[8] Optical measurement of membrane potential in cells, organelles, and vesicles

Publisher Summary Optical methods for measuring and monitoring membrane potentials (E m ) in cell, organelle, and vesicle suspensions have been widely used during the past decade to study many fundamental problems in cell physiology. The chapter focuses on specific systems including red blood cells and Ehrlich ascites tumor cells, neutrophils, lymphocytes, renal membrane vesicles, muscle, nerve axons, ganglia, and secretory tissue. The chapter discusses cellular electrophysiological problems, which are being studied by means of optical potentiometric indicators. The chapter describes the current methodology, presents illustrative protocols for the use of slow and fast dyes in red-blood-cell suspensions, and discusses various methods to relate optical potentiometric signals to millivolt values. At present, optical potentiometric indicators are best regarded as the qualitative or, in certain restricted applications, semiquantitative indicators of changes in E m.