Effects of oxygen radicals and radical scavenging on opossum lower esophageal sphincter.
Nitric oxide mediates esophageal peristalsis and lower esophageal sphincter (LES) relaxation. Superoxide produced with inflammation inactivates nitric oxide. Superoxide is cleared in biological systems by superoxide dismutase. We tested the hypothesis that superoxide and the superoxide scavenging system modulate LES function. Transverse strips of muscle from the opossum LES relaxed when stimulated by an electrical field. Diethyldithiocarbamite was used to inhibit copper/zinc superoxide dismutase. Xanthine and xanthine oxidase were used to generate superoxide. Xanthine with xanthine oxidase or diethyldithiocarbamite alone had no effect on the LES. However, xanthine/xanthine oxidase and diethyldithiocarbamite reduced LES relaxation 34.1% and increased its resting tone 71.2%. Superoxide dismutase did not affect LES function, but protected the tissue from the effects of diethyldithiocarbamite and xanthine/xanthine oxidase. These studies are consistent with the hypothesis that superoxide acts by inactivating nitric oxide and suggest that these antioxidant enzyme systems may play a role in the maintenance of LES function.
Leichus
L S
LS
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA.
Thomas
R M
RM
Murray
J A
JA
Conklin
J L
JL
D000818:Animals; D004050:Ditiocarb / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004943:Esophagogastric Junction / Q000187:drug effects / Q000502:physiology*; D005260:Female; D016166:Free Radical Scavengers / Q000378:metabolism*; D005609:Free Radicals / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009129:Muscle Tonus / Q000187:drug effects / Q000502:physiology; D009893:Opossums / Q000502:physiology*; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism*; D019820:Xanthine; D014969:Xanthine Oxidase / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
D016166:Free Radical Scavengers; D005609:Free Radicals; D014970:Xanthines; D013481:Superoxides; D019820:Xanthine; D004050:Ditiocarb; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase