Some Problems Associated with the Measurement of Electric Membrane Potentials

Abstract

To determine absolute electrical potentials across biological membranes precisely and reliably is very difficult. In many cases one may at best obtain approximative values based on assumptions which cannot be tested rigorously. From the foregoing, on the other hand, it is clear that some at least approximative information about electrical potential is extremely important for the study of membrane functions. Hence considerable efforts have been made to improve the technique in order to keep unavoidable errors small enough not do endanger major conclusions drawn concerning the system under investigation. The best way to obtain fairly trustworthy results at the present time may be to apply more than one independent method, so that the values of both may confirm each other. In the following the most important methods presently available to estimate membrane potentials are listed according to the underlying principle. Special emphasis is given to those methods applicable to single cells and subcellular organelles and vesicles. For more information, see the review by Rottenberg (1975).