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secretion across
colonic epithelial cells
Departments of 1 Anesthesiology, 2 Physiology and Biophysics, and 3 Pediatrics, University of Alabama, Birmingham, Alabama 34294
We examined the effects of
H2O2
on Cl
secretion across
human colonic T84 cells grown on permeable supports and mounted in modified Ussing chambers. Forskolin-induced short-circuit current, a
measure of Cl secretion,
was inhibited in a concentration-dependent fashion when monolayers were
pretreated with
H2O2
for 30 min (30-100% inhibition between 500 µM and 5 mM).
Moreover,
H2O2
inhibited 76% of the Cl
current across monolayers when the basolateral membranes were permeabilized with nystatin (200 µg/ml). When the apical membrane was
permeabilized with amphotericin B,
H2O2
inhibited the Na+ current (a
measure of
Na+-K+-ATPase
activity) by 68% but increased the
K+ current more than threefold. In
addition to its effects on ion transport pathways,
H2O2
also decreased intracellular ATP levels by 43%. We conclude that the
principal effect of
H2O2
on colonic Cl secretion is
inhibitory. This may be due to a decrease in ATP levels following
H2O2
treatment, which subsequently results in an inhibition of the apical
membrane Cl conductance and
basolateral membrane
Na+-K+-ATPase
activity. Alternatively,
H2O2
may alter Cl secretion by
direct action on the transporters or alterations in signal transduction
pathways.
cystic fibrosis transmembrane conductance regulator; short-circuit current; T84 cells; sodium-potassium-adenosinetriphosphatase; potassium channels
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