Benefits and costs of microcystin detoxication

WIEGAND, C., CAZENAVE, J., WUNDERLIN, D.A.

Bergen, Norway

Conferencia; Sixth International Conference on Toxic Cianobacteria.; 2004

Zebrafish embryos have frequently been used for toxicological and detoxication studies of microcystins. Uptake of microcystin-LR has been proven in the embryos prior to opening of the mouth. Microcystins furthermore caused teratogenic malformations or delay in development. To prevent those malformations, detoxication enzymes, such as glutathione S tansferases are activated and detoxication of microcystins has been shown to start by conjugation to reduced glutathione (GSH). Cyanobacterial toxins additionally provoke oxidative stress, which may be directly caused by the cyanobacterial compounds, but may also be caused by the detoxication activities. Hydrogen peroxide was increased during exposure to microcystins, and the catalase was one of the antioxidative enzymes reducing the oxidative stress for the embryos. Detoxication- and antioxidative processes need physiological energy. During embryonic development, the zebrafish are complete dependent from their yolk. Feeding starts at day 5, which is after hatching. This additionally needed energy for detoxication processes can only be diverted from the yolk and thus it can not be used for growth and correct development. Heat capacity, measured by DSC (Differencial Scaning Calorimety), showed differences between exposed and control groups, thas pointing out that detoxication process might be responsible for the observed differences. In detail, exposed embyos showed significantly reduced amount of fat, carbohydrates wehree slightly lowered but the proteins, most important for embryonic development, were not changed.