title: Voltage dependent potassium fluxes and the significance of action potentials in Acetabularia.
abstract: Membrane potential, Vm, and K+ (86Rb+) fluxes have been measured simultaneously on individual cells of Acetabularia mediterranea. During resting state (resting potential approx. -170 mV) the K+ influx amounts to 0.24-0.6 pmol-cm-2-s-1 and the K+ efflux to 0.2-1.5 pmol-cm-2s-1. According to the K+ concentrations inside and outside the cell (40:1) the voltage dependent K+ flux (zero at Vm = EK = -90 mV) is stimulated approx. 40-fold for Vm more positive than EK. It is calculated that during one action potential (temporary depolarization to Vm more positive than EK) a cell looses the same amount of K+, which leaks in during 10-20 min in the resting state (Vm = -170 mV). Since action potentials occur spontaneously in Acetabularia, they are therefore suggested to have a significant function for the K+ balance of this alga.
mesh_terms: D000076:Acetabularia / Q000502:physiology*; D000200:Action Potentials; D001693:Biological Transport, Active; D000460:Chlorophyta / Q000502:physiology*; D004553:Electric Conductivity; D007700:Kinetics; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism
chemical_list: D012413:Rubidium; D011188:Potassium