Calcium is permeable through a maitotoxin-activated nonselective cation channel in mouse L cells

The shellfish poison maitotoxin causes the irreversible opening of nonselective cation channels in mouse L cell fibroblasts, consistent with the action of this toxin in other cell types and the previously demonstrated existence of 28-pS voltage-insensitive nonselective cation channels that are activated by platelet-derived growth factor in these cells. Toxin-induced opening of these nonselective cation channels led to increases of intracellular calcium and secondary activation of a calcium-activated potassium channel. These effects were completely dependent on influx of extracellular calcium, supporting the conclusion that the maitotoxin- activated nonselective cation channels are permeable to calcium as well as to sodium and potassium. The implication of this finding is that calcium signaling through this channel underlies its links into the growth factor response.