Studies on Electrogenesis under High K+ Concentrations in Internodal Cells of Chara corallina

Abstract

concentration ([K+]o) on the membrane potential (Em) of Chara corallina was studied. Em more negative than -100 mV was maintained even at 100 mM [K+]o. Addition of Ca2+ to the external medium further increased this tendency. However, Em responded sensitively to the increase in [K+]o, when the electrogenic proton pump of the plasma membrane was inhibited by treating cells with dicyclohexylcarbodiimide, an inhibitor of proton pump. Analysis using equivalent circuit model of the plasma membrane suggested that the electrogenic proton pump was activated by the increase in [K+]o. In the presence of 100 mM K+, action potentials were generated by electric stimuli. The ionic mechanism of generation of action potentials in the presence of K+ at high concentration was discussed.