AJP - Gastrointestinal and Liver Physiology, Vol 241, Issue 4 275-G288, Copyright © 1981 by American Physiological Society
Barrier function of epithelia
D. W. Powell
The ability of an epithelium to prevent permeation of noxious agents has
not been well studied except in the gastrointestinal tract where exclusion
of H+ has clinical significance. This article reviews the permeation routes
across epithelia both as elucidated in the extensive electrophysiological
work done in recent years and as demonstrated in morphological studies. We
thus place concepts about gastrointestinal barrier function into the
framework of transport physiology. Both the permeability and
permselectivity of epithelial barriers are reviewed here. The effects of
physical agents (pressure and electric current), polyvalent cations,
organic compounds with both specific (channel blocking) and nonspecific
(detergent) membrane properties, cyclic nucleotides, microfilament-active
agents, and particularly H+ on both the barrier function (permeability and
permselectivity) and transport function of epithelia are considered. Based
on the available data, an important role for active Na+ transport in the
maintenance of the epithelial barrier function can be postulated.
