Hepatotoxicity and immunotoxicity of MC-LR on silver carp.

Microcystins produced by some cyanobacteria can cause damages to the liver and kidneys of aquatic animals. In the natural water with cyanobacterial blooms, silver carp may suffer from the most serious affect of the bloom due to their filtering these cyanobacteria and ingesting them as food. In the present study, silver carp was exposed to microcystin-LR by using the method of intraperitoneal injection first to determine the acute toxicity of microcystin-LR on silver carp and then to determine the activity of inflammatory protein and content of inflammatory factors from the serum of silver carp following a subacute exposure of microcystin-LR at doses of 104.9 μg kg-1 (1/5 of LD50 ) or 262.1 μg kg-1 (1/2 of LD50 ). The results showed that MC-LR exposure increased fish liver index and promoted the activities of fish serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), indicating the hepatotoxicity of MC-LR on the fish. Moreover, MC-LR exposure also increased the number of leukocytes, complement C3 level, lysozyme activity (at the first 9 h of exposure), and the contents of cytokines TNF-α, IL-1β and IFN-γ in fish serum. In addition, a significant increase in IgM level was observed in the serum and head kidney of silver carp following MC-LR exposure. This result suggests that semi-lethal doses of MC-LR exposure is not only hepatotoxic but also immunotoxic to silver carp.