Paracellular Channel at Tight Junction

TIGHT JUNCTION

Tight Junction Channel

Tight junctions have a variety of permeabilities for ions and small molecules. Two parameters are used to assess the property of tight junction pores.

A simple comparison between TER and Flux.

(1) ELECTRICAL CONDUCTIVITY (expressed as Resistance) :

- is defined as net current flow across a confluent cell monolayer.

- a result of ions moving from a "HIGHER" to a "LOWER" electrical potential.

- occurs in vivo due to transporters on plasma membranes of cells (vectorial transport).

- induced experimentally by voltage-clamp or current-clamp, creating a potential difference across the monolayer.

(2) FLUX (expressed as Permeability):

- is defined as net flow of ions across a confluent cell monolayer .

- a result of ions moving from a "CONCENTRATED" to a "DILUTE" environment.

- occurs in vivo due to transporters on plasma membranes of cells (vectorial transport).

- induced experimentally by placing different concentrations of ions on apical and basal sides of monolayer.