In exocrine gland cells, stimulation of a variety of surface receptors initiates a Ca2+ signalling system through activation of a polyphosphoinositide-specific phospholipase C. One product of phospholipase C activity, inositol 1,4,5-trisphosphate ((1,4,5)IP3), signals the release of intracellular Ca2+. Release of intracellular Ca2+ is followed by entry of Ca2+ into the cell across the plasma membrane. The mechanism by which Ca2+ entry is regulated is not well understood, although it is clear that (1,4,5)IP3 plays an important role. One hypothesis suggests that Ca2+ entry is triggered by the depletion of intracellular Ca2+ stores by (1,4,5)IP3, a process termed 'capacitative calcium entry'. The purpose of these studies is to gain understanding into the processes controlling capacitative calcium entry in exocrine gland cells.