| Summary: | Ciguatoxins (CTXs) and CTX precursors are produced by several <i>Gambierdiscus</i> spp. These polyether toxins are associated to ciguatera fish poisoning (CFP). In addition to CTX, maitotoxins (MTX) and gambierol are also produced by these dinoflagellates. MTX mechanism of action is strictly Ca2+ dependent, since the toxin induces a massive cytoplasmatic Ca2+ entrance. However, CTX activates the voltage-dependent sodium channels and no relation with calcium fluxes has been showed. The aim of this work was to study the effect of both toxins in the cytoplasmic calcium levels in the SH-SY5Y neuroblastoma cell line by using the fluorescent probe Fura-2 AM. Two completely different calcium profiles were obtained. While, MTX induces a sustained dose-dependent increase in Fura-2 ratio, CTX produces a light increase in dye ratio. From MTX results a calibration curve concentration versus Fura-2 ratio was obtained where the toxin concentration of an unknown sample can be calculated. Then, the effect of four samples from <i>Gambierdiscus</i> cultures was studied and different calcium profiles were obtained. A high increase in Fura-2 ratio was observed in two samples. The calcium profile was similar to MTX and by using the calibration curve the amount of toxin was calculated (4.9 and 1.8 nM of MTX). In the other samples, from the Fura-2 results the presence of CTX like compounds can be established.
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