power.ufscar.br (I.A. Degterev). 0147-6513/03/$-see front matter r 2003 Elsevier Inc. All rights reserved. doi:10.1016/S0147-6513(03)00097-6