AJP - Gastrointestinal and Liver Physiology, Vol 272, Issue 5 1050-G1056, Copyright © 1997 by American Physiological Society
The role of antioxidant enzymes in the control of opossum sphincter of Oddi motility
J. J. Cullen, B. M. Herrmann, R. M. Thomas, S. Fang, J. A. Murray, A. Ledlow, J. Christensen and J. L. Conklin
Department of Surgery, University of Iowa College of Medicine, Iowa City 52242, USA.
Superoxide rapidly oxidizes nitric oxide (NO) to form peroxynitrite, thus
terminating the biological activity of NO. The aims of our study were to
determine if superoxide alters the motor function of the sphincter of Oddi
and to localize the antioxidant enzymes in the sphincter of Oddi.
Immunostaining was performed and enzyme activities were measured in the
sphincter of Oddi. In physiological experiments, force-displacement
transducers recorded tension in the spontaneously contracting sphincter of
Oddi and after electrical field stimulation (EFS) of precontracted
sphincter of Oddi. Superoxide was generated by the addition of xanthine
with xanthine oxidase, superoxide radicals were scavenged by the addition
of superoxide dismutase (SOD), and catalase or SOD was inhibited by
diethyldithiocarbamic acid. Immunostaining demonstrated SOD and catalase
immunoreactivity in ganglia situated at the serosal surface of the circular
muscle. Total SOD activity was 202 +/- 12 U/mg. Generation of superoxide or
inhibition of SOD increased the contractile frequency and decreased
relaxation after EFS. We conclude that superoxide alters sphincter of Oddi
motor function, and the presence of superoxide scavenging enzymes in
enteric plexuses suggests that they may regulate sphincter of Oddi
neuromuscular function by clearing endogenous superoxide.
