Abstract 9604432 Fewtrell The role of calcium in stimulus-response coupling in non-excitable cells is not well understood. The calcium responses of individual cells within a population are extremely diverse, often displaying marked oscillations in calcium, however little is known about the specific features of the calcium signal that are important for the functional response of the cell. In these studies the temporal relationship between changes in intracellular calcium and secretion will be studied at the single cell level in non-excitable cells, using a mucosal mast cell line as a model. The calcium responses of these cells have been well characterized and the exocytosis of secretory granules containing histamine, serotonin and other mediators by indo-1 photometry, and the secretion of serotonin containing granules will be monitored simultaneously in the same cell by constant potential amperometry. Thus the calcium response associated with a single exocytotic events or burst of secretion can be measured. Fluorescence imagining will monitor the calcium responses of a large number of individual cells simultaneously. The hypothesis that an increase in intracellular calcium is essential for exocytosis will be tested using a variety of stimuli to mast cell lines, cell clones and transfected cell lines. The requirement for protein kinase C activation and its role in modulating the secretory response will be re-examined at the single cell level. Information obtained about calcium signaling in mast cells will contribute to the overall understanding of the role and regulation of this important signaling molecule in many different cell types and systems. ***
