CIGUATOXIN, EXTRACTED FROM POISONOUS MORAY EELS, CAUSES SODIUM-DEPENDENT CALCIUM MOBILIZATION IN NG108-15 NEUROBLASTOMA X GLIOMA HYBRID-CELLS

Measurement of intrarellular Ca2+ concentration ([Ca2+]i) in cultured mouse NG108-15 neuroblastoma x glioma hybrid cells, using the fluoresc ent probe fura-2, revealed that 5-25 nM ciguatoxin (CTX) increased [Ca 2+]i either in cells bathed in standard medium or after removal of ext ernal Ca2+ by a Ca2+-free medium supplemented with EGTA. Tetrodotoxin prevented the CTX increased [Ca2+]i suggesting that CTX-induced mobili zation of intracellular Ca2+ depends on Na+ influx through voltage-gat ed Na channels. CTX-induced Ca2+ mobilization prevented subsequent act ion of bradykinin (1 muM) suggesting that CTX stimulates the inositol 1,4,5-trisphosphate-releasable Ca2+ store.