Chloride Electrochemical Potentials and Membrane Resistances inNitella translucens

Abstract

The chloride electrochemical potential difference between the inside of cells of Nitella translucens and the bathing medium has been measured by a direct electrical method employing Ag/AgCl electrodes. The membrane potential has been measured by means of conventional salt bridge microelectrodes. These data have been used to calculate the internal chloride concentration of the cells; the mean value obtained was 39 mM. This chloride electrochemical potential difference has been short-circuited thus causing an outward (depolarizing) electric current to flow through the cell membrane. The resulting membrane depolarization has been measured at two points along the length of the cell enabling the membrane resistance and space constant to be deduced; the respective values obtained were 24.8 KΩcm² and 3.0 cm. It is suggested that these experiments lend additional support to the hypothesis that during the action potential in the Characeae there occurs a transient increase in the chloride conductance of the plasmalemma.