Assays for Dinoflagellate Toxins, Specifically Brevetoxin, Ciguatoxin, and Saxitoxin

Dinoflagellate toxins have been widely recognized as the compounds responsible for the human intoxications named paralytic shellfish poisoning (due to ingestion of saxitoxin and related compounds), neurotoxic shellfish poisoning (due to ingestion of brevetoxins), and ciguatera poisoning (due to ingestion of ciguatoxins). These toxins can accumulate in molluscs through filter feeding (saxitoxins and brevetoxins) or in fish through grazing and/or food-chain amplification (ciguatoxins), and are then passed on to humans through the ingestion of seafood. Each toxin binds specifically to a binding site (receptor) on the sodium channel of nerves, thereby either blocking or opening the channel (for structures of these toxins and their action on nerves, see Fig. 1). A result of this binding event is the impairment of normal nerve function, resulting in death in extreme cases. For this reason, it is important that accurate and sensitive assays for these toxins be made available. Two related types of assays, the radio-immunoassay (RIA) and the receptor binding assay, are very useful for detecting these toxins in a variety of matrices.