Examining Ca2+ extrusion of Na+/Ca2+-K+ exchangers.

Na+/Ca2+-K+ exchangers (NCKX) are plasma membrane transporters that are thought to mainly mediate Ca2+ extrusion (along with K+) at the expense of the Na+ electrochemical gradient. However, because they are bidirectional, most assays have relied on measuring their activity in the reverse (Ca2+ import) mode. Herein we describe a method to control intracellular ionic conditions, and examine the forward (Ca2+ extrusion) mode of exchange of NCKX2.