LACK OF VOLTAGE-OPERATED CALCIUM-CHANNEL IN RAT GLIOMA C6 CELLS

We examined whether rat glioma C6 cells have voltage-operated Ca2+ cha nnel (VOC) or not. The addition of high K+ did not affect the cytoplas mic Ca2+ concentration ([Ca2+](i)). in addition, BAY K 8644, a VOC ago nist, did not increase [Ca2+](i) even in the presence of high K+. Bomb esin (BBS), an inositol trisphosphate-generating drug, and thapsigargi n (TG), a microsomal Ca2+-ATPase inhibitor, increased [Ca2+](i), after which it decreased to a sustained, and still higher than original lev el. The addition of verapamil, diltiazem and nimodipine did not affect an increase in [Ca2+](i) induced by BBS and TG. The addition of SK&F 96365, a receptor-operated Ca2+ channel (ROC) blocker, reduced the sus tained increase in [Ca2+](i) induced by BBS and TG. The present result s suggest that VOC does not exist in rat glioma C6 cells and this cell line is a good model for investigating signal transduction via ROC as glial cells.