ANALYSIS OF INTRACELLULAR AND INTERCELLULAR CALCIUM SIGNALING IN A MOUSE MALIGNANT GLIOMA CELL-LINE

Intra- and intercellular calcium signaling in glioma cells was examine d by mechanical stimulation of a monolayer cell line of methylcholanth rene-induced mouse ependymoblastoma, 203-glioma, with a fine round tip glass needle. A fura-2 fluorescence image of the glioma revealed a fo ur- to eightfold increase in the cytosolic calcium ion concentration i n directly stimulated signal cells. The increased calcium spread to su rrounding cells at a speed of 20 mu m/sec for a distance of up to 200 mu m. Calcium was transmitted between adjacent cells and even in cells up to 200 mu m distant from the initially stimulated cell. Microinjec tion of Lucifer yellow dye showed no gap junctional communication betw een cells. Depletion of extracellular calcium ion inhibited both cytos olic calcium elevation and propagation to neighboring cells by mechani cal stimulus. An intracellular calcium blocker, TMB-8, eliminated the cytosolic calcium mobilization in a mechanically stimulated cell, but had no effect on calcium diffusion to surrounding cells. Nifedipine an d verapamil, antagonists of voltage-dependent calcium channels, did no t act on the mechanically induced calcium response. This suggests that some stimulating factor may trigger transmission of calcium, which ma y be ejected directly from single stimulated cells and mediated via a membrane receptor but not through a gap junction. The calcium signalin g in a mechanically stimulated cell may be related to both an influx a nd a redistribution of intracellular calcium from internal stores, whi le calcium propagation to neighboring cells may involve calcium influx alone.