Does antioxidant response mediated by gills catalase of Petromyzon marinus, during trophic migration towards the sea, depends on their geographical origin?

Abstract

The sea lamprey Petromyzon marinus (Petromyzontidae) during its trophic migration towards the sea suffers dramatic alterations in metabolism which can generate reactive oxygen species (ROS), such as H2O2 that cause damages in proteins, nucleic acids, and lipids. These deleterious effects can be avoid by antioxidant enzymes such as catalase (CAT) and glutathione peroxidase (GPx) that convert H2O2 in water, preserving the usually reducing environment of the cell. The main goal of this study was to evaluate changes in stress markers of ammocoetes subjected to NaCl gradient up to 35 PSU, during 30 days in aquaria. Sampling occurred at the beginning of the sea lamprey downstream migration in three Portuguese river basins: Lima, Vouga and Mondego. The ammocoetes were transported live to the laboratory in appropriate life support conditions. Cytosol obtained by differential centrifugation of gills homogenates, prepared in 50 mM Tris-HCl pH 7.5, were used for determination of ROS, GSH and GSSG contents as well as CAT and GPx activities. The results show that ammocoetes from the Lima basin were those who exhibited lower content in ROS as well as CAT activity (p <0.01). The gills GPx activity which was significantly higher in juveniles from the Vouga basin, did not change (p <0.01) during the adaptation to salinity in all animals. However, it was detected a significant increase in gills CAT activity of juveniles from Vouga and Mondego rivers, a response that eventually contributed to the stabilization of intracellular reducing power (GSH/GSSG), which offset a significant increase in ROS content detected in the gills of these animals. So, it can be concluded that adaptation to salinity generates higher intracellular ROS levels in P. marinus juveniles from Vouga and Mondego basins, being the catalase the main H2O2-detoxifying enzyme, and that, apparently, this antioxidant response varies with the geographical origin of the sea lamprey juveniles