Molecular Physiology and Pathophysiology of Tight Junctions III. Tight junction regulation by intracellular messengers: differences in response within and between epithelia

Tight junction permeability differs with the type of permeants, their size, and their charge. Selective changes in permeability do occur, and they ill ustrate the diversity in functional reactions of tight junctions. This sugg ests that special structures in the tight junctions are involved. More and more structural components of the tight junctions are becoming known. The d ivergence in behavior of native tissue and filter-grown epithelial monolaye rs with respect to the effects of intracellular messengers offers the possi bility to relate structure and function. In addition to the tools for conve ntional permeability studies, probes have become available to detect change s in activation of intracellular effector proteins such as the protein kina se C isotypes, and with in situ imaging techniques the way is open for a fu nctional approach in the study of tight junctions.