Studying the activation of epithelial ion channels using global whole-field photolysis

The production of saliva by parotid acinar cells is stimulated by Ca(2+) activation of Cl(-) and K(+) channels located in the apical plasma membrane of these polarized cells. Here we provide a detailed description of a flash photolysis experiment designed to give a global and relatively uniform photorelease of inositol 1,4,5-trisphosphate (InsP(3)) or Ca(2+) from caged precursors (NPE-InsP(3) or NP-EGTA) combined with the simultaneous measurement of whole-cell Ca(2+)-activated currents. The photolysis light source can be either an ultraviolet (UV) flash lamp or alternatively the output from a 375-nm diode laser, which is defocused to illuminate the entire field.