The cytoplasm of an Acetabularia cell is normally at a potential of about -170 mv relative to the external solution; the vacuole is also at this potential. Although there is strict flux equilibrium for all ions, the potential is more negative than the Nernst potentials of any of the permeating ions. Darkness, CCCP, low temperature, and reducing [Cl-]o by a factor of 25 all rapidly depolarize the membrane and inhibit Cl- influx. Some of these treatments do not inhibit the effluxes of K+ and Na+. Increasing [K+]o also depolarizes the membrane both under normal conditions and at low temperature; in the latter case the membrane is partially depolarized in normal seawater (low [K+]o) and in high [K+]o positive potentials of up to +15 mv are attained. It is concluded that the membrane potential is controlled by the electrogenic influx of Cl-, and also, at least in some circumstances, by the diffusion of K+. In addition, it is suggested that electrogenic efflux of H+ may be important in transient nonequilibrium situations. An Appendix deals with the interpretation of simple nonsteady-state tracer kinetic data.
Article| June 01 1970
The Membrane Potential of Acetabularia mediterranea
H. D. W. Saddler
From the Botany School, University of Cambridge, Cambridge, England.
Dr. Saddler's present address is Metra Consulting Group, Ltd., 23 Lower Belgrave Street, London, S. W. 1, England.
Received: September 15 1969
Online Issn: 1540-7748
Print Issn: 0022-1295
Copyright © 1970 by The Rockefeller University Press
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H. D. W. Saddler; The Membrane Potential of Acetabularia mediterranea . J Gen Physiol 1 June 1970; 55 (6): 802–821. doi: https://doi.org/10.1085/jgp.55.6.802
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