Figure 3.

The Ussing Chamber can be used to measure ion transport between the two sides of an epithelial cell membrane by polarized cells. Here, a monolayer of epithelial cells separates two compartments. Fluid in the two compartments is identical to eliminate the contribution of passive paracellular diffusion driven by differences in concentration, osmotic pressure, or hydrostatic pressure. Voltage electrodes placed near the epithelial membrane maintain the potential difference at zero so that the current measured by the current electrodes reflects the movement of ions by active transport through the epithelial cells.