CALCIUM ANTAGONISTIC ACTIONS OF TETRANDRINE DEPEND ON CELL-TYPES

We examined the effects of tetrandrine (TET) on Ca2+ mobilization in v arious types of cells using inositol trisphosphate-generating drugs an d compared it with those using the microsomal Ca2+-ATPase inhibitor th apsigargin (TG) which is a tool for analyzing Ca2+ store-regulated Ca2 + entry (capacitative Ca2+ entry). In rat pheochromocytoma PC12 cells, 100 mu M TET abolished high K+ (30 mM)-induced sustained increase in [Ca2+](i) and partially inhibited bradykinin (1 mu M)-induced or TG (1 00 nM)-induced Ca2+ entry. In NIH/3T3 fibroblasts, 100 mu M TET abolis hed Ca2+ entry induced by bombesin (1 mu M) or TG (100 nM). In rat gli oma C6 cells, the addition of 100 mu M TET reduced the sustained eleva tion of [Ca2+](i) induced by endothelin 1 (10 nM) or TG (100 nM) decli ning to the resting level. In rat parotid acinar cells, 100 mu M TET a bolished a sustained increase in [Ca2+](i) induced by carbachol (100 m u M) or TG (100 nM). In human leukemia T-cell line Jurkat, 100 mu M TE T did not inhibit Ca2+ entry evoked by the anti-CD3 antibody OKT3 (10 mu g/ml) or TG (100 nM). The present results suggest that the action o f TET on Ca2+ entry is dependent on cell types.