Biliary excretion of biochemically active cyanobacteria (blue-green algae) hepatotoxins in fish

Abstract

Previous reports demonstrated that microcystin and related cyanobacteria polypeptides are rapidly cleared from plasma and accumulate in liver tissue. In the present study, we have used their ability to inhibit protein phosphatases to show that these cyanobacteria hepatotoxins are excreted into the bile of experimentally poisoned rainbow trout. At various times after oral administration of hepatotoxic Microcystis aeruginosa, bile samples were analysed for microcystin content by methanol extraction and protein phosphatase assays. An inhibitory principle that specifically suppressed protein phosphatase activity was detected in all bile samples removed between 1 and 72 h after oral exposure to toxic algae. These results indicate that biochemically active microcystin molecules are excreted into the biliary tract of poisoned fish.

Sequential ultrastructural and biochemical changes induced in vivo by the hepatotoxic microcystins in liver of the phytoplanktivorous silver carp Hypophthalmichthys molitrix

“…Compared with rainbow and goldfish, the depuration rate of MCs is much higher in the liver of silver carp. Fischer et al (2000) suggested that two factors may contribute to the decrease in extractable microcystin: one is biliary excretion of MCs or its metabolites (Sahin et al, 1996), the other is the slow covalent addition of MCs to the catalytic subunit of PP and other thiol containing cellular proteins (Hitzfeld et al, 1999) e.g., glutathione (Kondo et al, 1996), which may contribute to the progressive necrosis of hepatocytes. In the present study, although approximately 99% of accumulated MC-LReq.…”

Effect of dietary cyanobacteria on growth and accumulation of microcystins in Nile tilapia (Oreochromis niloticus)

“…The food safety of those fish is still a big problem. Some researches found some fishes could depurate microcystins accumulated in the liver through biliary excretion (Sahin et al, 1996) and some fishes can degradate microcystins (Xie et al, 2004). Expanded researches should be focusing on the effect of chronic microcystins exposure on different fishes and food safety warrantee.…”

Renal accumulation and effects of intraperitoneal injection of extracted microcystins in omnivorous crucian carp (Carassius auratus)

“…It is well known that MCs are potent inhibitors of protein phosphatases 1 and 2A (MacKintosh et al, 1990;Toivola et al, 1994;Guzman et al, 2003) with liver as target organ. The high selectivity to liver is believed to be due to toxin uptake via bile acid carriers (Suchy, 1993;Sahin et al, 1996). Histopathological studies in both fish and mammals revealed serious lesions of the liver including rounding and separation of hepatocytes, disruption of hepatic cords, hepatocyte necrosis and degeneration, and severe intrahepatic hemorrhage leading to lethal hypolovemic shock or liver failure (Guzman and Solter, 2002;Li et al, 2003Li et al, , 2004Malbrouck et al, 2003;Handeland and Ostensvik, 2010).…”