Efeitos do surfactante nonilfenol etoxilado em peixes : função cardiorrespiratória e histopatologia em Tilápia-do-Nilo, Oreochromis niloticus, em condições de normóxia e hipóxia aquáticas

Abstract

Nonylphenol ethoxylate (NPE) is a nonionic surfactant component of many chemical formulations. Investigations on the effects of nonylphenol ethoxylate toxicity and its derivatives on fish mostly focus on endocrine disruption, genotoxicity, oxidative stress, bioaccumulation and mortality. However, exposure to these compounds can cause further damage, and the use of physiological and histological biomarkers is of great relevance, since it allows the identification of possible homeostatic disorders that may compromise the survival of these organisms. The objective of the present study was to analyze the cardiorespiratory responses and histological changes of Nile tilapia, Oreochromis niloticus, in a control situation and after 12h of an intraperitoneal injection of NPE9 (500 ng.kg-1 of body weight) submitted to gradual hypoxia. The exposure to NPE9 significantly increased the critical O2 tension (PcO2), reducing the ability to keep the metabolic rate (M ̇O2) constant, which may be related to the action of the compound on the functioning and structure of erythrocytes. Gill ventilation (V ̇G) increased significantly and progressively in both experimental groups in order to maintain M ̇O2 during graded hypoxia. The groups presented the same pattern of respiratory response, and increases in V ̇G were characterized by increases in ventilatory volume (VT), while respiratory rate (fR) remained constant. Although NPE at the concentration used in the present study was not sufficient to change O2 extraction from the ventilatory current (EO2) and heart rate (fH) during hypoxia. In addition, the exposure to NPE9 increased the frequency of melanomacrophagic centers in the liver and spleen, and it was possible to observe them in the ventricular myocardium. Together, the results of this study showed that exposure to NPE9 may compromise the survival of the species studied in hypoxic environments, but also indicate the need to include this compound in the legislation that regulates maximum permissible limits of substances in aquatic environments for the maintenance of life.