Atenolol induces changes in the swimming behavior and acetyl cholinesterase activity of Jenynsia multidentata fish

M. E. VALDES; D. A. WUNDERLIN; M. A. BISTONI

Guarapari

Congreso; XIII Congresdo Brasileiro de Ecotoxicologia; 2014

Sociedade Brasileira de Ecotoxicologia (SBE)

Pharmaceuticals are a class of emerging environmental contaminants found in several watercourses worldwide, particularly those receiving inputs from wastewater treatment plants (WWTP). In the Suquía River (Córdoba, Argentina) atenolol, a β-blocker used to treat heart diseases, was frequently found up to µgL-1 levels, downstream from the WWTP of Córdoba city (Valdés et al., 2014). Yet, atenolol effects on the biota are scarcely known. The objective of this work was to evaluate effects of atenolol on the swimming behavior of J. multidentata, a fish inhabiting Suquía river, as well as changes in the activity of acetyl cholinesterase (AchE), an enzymatic biomarker commonly associated with locomotion. Female adults of J.multidentata (0.5±0.2 g weight ; 29±2 mm standard longitude) were collected in a quasi-pristine area (Río Yuspe, Córdoba, Argentina), adapted to laboratory conditions at 21±1 ºC, 12:12 h light:dark photoperiod and fed once a day with commercial fish pellets. Fish were exposed 14 days to 0, 1 and 50 µgL-1 of atenolol in dechlorinated water (1L/fish; n=10 for behavioral tests; n=5 for enzymatic assays). Aquarium solutions were renewed every 48h and samples were taken for analysis of atenolol concentration in water before and after renewal. At the end of the exposure, fish were transferred individually to aquariums specifically designed for recording the swimming activity with a digital camera. Fish were familiarized with the aquarium during 2 min and their movements recorded for 10 min. Swimming behavior was evaluated measuring the total distance traveled along recorded time. The software package used was Any-Maze 4.96. After recording, fish were anesthetized and dissected. Fish brain, muscle and liver were shock-frozen in liquid nitrogen and kept at -80ºC until enzymatic extraction as reported by Cazenaveet al., (2006). AchE activity was measured in according to Ellmanet al., (1961) on protein weight basis (Bradford, 1976). LinearMixed Models (SPSS Statistics 17.0) were applied for statistical analysis. The measured concentrations of atenolol in aquarium water were: below limit of detection (LOD= 0.2ngL-1) for the control group; 0.9±0.1 µgL-1 and 62±2µgL-1 at starting time; 0.8±0.1 µgL-1 and 64±1 µgL-1 after 48h exposure. AchE activity was significantly inhibited in all organs/tissues analyzed with respect to the control group. Brain was the organ with most pronounced inhibition percentage at both atenolol levels used. AchE in muscle was inhibited at the higher concentration. These results would mean that acetylcholine in exposed fish is not degraded as fast as it is in the control group; so, nerve impulses keep the transmission for longer periods. Results from swimming behavior showed that total distance traveled was significantly higher in treated groups compared to controls. This alteration could mean that fish might be spending more energy in locomotion than they normally would, which in turn could represent a threat to the fish, since they could probably be more exposed to predators. Alterations in cholinergic neurotransmission and locomotion of J. multidentata females, exposed to environmentally relevant concentrations of atenolol during 14 days, present the first evidence of changes in fish exposed to environmental relevant levels of atenolol, raising questions on other probable alterations that could add ecological risk to this and other species inhabiting the polluted basin. The simultaneous presence of complex mixture of pharmaceuticals and other contaminants poses an additional risk that needs to be evaluated in future works.