Figure 2.

Ion flows and potentials in intact skin. (A) Diagram of a typical epithelial cell in a monolayer with Na⁺ and Cl⁻ channels localized on the apical plasma membrane and K⁺ channels localized on the basolateral membranes along with the Na⁺/K⁺-ATPase. (B) This asymmetric distribution of ion channels generates a transcellular inflow of positive current that flows back between the cells. This positive current flow coupled to Cl⁻ movement in the opposite direction generates a transepithelial potential difference (TEP) of 10–60 mV. TJs between contiguous cells contribute to creating the TEP by providing high electrical resistance and preventing leakage of ions back down their concentration gradients between cells. Consequently, a concentration of positive charge exists behind the junctions at the deeper layers (positive sign in figure). The potential is, thus, relatively negative on the apical side of the junctions. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound