Gasoline effects on biotransformation and antioxidant defenses of the freshwater fish Prochilodus lineatus.

Biochemical biomarkers in the Neotropical freshwater fish Prochilodus lineatus were evaluated following acute exposures to the water-soluble fraction of gasoline (WSFG). Fish were exposed to the WSFG diluted to 5% in water (WSFG group) or only to water (Control group) for 6, 24 and 96 h and the gills and liver were removed for the biochemical analyses. Fish exposed to WSFG for 24 and 96 h showed significant increase in the activity of 7-ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST) both in liver and gills, pointing toward phase I and phase II biotransformation of the compounds present in the WSFG. The results also indicated the activation of antioxidant defenses in both the liver and gills after fish exposure to WSFG. The liver showed activation of catalase (CAT) and glutathione peroxidase (GPx) after 96 h exposure. An increase in hepatic content of reduced glutathione (GSH) together with decreased glutathione reductase (GR) activity was observed after 24 and 96 h of exposure to WSFG. In the gills, only catalase (CAT) activity augmented after 6 and 24 h of exposure and GSH content increased after 24 h of WSFG exposure. However, in both the organs, activation of the antioxidant defenses was not enough to prevent oxidative damage since they showed lipid peroxidation (LPO) at one of the experimental times: the liver after 6 h and the gills only after 96 h of exposure to WSFG. This may indicate better adaptation of the liver to longer exposures, starting from 24 h. As the gills are the first organ to be exposed to xenobiotics, the antioxidant defenses were triggered immediately upon exposure to WSFG and were able to prevent the occurrence of LPO during the initial times.