INWARD-RECTIFYING POTASSIUM CHANNELS IN THE RABBIT SUPERIOR LACRIMAL GLAND

Inwardly rectifying currents have been described in a wide variety of cells including both excitable (e.g., skeletal and cardiac muscle) and non-excitable (e.g., renal distal tubule and retinal Muller) cells. In these tissues, they have been reported as having several physiological roles. First, the inward rectifier is involved in setting and stabilizing the resting membrane potential. Second, in some cells, e.g., glial cells,1 its function is to buffer transient increases in extracellular K+ concentration. Third, it may be involved in recycling K+ to prevent its accumulation in the cell in response to Na+-H+ exchange. In this process, extruding H+ from the cell increases intracellular Na+. As the Na+-K+ pump extrudes these Na+ ions, K+ ions accumulate. These K+ ions may then leave via the inward rectifier.2