Potassium channels and conductance in cultured mouse peritoneal macrophages

Recently interest has been growing in ionic membrane currents in macrophages as signals between membrane ligand interactions and cellular reactions such as phagocytosis and chemotaxis (1, 2). Most studies on mononuclear phagocytes, in which direct measurements of membrane potential or current were made, used glass microelectrodes as measuring probes (1). These electrodes have a very fine tip (0.1 µm), which punctures the membrane in order to establish an electrical connection with the inside of the cell membrane. However, the seal of the membrane around the microelectrode shank is not very tight, so that a shunt conductance results (3, 4). Such a shunt may obscure membrane potential and resistance changes relevant for macrophage functions (3).