Nitric oxide and superoxide anion production during endothelial
cell proliferation.
Arnal, Jean-Fran[cedilla]cois, Ivan Tack, Jean-Paul Besombes, Bernard
Pipy, Anne N[grave]egre-Salvayre.
Laboratoire de Physiologie et INSERM CJF-9107, CJF-9206, U397,
U388, Institut Louis Bugnard, CHU Rangueil, 31054 Toulouse Cedex,
France
APStracts 3:0193C, 1996.
We have previously reported that NO (nitric oxide)-synthase activity,
protein and mRNA are increased in proliferating compared to post
-confluent bovine aortic endothelial cells (BAEC). As superoxide anion
inactivates NO, we have assessed in the present study the effect of
proliferation on superoxide anion production using cytochrome C
reduction. The superoxide anion production in proliferating cells was
increased about 3-fold compared to post-confluent cells in both basal
and calcium ionophore-stimulated conditions, and exceeded the amount
of released nitrite and nitrate (NOx) in all cases. A23187 1 [mu]M
stimulated the superoxide anion production about 2-fold at all stages
of confluency. Because superoxide anion can inactivate NO, we then
assessed the effect of proliferation on NO bioactivity released in
the conditioned medium, using RFL6 cells (reporter cells very rich in
guanylate-cyclase, which upon activation by NO generates cGMP, the
second messenger of NO). In the absence of added superoxide dismutase
(SOD) in the conditioned medium, the guanylate cyclase-stimulating
activities evoked by A23187 from proliferating and growth arrested
cells were similar, despite a greater NOx release in the former. When
SOD 100 U/ml was added in the conditioned medium, the guanylate
cyclase-stimulating activity evoked by A23187 1 [mu]M was increased
about 10-fold, and closely paralleled NOx release (i.e. was greater
in the supernatant of proliferating cells than in that of growth
-arrested cells). Thus, BAEC release more superoxide anion
extracellularly than NO at all stages of confluency. Endothelium
-derived superoxide anion is a major determinant of the breakdown of
NO.
Received 2 October 1995; accepted in final form 29 May 1996.
APS Manuscript Number C601-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96