Correlated Changes in Membrane Potential and ATP Concentrations in Neurospora

Abstract

IN a variety of tissues, electrical events seem to be more closely associated with the active transport of ions and with metabolism than with the concentration gradients of ions per se. This is evident in the generation of some transepithelial potentials, for example in gastric mucosa¹; in the hyperpolarization of sodium-loaded (and pumping) nerve and muscle cells^2–4 and in the rapid depolarization produced by respiratory inhibitors in fungi, algae and higher plant cells^5–7. Such phenomena may be described in terms of the electrogenic ion pump which separates charges across the cell membrane, thus generating a potential gradient along which ions will move. What is not certain, however, is whether the energy for this particular mode of ion transport is provided by ATP—which clearly drives the neutral coupled pumping of ions in many tissues⁸—or comes more directly from electron transfer, as suggested by Conway's “redox pump” hypothesis^9,10. We have examined this question for the fungus Neurospora, in which the relationship between metabolic and electrical events seems particularly close.