Antioxidant enzymes in the intramural nerves of the opossum
esophagus .
Thomas, R. M., S. Fang, L. S. Leichus, L. W. Oberley, J. Christensen,
J. A. Murray, A. Ledlow, J. L. Conklin.
Oakdale Gastroenterology Research Lab, Department of Internal
Medicine and The Radiation Research Lab*, University of Iowa College
of Medicine, and Iowa City Veterans Affairs Medical Center, Iowa
City, IA, 52242
APStracts 2:0161G, 1995.
Superoxide radical (O2.-) combines with nitric oxide (NO) to form
peroxynitrite, thereby nullifying the biological activity of NO.
Superoxide dismutase (SOD) prevents this reaction by converting O2.-
to H2O2. We tested the hypotheses that the antioxidant enzymes
catalase (CAT), manganese (Mn) SOD O2.- and copper-zinc (Cu/Zn) SOD
are present in enteric neurns of the opossum esophagus, and that O2.-
alters esophageal motor function. Immunostaining demonstrated CAT-,
Mn SOD-, and Cu/Zn SOD-immunoreactivity in interganglionic nerve
bundles and ganglia of the myenteric and submucosal plexuses. Western
blot analysis confirmed the presence of these enzymes in homogenates
of esophageal muscularis propria and enzyme assays demonstrated Cu/Zn
SOD and Mn SOD activities of 262 U/mg protein and 73 U/mg protein,
respectively. Both diethyldithiocarbamic acid (DDC), an inhibitor of
Cu/Zn SOD, and xanthine (X) with xanthine oxidase (XO), which
generate O2.-, shortened the latency of the nerve-mediated
contraction of circular esophageal muscle, the off-response, by 20.2%
and 23.4%, respectively. SOD alone did not affect the latency but it
inhibited the effect of X with XO on the latency. Cu/Zn SOD found in
intramural esophageal nerves may play a role in regulating NO
-mediated neuromuscular communication in the esophagus.
Received 16 November 1994; accepted in final form 20 July 1995.
APS Manuscript Number G451-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.