Biotransformations, antioxidant system responses and histopathological indexes in the liver of fish exposed to cyanobacterial extract

Radiocystis fernandoi, a microcystin (MC) producer, has been common in cyanobacterial blooms in tropical regions. MC is a hepatotoxin that causes tissue damage and even death in animals, including humans; its detoxification process may involve biotransformation and activation of the antioxidant defense (AD) system. In this study, we evaluated the detoxification pathway, examined the AD system responses and determined the alterations and the organ histopathological indexes in the liver of tropical fish Hoplias malabaricus after acute and subchronic intraperitoneal exposure to MC. The crude MC extract of R. fernandoi had predominantly MC-RR and MC-YR. The detoxification process was activated by increasing ethoxyresorufin-O-deethylase (EROD) activity while glutathione S-transferase was inhibited. The activity of AD enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) decreased after acute exposure; the SOD-catalase system and the glutathione (GSH) level increased after subchronic exposure. The carbonyl protein (PC) level, lipid peroxidation (LPO) and DNA damage were unchanged after acute exposure, while PC unchanged, LPO decreased and DNA damage increased after subchronic exposure. Histopathological alteration indexes (Ialt ) differed between acute and subchronic exposure, but the histopathological organ indexes (Iorg ) indicate liver dysfunction in both exposure periods. We conclude that MC-RR and MC-YR induce different liver responses depending on time exposure and the AD responses after subchronic exposure may help to partially restore the liver function. This article is protected by copyright. All rights reserved.