BIOMARKER RESPONSES IN CYPRINIDS OF THE MIDDLE STRETCH OF THE RIVER PO, ITALY

Fish belonging to three species of cyprinids, that is, barbel (Barbus plebejus), chub (Leuciscus cephalus), and Italian nase (Chondrostoma s oetta), were collected from two sites of the River Po, located upstrea m and downstream from the confluence of one of its middle-reach pollut ed tributaries, the River Lambro. The two groups of individuals caught for each species were analyzed and compared for several microsomal an d cytosolic biochemical markers. The enzymatic activities assayed in f ish liver included ethoxyresorufin O-deethylase (EROD), aminopyrine-N- demethylase (APDM), uridine diphosphate glucuronyltransferase (UDPGT), glutathione S-transferase (GST), glutathione reductase, and glutathio ne peroxidase. In addition, the contents of reduced glutathione and no nprotein thiols were measured. Despite some differences among species, all microsomal activities (EROD, APDM, UDPGT) were found to be signif icantly induced in fish living downstream the River Lambro. With the e xception of a higher GST enzyme activity of barbel from the downstream reach, no significant modification was evident in any of the rested c ytosolic biomarkers. Results showed that barbel and nase better discri minated the two reaches of the River Po. In general, the alterations o bserved in feral fish are consistent with the results found in previou s studies conducted with rainbow trout (Oncorhynchus mykiss) under bot h laboratory and field conditions in the same middle reach of the Rive r Po. All of the data indicate that the downstream tract of the main r iver is exposed to the load of pollutants transported by the River Lam bro, including known inducers such as polychlorinated biphenyls and po lycyclic aromatic hydrocarbons (PAHs). The latter were analyzed in sed iments sampled at the two sites of fish collection, and the downstream sediment showed the highest concentrations of PAHs, although their le vels are comparable to those present in moderately polluted locations. Regardless of the site of exposure, barbel seem to be characterized b y more efficient antioxidant defenses. This observation could partly e xplain the lower prevalence of pathological lesions and parasites obse rved in this cyprinid in a previous study.