Hyperpermeability and atp depletion induced by chronic hypoxia or
glycolytic inhibition in caco-2bbe monolayers.
Unno, Naoki, Michael J. Menconi, Andrew L. Salzman, Marianne Smith,
Susan Hagen, Yimin Ge, Robert M. Ezzell, and Mitchell P. Fink.
Department of Surgery, Beth Israel Hospital and Harvard Medical
School, Boston MA and Surgery Research Laboratory, Massachusetts
General Hospital and Harvard Medical School, Charlestown MA
APStracts 3:0028G, 1996.
Previous studies have documented that the barrier function of
epithelial or endothelial monolayers is deranged when cellular ATP
levels are rapidly decreased to very low levels by inhibitors of
mitochondrial and glycolytic function. We hypothesized that lesser
degrees of ATP depletion also might affect epithelial permeability,
particularly if the perturbation were sustained for a prolonged
interval. Using Caco-2BBe cells grown on permeable supports mounted
in bicameral chambers, we assessed permeability by measuring the
apical to basolateral clearance (flux divided by apical compartment
concentration) of fluorescein disulfonic acid. ATP was depleted by
incubating cells in glucose-free (Glu-) medium containing 10 mM 2
-deoxyglucose (2-DOG) for 12, 24, or 48 h or under an anoxic
atmosphere for 24, 48 or 72 h. Although both models of energy
depletion were characterized by significant derangements in barrier
function, metabolic inhibition with 2-DOG/Glu- resulted in greater
increases in permeability and more profound decrements in cellular
ATP content. Morphological studies using electron and confocal
fluorescence microscopy showed structural changes in individual cells
and derangements in the normal distribution of perijunctional actin
after monolayers were incubated with 2-DOG/Glu- but not after
incubation under an anoxic atmosphere. Addition of 10 mM lactic acid
(final pH 6.7) provided significant protection against both
hyperpermeability and ATP depletion induced by 2-DOG/Glu-. We
conclude that moderate degrees of ATP depletion are sufficient to
increase the permeability of Caco-2BBe monolayers and that lactic
acidosis helps to preserve ATP content, barrier function, and
morphologic integrity in hypoxic intestinal epithelial cells.
Received 1 August 1995; accepted in final form 29 November 1995.
APS Manuscript Number G327-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96