Solute transport across isolated epithelia

Abstract

The evidence obtained since the publication of Ussing's model indicates that diversity is one of the salient features of epithelial transport. The diversity is due not only to the variety of solutes transported, but also to the different mechanisms involved in transporting the same solute; nevertheless, it has been possible to establish some defined patterns of general importance. Although our ideas about the features of the individual components of the epithelial cells have been importantly modified and expanded since the proposal of Ussing's hypotheses, the notion of a two membrane system still remains the most successful scheme to explain the available evidence. Alternative models proposing a system in which a path that bypasses in some form the cell interior proper, although attractive, so far are less consistent with available facts.