Studying the Activation of Epithelial Ion Channels Using Global Whole-Field Photolysis

Abstract

The production of saliva by parotid acinar cells is stimulated by Ca²⁺ 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 (InsP₃) or Ca²⁺ from caged precursors (NPE-InsP₃ or NP-EGTA) combined with the simultaneous measurement of whole-cell Ca²⁺-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.