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Effect of reactive oxygen species on NH4+ permeation in Xenopus laevis oocytes
Institut National de la Santé et de la Recherche Médicale Unité 467, Université Paris V, Faculté de Médecine Necker-Enfants Malades, 75730 Paris Cedex 15, France To investigate the effects of reactive oxygen species (ROS) on NH permeation in Xenopus laevis oocytes, we used intracellular double-barre...
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Published in: | American Journal of Physiology: Cell Physiology 2002-06, Vol.282 (6), p.C1445 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | Institut National de la Santé et de la Recherche
Médicale Unité 467, Université Paris V,
Faculté de Médecine Necker-Enfants Malades, 75730 Paris
Cedex 15, France
To investigate the
effects of reactive oxygen species (ROS) on NH
permeation in Xenopus laevis oocytes, we used intracellular
double-barreled microelectrodes to monitor the changes in membrane
potential ( V m ) and intracellular pH
(pH i ) induced by a 20 mM NH 4 Cl-containing
solution. Under control conditions, NH 4 Cl exposure induced
a large membrane depolarization (to V m = 4.0 ± 1.5 mV; n = 21) and intracellular
acidification [reaching a change in pH i
( pH i ) of 0.59 ± 0.06 pH units in 12 min]; the
initial rate of cell acidification (dpH i /d t ) was
0.06 ± 0.01 pH units/min. Incubation of the oocytes in the
presence of H 2 O 2 or -amyloid protein had no
marked effect on the NH 4 Cl-induced pH i . By
contrast, in the presence of photoactivated rose bengal (RB),
tert -butyl-hydroxyperoxide ( t -BHP), or
xanthine/xanthine oxidase (X/XO), the same experimental maneuver
induced significantly greater pH i and
dpH i /d t . These increases in pH i
and dpH i /d t were prevented by the ROS scavengers
histidine and desferrioxamine, suggesting involvement of the reactive
species 1 gO 2 and ·OH. Using the
voltage-clamp technique to identify the mechanism underlying the
ROS-measured effects, we found that RB induced a large increase in the
oocyte membrane conductance ( G m ). This
RB-induced G m increase was prevented by 1 mM
diphenylamine-2-carboxylate (DPC) and by a low Na +
concentration in the bath. We conclude that RB, t -BHP, and
X/XO enhance NH influx into the oocyte via activation
of a DPC-sensitive nonselective cation conductance pathway.
ammonium ions; nonselective cationic conductance |
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ISSN: | 0363-6143 1522-1563 |
DOI: | 10.1152/ajpcell.00410.2001 |