How to Make and Use Double-Barreled Ion-Selective Microelectrodes

Abstract

This chapter describes the construction of the double-barreled electrodes and interprets the results in view of possible artifacts. A discussion of how double-barreled electrodes can be made with tip diameters small enough to produce no more damage than the finest single-barreled electrodes is presented, along with an assessment of the effect of artificially introduced leaks of K+, Cl-, Na+, and H+. Double-barreled ion-selective electrodes represent an improvement over an assembly of single-barreled electrodes and allow a continuous recording of the changes in the intracellular electrical and chemical potentials from the same cell. The two types of double-barreled electrodes discussed in the chapter are the K+- and Cl--sensitive microelectrodes in which the sensitive membrane is a liquid ion exchanger, and the Na+ and H+ electrodes in which the ion-selective membrane is made from glass. The properties of the electrodes can be optimized according to a set of arbitrary criteria, such as the requirement of an abrupt change in potential, when the electrode enters the cell. However, the results obtained and the physiological conclusions derived even with the best electrodes must be shown to be consistent in a variety of experimental situations. Additional experiments with inhibitors of active accumulation would be needed to substantiate such conclusions. © 1980, Academic Press Inc.