Nitric oxide-induced derangements in the permeability barrier of
cultured intestinal epithelial monolayers: effect of low
extracellular ph.
Unno, Naoki, Michael J. Menconi, Marianne Smith, Douglas E. Aguirre,
and Mitchell P. Fink.
Departments of Surgery and Anesthesiology, Beth Israel Hospital and
Harvard Medical School, Boston MA
APStracts 3:0240G, 1996.
Nitric oxide (NO x ) increases the permeability of Caco-2BBe
enterocytic monolayers. Many of the toxic effects of NO x are thought
to be mediated by the peroxynitrite anion (ONOO-), which under mildly
acidic conditions, can rearrange to yield an intermediate with
reactivity similar to toxic OH x . Accordingly, we assessed the
permeability of Caco-2BBe cells grown on permeable supports for 24 h
in media titrated to normal or acidic extracellular pH (pHo) with or
without the NO x donors, SIN-1 or sodium nitroprusside (SNP).
Incubation with 2 mM SIN-1 at pHo 6.8 or 0.6 mM SNP at pHo 6.5
increased permeability (apical-to-basolateral flux of fluorescein
sulphonic acid), whereas at pHo 7.4, permeability was unaffected by
these concentrations of NO x donors. Accumulation of NO2-/NO3- in
medium (index of NO x release) was not increased by incubation of
cells with SIN-1 or SNP under mildly acidic conditions. Under acidic,
but not control conditions, incubation with SIN-1 caused disruption
of perijunctional actin filaments as assessed by fluorescence
microscopy. At pHo 6.8 and 6.5 (but not 7.4), SIN-1 significantly
decreased intracellular levels of both ATP and glutathione (GSH).
Incubation with 5 mM deferoxamine or 500 uM ascorbic acid (ONOO-
scavengers) abrogated SIN-1-induced hyperpermeability. We conclude
that mild acidosis augments NO x -induced intestinal epithelial
permeability, possibly by promoting oxidant-mediated cytoskeletal
damage and/or ATP depletion.
Received 28 March 1996; accepted in final form 9 October 1996.
APS Manuscript Number G116-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996