The Stretch-Activated Channel Blocker Gd3+ Reduces Palytoxin Toxicity in Primary Cultures of Skeletal Muscle Cells

Palytoxin (PLTX) is one of the most toxic seafood contaminants ever isolated. Reports of human food-borne poisoning ascribed to PLTX suggest skeletal muscle as a primary target site. Primary cultures of mouse skeletal muscle cells were used to study the relationship between Ca2+ response triggered by PLTX and the development of myotoxic insult. Ca2+ imaging experiments revealed that PLTX causes a transitory intracellular Ca2+ response (transient phase) followed by a slower and more sustained Ca2+ increase (long-lasting phase). The transient phase is due to Ca2+ release from intracellular stores and entry through voltage-dependent channels and the Na+/Ca2+ exchanger (reverse mode). The long-lasting phase is due to a massive and prolonged Ca2+ influx from the extracellular compartment. Sulforhodamine B assay revealed that the long-lasting phase is the one responsible for the toxicity in skeletal muscle cells. Our data analyzed, for the first time, pathways of PLTX-induced Ca2+ entry and their correlation with PLTX-induced toxicity in skeletal muscle cells. The cellular morphology changes induced by PLTX and the sensitivity to gadolinium suggest a role for stretch-activated channels.