Chemosphere 144 (2016) 1862–1868 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere Impact of an environmental relevant concentration of 17α -ethinylestradiol on the cardiac function of bullfrog tadpoles Raquel F. Salla a , Fernando U. Gamero a , Rafael Z. Rissoli a , Samuel E. Dal-Medico a , Luciano Mendes Castanho b , Cleoni dos Santos Carvalho a , Elaine C.M. Silva-Zacarin c , Ana L. Kalinin d , Fabio C. Abdalla c , Monica J. Costa a,∗ a Laboratory of Conservation Physiology, Department of Biology, Federal University of São Carlos, Rodovia João Leme dos Santos (SP-264), Km 110, Sorocaba, São Paulo, Brazil b Department of Morphology and Pathology, Pontifical Catholic University of São Paulo, Rua Joubert Wey, 290, Sorocaba, São Paulo, Brazil c Laboratory of Structural and Functional Biology, Department of Biology, Federal University of São Carlos, Rodovia João Leme dos Santos (SP-264), Km 110, Sorocaba, São Paulo, Brazil d Laboratory of Comparative Physiology and Biochemistry, Department of Physiology, Federal University of São Carlos, Rodovia Washington Luís (SP-310), km 235, São Carlos, São Paulo, Brazil highlights • Environmental relevant 17α-ethinylestradiol (EE2) concentrations alter the heart function of bullfrog tadpoles. • EE2 induced tachycardia, but did not change tadpoles’ activity level, pointing to its direct effect on the heart. • EE2 increased the cardiac force, which seems to be due to a PKA-dependent increase of transarcolemmal Ca 2+ influx. • EE2 elevated the cardiac energetic demand, reducing energy availability to other morphogenetic processes. • The lethargy can make the tadpoles more vulnerable to predators, as well less competitive for obtaining food. article info Article history: Received 30 July 2015 Received in revised form 30 September 2015 Accepted 10 October 2015 Available online 11 November 2015 Handling editor: James M. Lazorchak Keywords: 17α-ethinylestradiol Xenoestrogens Cardiac physiology Bullfrog tadpoles Lithobates catesbeianus abstract This study evaluated if a concentration of 17α-ethinylestradiol (EE2 – 10 ng L −1 for 96 h) normally found in Brazilian surface waters exerts any impact on cardiac function of bullfrog tadpoles (25 Gosner stage), Lithobates catesbeianus. During exposure, the animals’ activity level (AL -% of active individuals) was moni- tored twice a day. Then, the in loco heart rate (f H – bpm) was determined, as well as the relative ventricu- lar mass (RVM - % of body mass). Afterwards, cardiac ventricles were mounted for isometric force record- ings (CS – mN mm −2 ), and determination of the cardiac pumping capacity (CPC – mN mm −2 min −1 ). EE2 did not affect tadpoles’ AL, although it resulted in a tachycardia in animals exposed to EE2 (f H = 66 bpm) when compared to controls (f H = 52 bpm), suggesting that EE2 acts directly on the cardiac muscle of tadpoles, rather than being a result of an increased cardiac demand due to a higher activity level (i.e., avoidance response). Additionally, EE2 exerted a positive inotropic response, which resulted in a higher CPC, which occurred independently of an increase in the number of myofibrils of EE2-exposed animals, since RVM remained similar between experimental groups. Thus, the increase on cardiac demand induced by the exposure to EE2 elevates considerably the animal energy expenditure, diverting a large amount of energy that tadpoles could use for their growth and development. These alterations can make amphibians more susceptible to predators and reduce the likelihood to reach reproductive stage. © 2015 Elsevier Ltd. All rights reserved. ∗ Corresponding author. Universidade Federal de São Carlos, Departamento de Bi- ologia, Rodovia João Leme dos Santos (SP-264), Km 110, 18052-780 Sorocaba, São Paulo, Brazil. 3229-6001. E-mail address: monica@ufscar.br (M.J. Costa). http://dx.doi.org/10.1016/j.chemosphere.2015.10.042 0045-6535/© 2015 Elsevier Ltd. All rights reserved.