Extracellular ATP is a potential neurotransmitter. It activates many types of cells, but its mechanism is unknown. Dr. Talamo has found that extracellular MgATP elevates cytoplasmic calcium levels in rat parotid cells through a novel mechanism. In the proposed studies, she will compare ATP and muscarinic effects to study how calcium levels and ion secretion are regulated. Her preliminary evidence indicates that ATP may not act through inositol-phosphate intermediates, and that ATP and muscarinic agonists regulate calcium and Na flux through different routes. To evaluate the role of phospholipase C activation in elevating cytoplasmic calcium levels, she will quantitate the time course of formation of (3H)-inositol phosphate metabolites and diglyceride for ATP and carbachol. Using the intracellular fluorescent indicator quin2 to monitor intracellular Ca++, and radiotracer ions to measure ion flux, she will explore the requirement for extracellular calcium and elevated intracellular calcium to activate Na, K and Cl transport. These studies will advance our knowledge of how ATP may activate many different types of cells, and will be integrated with electrophysiological studies utilizing patch clamp technology to develop a model for the mechanism of ion and fluid secretion in epithelial cells.
