Use of Perna viridis as a Bioindicator of ParalyticShellfish Toxins at Low Pyrodinium bahamense varcompressum Density Using a Radioreceptor Assay

摘要

A radioassay method, i.e. the Receptor Binding Assay, was used for studying theuptake of Paralytic Shellfish Poisoning (PSP) toxins in the green bay mussel Pernaviridis highly consumed in the Philippines. This method allowed working at low celldensity of Pyrodinium bahamense var compressum (-102-103 cells/L) representativeof early stages of toxic algal blooms. The results indicated that within 16 hours toxiclevels of PSP are reached in the tissues of P. viridis, confirming the suitability of thegreen mussel as an indicator organism for paralytic shellfish toxicity in bivalvesduring the early stages of the bloom. Results also demonstrated that the weight-specific toxicity significantly increased with mussel size reduction. This method, basedon the competition between the labeled and unlabeled toxin for the sodium channelreceptor, offers better sensitivity than the mouse bioassay method. With an increasingamount of toxins in the sample, the amount of radiolabeled toxin binding with thereceptor decreases. The amount of radiolabeled toxin (tritiated saxitoxin) is thenmeasured using liquid scintillation counting. Quantification is based on a competitioncurve established by measuring competitive binding on a rat brain membrane withknown concentrations of saxitoxin.