Textbook Corrections are Required: Electro osmosis Causes Epithelial Fluid Transport, Not Osmosis

Abstract

The words (osmosis, electro osmosis) may be similar, but this hides a profound difference in mechanisms. In electro osmosis [1], an electric current carried by ions drives the fluid. In osmosis [2], a difference in concentrations of salt across a semipermeable membrane results in diffusion of the liquid in the direction of equilibrium. In the world of epithelia, the “driving force” for the mechanism of epithelial fluid transport always constituted one of the major mysteries. Towards the turn of the 20th century, all the other epithelial functions had been finally solved, except for fluid transport.