Constitutive nitric oxide synthase isoforms account for gastric
mucosal nitric oxide overproduction in uremic rats.
Mendez1, Asuncion, Mercedes Fernandez4, Ysamar Barrios3, Ignacio
Lopez-Coviella1, Jose Luis Gonzalez-Mora2, Maria Del Rivero1, Eduardo
Salido3, Jaume Bosch4 and Enrique Quintero1.
(1) Unidad de Investigaci
APStracts 3:0242G, 1996.
To study, in the rat, whether renal failure enhances gastric mucosal
nitric oxide (NO) formation we measured: 1) in vivo NO concentration;
2) NO synthase (NOS) activity, content, and mRNA expression in
gastric mucosal homogenates of uremic and sham operated anesthetized
rats. Gastric mucosal NO release was measured by an electrochemical
technique. NOS contents were analyzed by Western immunoblots, using
specific monoclonal antibodies. Constitutive (Ca2+ dependent; cNOS)
and inducible (Ca2+ independent; iNOS) NO synthase activities were
assayed by following the conversion of L-[U-14C]arginine to [U14C]
citrulline. mRNA expression for the constitutive neuronal (ncNOS),
endothelial (ecNOS) and iNOS isoforms was determined by reverse
transcription polymerase chain reaction (RT-PCR). Under basal
conditions, gastric mucosal NO concentration was significantly
greater in uremic compared to control rats. This, was accompanied by
significantly greater gastric mucosal cNOS activity in uremic than in
control rats, whereas no differences were observed in iNOS activity
between both groups of animals. Moreover, total enzyme content and
the levels of gastric mucosal mRNA expression for ncNOS, ecNOS and
iNOS, showed no significant differences between uremic and sham
operated rats. These data confirm that, in the uremic rat, an
enhanced Ca2+-dependent NOS activity is responsible for gastric
mucosal NO overproduction, and suggest that the main regulatory
mechanism is not transcriptional but translational and/or
postranslational in nature.
Received 9 February 1996; accepted in final form 28 October 1996.
APS Manuscript Number G55-6.
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