Measurement of ion fluxes across epithelia.

Epithelial tissues line all wet surfaces of vertebrate bodies. Their major function is directional transport of ions and water. Cells forming an epithelial layer are bound together by a tight junction that forms a barrier to ion flux. Ions and water are transported via specialized molecules. The presence of a defect in a single ion channel molecule leads to cystic fibrosis - the most common, fatal, human genetic disease. The paper describes ion transport data obtained by means of different experimental techniques. Special attention is given to radiochemical tracers, transepithelial resistance determination, open circuit potential and short circuit current measurements, the nasal potential difference in healthy and cystic fibrosis patients, the use of ion selective electrodes, and electrochemical mapping of the cell membrane surface. The effect of different activators and blockers of ion transport molecules on measured parameters are also discussed.