The Toxicological Study Of Bound Microcystins

Microcystins are monocyclic heptapeptides produced by Microcystins aeruginosa. Recently, cyanobacterial bloom frequently occur in the eutrophic lakes, such as Dianchi Lake, Taihu Lake, Chaohu Lake and so on. Many reports demonstrate that microcystins can accumulate in aquatic products (fish, shrim, crab, snail, mussel) to a high level. But freshwater aquatic products are the important sources of animal protein in China. So microcystin contamination in aquatic products cannot be neglected. This thesis aimed at the safety of aquatic products by the toxicological study of GSH-LR and fish muscle-'bound MCLR. The main results were showed as following:1. The optimization of sample preparation for MC analysis in fish muscle.A modified method was developed for the determination of MC in fish muscle in the thesis. The muscle extract containing MC was enriched by SPE column, rinsed by 10% methanol-water solution, eluted by 100% methanol and detected by HPLC. The results showed that the ratio of methanol to water had great influence on the recovery of MC and the effect of impurities removal: lower than 10% methanol-water solution could not remove impurities effectively whereas higher than 20% methanol-water solution resulted in MC coelution with impurities, so 10% methanol-water solution was recommended to get better effects on the impurities removal and satisfied recovery of MC.2. The acute toxic study of GSH-LRAcute toxicity was examined in male mice which received MCLR(45μg/kg BW),low-concentration GSH-LR(45μg/kg BW), high-concentration GSH-LR (225μg/kg BW) and MCLR (45μg/kg BW) after preprojective of GSH (4mg/kg BW, 2h) via intraperitoneal injection. The results showed that the liver coefficient, the activities of ALT, AST, ALP, and the histopathology of liver were significantly different among treated groups (MCLR, high-concentration GSH-LR and MCLR after preprojective of GSH) and control group (p＜0.01), of which the MCLR group is the most significant. In contract, no significant changes were observed in low-concentration GSH-LR group except that the increase of liver coefficient and the activity of ALT and AST (p＜0.05) can be observed only at 2h and 4h after administration GSH-LR. Therefore, we concluded that the toxicity of GSH-LR was much lower than that of MCLR, but high-concentration GSH-LR could also lead to some extent adverse effect in mice even if the toxicity of high-concentration GSH-LR was still lower than that of MCLR (45μg/kg BW).3. The subchronic toxic effects of fish muscle-bound MCLRSubchronic oral gavage toxicity of MCLR in water and in fish muscle was examined in male Balb/C mice for 13 weeks to assess the safety of aquatic products. The results showed that the liver coefficient (p＜0.05) , the activities of ALT and AST (p＜0.01) increased significantly and distinct centrilobular to midzonal hepatucellular occurred after oral gavage of dissolved MCLR at a dose of 68.75μg/kg BW, but neither influence on the activities of BUN and Cr nor histological changes on kidney were observed at any time point. In contrast, the administration of fish muscle-bound MCLR at the same dose resulted in no obvious subchronic toxicity in mice, except that the increase of liver coefficient (p＜0.05) and the activity of ALT (p＜0.01) can be observed only at the first week. It was concluded that the toxicity of fish muscle-bound MCLR was much lower than that of dissolved MCLR.