Modulation of Epithelial Permeability by Extracellular Macromolecules.
Lewis, Simon A., Jamie R. Berg, and Teri J. Kleine.
Department of Physiology and Biophysics, University of Texas Medical
Branch, Galveston, Texas.
APStracts 2:0005P, 1995.
ABSTRACT
Epithelia are sheets of cells joined together by tight junctions. This
geometry allows an epithelium to act as a barrier, i.e., restrict the movement
of substances between two compartments that it separates (typically 1
compartment is the blood) and also to actively and selectively transport
substances between the two compartments. It has been known for a number of
years that both the barrier and transport functions of epithelia can be
regulated by hormones and neurotransmitters, and this regulation is a central
component of plasma electrolyte and nonelectrolyte homeostasis. Less
appreciated is that these epithelial functions can be modified by
macromolecules other than neurotransmitters and hormones. These
macromolecules have been divided into the following categories: proteases,
cytokines, cellular constituents, nonbacterial xenobiotics, and bacterial
xenobiotics. Such macromolecules can alter epithelial transport and barrier
function by a number of different mechanisms. These include proteolysis of
epithelial ion channels and tight junctional complexes, conversion of ion
pumps into a nonselective cation channel, increase in epithelial membrane
permeability resulting in cell swelling and lysis, and up- or downregulation
of cellular second messenger systems that can alter ion transport capabilities
or prove cytotoxic to the cells. Finally, these modifications can be either
transient or chronic in nature and in many circumstances result in a
pertubation of the electrolyte and nonelectrolyte status of the host organism.
APS Manuscript Number P-0007-5.
Article publication scheduled July 1995 Physiological Reviews.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 16 May 1995.