Toxicological Effects of Hepatotoxins (Microcystins) on Aquatic Organisms

Some cyanobacteria produce microcystins, hepatotoxins with strong cytotoxicity mediated by inhibition of protein phosphatases. New evidence, however, suggests other toxic mechanisms, including oxidative damage and disruption of osmoregulation. Augmented levels of reactive oxygen species, lipid peroxides, and DNA damage were reported after microcystin exposure. The tripeptide glutathione (GSH) is one of the most important antioxidants, and it was reported that microcystin is conjugated with GSH. Microcystin conjugation could deplete the intracellular stores of GSH, leaving the cell more susceptible to oxidative stress. Inhibition of Na + , K + -ATPase by microcystin may be responsible for osmoregulation failure in freshwater fishes.