ABSTRACT
Okadaic acid (OA) and its congeners, the dinophysistoxins (DTXs), are polyethers belonging to the family of lipophilic phycotoxins. Microcystins (MCs) are heptapeptide toxins produced by cyanobacteria mainly proliferating in eutrophic freshwater systems. Although structurally different, both OA and MC inhibit serine/threonine protein phosphatases (PP) (principally 1 and 2A). However, whereas OA mainly inhibits PP2A and is less potent against PP1, MCs show equal inhibition potency against both PP1 and PP2A. Nevertheless, as a large number of congeners have been identifi ed, especially for MCs (more than 90 variants), the potency of PP inhibition may vary from one congener to another (Pereira et al. 2011). Whereas OA and the DTXs have been involved in acute human intoxications
French Agency for Food, Environmental and Occupational Health & Safety, Toxicology of Contaminants, Laboratory of Fougères, 10B rue Claude Bourgelat-Javené, CS 40608 35306 Fougères cedex, France. Email: valerie.fessard@anses.fr
due to contaminated shellfi sh consumption, MC exposure may occur by different routes including ingestion, contact and inhalation. Moreover, the sources of MC contamination are broad, involving drinking and recreational waters, MC-accumulating organisms in the food web as well as blue-green algae dietary supplements (Chorus 2001, Donohue et al. 2008). Therefore, chronic exposure may be more crucial for MCs than for OA/the DTXs. In this chapter, the data presented mainly focuses on OA and MC-LR (L=leucine and R=arginine), which are the most widely-investigated toxin congeners, and only addresses their effects on vertebrates, principally mammals, except in cases where relevant information obtained on non-mammalian systems may help promote understanding.
