OBJECTIVES: Cyanobacteria are producers of potent and environmentally abundant microcystins, representing an emerging global health issue. In the present study, we investigated the impact of pure microcystins and cyanobacterial biomass on laboratory rats (Wistar albino rats, males, 30 days old) under different exposure scenarios. METHODS: The rats were fed diets containing fish meat with microcystins in various concentrations and forms (cyanobacterial biomass and isolated microcystins) for 28 days. RESULTS: Although considerable amounts of microcystins (MCs) were administered to the rats, all levels of MCs in the liver were close to the detection limit (3-5 ng/g fresh weight) using liquid chromatography - tandem mass spectrometry. Only rats exposed to cyanobacterial biomass had clearly higher hepatic and splenic somatic indexes while markers of oxidative stress (glutathione-S-transferase, glutathione reductase, lipid peroxidatio) were significantly increased in the group exposed to the high dose of MCs. Most of the analysed biochemical parameters did not show clear differences among groups. Levels of bilirubin and lipases were significantly increased only after exposure to cyanobacterial biomass and MCs, respectively. Considering microscopic findings in the liver, kidney, thymus, spleen and brain, histopathology was dominated by alterations in the hepatic parenchyma and renal cortical tubular system. CONCLUSIONS: The present study demonstrates that oral exposure to MCs and cyanobacterial biomass may induce biochemical and detoxification responses associated with damage to liver and kidneys and in the laboratory rat.

Department of Ecophysiology and Aquaculture Leibniz Institute of Freshwater Ecology and Inland Fisheries Berlin Germany

Department of Fishery and Hydrobiology Faculty of Agronomy Mendel University Brno Czech Republic

Department of Veterinary Ecology and Environmental Protection Faculty of Veterinary Hygiene and Ecology University of Veterinary and Pharmaceutical Sciences Brno Czech Republic

Research Centre for Toxic Compounds in the Environment Masaryk University Faculty of Science Brno Czech Republic

Veterinary Research Institute Brno Czech Republic

Cyanobacteria Microcystis aeruginosa Contributes to the Severity of Fish Diseases: A Study on Spring Viraemia of Carp