On the direction of the diffusional electric field in a mucous layer

A simple model of the mucous layer is used to illustrate the complex relationship of the diffusional electric field direction in the layer and parameters of the latter. It is shown that the field direction may depend not only on the ratios of mobile microion diffusivities but also on the characteristics of the layer (carboxylic group concentration and dissociation constant). The electric field direction is also shown to vary across the layer under appropriate conditions. The results are used to interpret the electrophoretic mechanism of the transport of macromolecules across the mucous layer on the surface of the digestive tract wall.