Joint effects of apoptosis induced by microcystins and bacterial lipopolysaccharides on grass carp (Ctenopharyngodon idellus) lymphocytes

In this study,grass carp( Ctenopharyngodon idellus) lymphocytes were used as the vitro test object to demonstrate the joint effects of microcystins( MC-LR) and bacterial lipopolysaccha-rides( LPS) on fish immune system. The results showed that MC-LR and LPS in the single and combined exposure groups could both induce grass carp lymphocytes apoptosis with typical ladderlike DNA electrophoresis characteristics. However,comparing the apoptosis rate of the combined and single exposure groups,it was suggested that bacterial LPS could cooperate with MC-LR causing a higher rate of fish lymphocytes apoptosis( 2. 1 and 3. 3-fold of that for the single exposure group Ⅰ( MC-LR) and Ⅱ( LPS),respectively),and there existed a significant dose-response relationship. The MC-LR cooperating with bacterial LPS decreased the activity of glutathione S-transferase( GST),increased the levels of intracellular reactive oxygen species( ROS) and malondialdehyde( MDA),resulted in DNA damage and cell arrest in G0 phase,which inhibited cell proli-feration and accelerated apoptosis. It was proved that MC-LR exacerbated fish immunotoxicity by collaborating with LPS,which had a serious adverse effect on aquaculture industry.