The Electrical Measurement of Chloride Fluxes in Nitella

Abstract

The chloride efflux from cells of Nitella olavata at rest and during an action potential was continuously monitored by a Ag/AgGl electrode which measured the concentration of chloride in a thin film of solution flowing over the surface of the cell. Changes in the concentration of chloride subsequent to the passage of an action potential were followed and permitted calculation of the change in the flux of chloride ion across the cell membrane. The cell wall offers appreciable diffusion resistance to chloride ion, the effective diffusion constant being less than 1 % of chloride diffusion in free solution. Resting fluxes of chloride were measured in these cells and averaged 3 pmole/cm2 sec. The extra efflux of chloride during an action potential averaged 114 pmole/cm2 impulse.