Ion-selective microelectrodes for intracellular measurements

Abstract

Ion-selective electrodes have been used for many years to analyze ion activities in electrolyte solutions. In recent years, these electrodes have been miniaturized and applied for measurements in the cell interior. This article describes basic principles for both the fabrication and the intracellular application of ion-selective microelectrodes, particularly focusing on double barreled liquid ion-exchanger microelectrodes. The use of ion-selective microelectrodes allows continuous and real-time measurements of intracellular ion activities of a single cell in both multicellular and isolated cell preparations under various conditions, such as changes in ion composition of the extracellular bathing fluid and exposure to certain drugs. With double-barreled ion-selective microelectrodes, the transmembrane potential and intracellular ion activities can be measured simultaneously in the same cell. Although there are still some problems or limitations to the intracellular application of ion-selective electrodes, this technique is useful for determining the actual movement of intracellular ions, and thereby to elucidate cellular mechanisms of membrane transport and other physiological functions.