Avaliação ecotoxicológica das águas do Rio Pirajibú por análises de biomarcadores em girinos de rã-touro, Lithobates catesbeianus (Shaw, 1802)

Abstract

In Sorocaba/SP, the Pirajibú river courses the industrial zone of the city, and receives the effluents discharge from several companies. This river is classified as class 2, according to the criteria defined by Brazilian environmental law (CONAMA nº 357/2005), and State of Sao Paulo environmental law (Decree nº 8468/1976). The classification, appearance and characteristics, indicates that Pirajibú water does not result in mortality to aquatic organisms, however, the sublethal or toxicological effects have not been studied yet. Considering this gap, the present study aimed to promote an ecotoxicological and water quality assessment of the Pirajibú river. To perform it, water collections were carried out in the river at upstream and downstream from the industrial zone. The water samples were subjected to analysis of physicochemical parameters. The ecotoxicological tests were carried out through the analysis of biomarkers in the liver of bullfrog tadpoles, exposed for 96 hours to the waters of the Pirajibú river. The biomarkers analyzed include reduced glutathione (GSH - tripeptide), glutathione peroxidase (GPx), glutathione S-transferase (GST), and the metabolites glucose, proteins and triglycerides. The metals and other physical chemical analyzes, indicated that the downstream of the industrial zone has a lower quality than the upstream point. Regarding the biomarkers analysis, the activity of the GPx enzyme was significantly lower in the upstream group (6.94 ± 0.99 nmol Nicotinamide Adenine Dinucleotide Phosphate - NADPH / min / mg protein) compared to the control (14.11± 4.88 nmol NADPH / min / mg protein), while GST had significantly higher activity in the downstream group (53.674 ± 11.47 nmol Tioéter / min / mg protein) compared to the control group (36.42 ± 7.98 nmol of nmol Tioéter / min / mg protein). In reference to others biomarkers, no significant changes were observed between the control organisms and those exposed to the waters of the Pirajibú river. This result demonstrated that exposure for 96 hours was not able to change most of the biomarkers evaluated, but not enough to rule out the potential of the waters of this river provide oxidative stress, and other sublethal effects in bullfrog tadpoles.