THE EFFECT OF STAUROSPORINE ON CA2+ SIGNALS IN RAT BASOPHILIC LEUKEMIA (RBL-2H3) CELLS

We examined the effect of staurosporine on cytosolic calcium response in rat basophilic leukemia (RBL-2H3) cells using fura-2 as a fluorescent indicator of calcium ion. Staurosporine at a dose of 30 nM inhibited antigen-stimulated Ca2+-influx into the cells from the extracellular environment. In contrast, the drug at this concentration inhibited neither the mobilization of Ca2+ from intracellular stores nor inositol 1,4,5-trisphosphate (IP3) formation. At a high concentration (300nM), however, staurosporine completely inhibited the cytosolic calcium responses as well as IP3 formation. These results indicate that staurosporine, if used at an appropriate concentration, can be used to discriminate Ca2+-influx from extracellular environment from mobilization of the ion from intracellular stores. These results also suggest that protein kinases, possibly protein kinase C, are involved in the calcium influx of RBL-2H3 cells from the extracellular environment. Serotonin release was strongly inhibited by the drug at 30 nM staurosporine. Since the inhibition of serotonin release and suppression of cytosolic calcium increase in response to the antigen were in parallel, we concluded that the inhibition of serotonin release from RBL-2H3 cells caused by the drug was elicited by the suppression of Ca2+ influx into the cells.