Ion permeability and strength of cell contacts: ion permeability and mechanical properties of cell contacts in small intestine epithelium.

The effects of several simple parameters (pH, concentration of bivalent cations, osmotic pressure, and temperature) on the ion permeability and mechanical properties of cell contacts have been investigated. It has been shown that the mechanical properties of a cell contact make it possible to describe it as a viscoelastic system. The main contribution to cell adhesion is made by the tight junction. Two populations of acidic centers have been identified on the cell membrane surface. One population interacts with bivalent cations to assure cell adhesion. The other population of weaker acidic centers regulating ion permeation is involved in the cell membrane's interaction of the repulsion type. An intimate correlation has been established between changes in passive transepithelial ion permeability and cell adhesion in response to changes in pH and in bivalent cation concentration. Such a correlation is possible if the tight junction is the principal contributor to the passive ion permeability and mechanical strength of the cell contacts.