EFFECTS OF OXYGEN RADICALS AND RADICAL SCAVENGING ON OPOSSUM LOWER ESOPHAGEAL SPHINCTER

Nitric oxide mediates esophageal peristalsis and lower esophageal sphi ncter (LES) relaxation, Superoxide produced with inflammation inactiva tes nitric oxide. Superoxide is cleared in biological systems by super oxide dismutase. We tested the hypothesis that superoxide and the supe roxide scavenging system modulate LES function. Transverse strips of m uscle from the opossum LES relaxed when stimulated by an electrical fi eld. Diethyldithiocarbamite was used to inhibit copper/zinc superoxide dismutase. Xanthine and xanthine oxidase were used to generate supero xide. Xanthine with xanthine oxidase or diethyldithiocarbamite alone h ad no effect on the LES. However, xanthine/xanthine oxidase and diethy ldithiocarbamite reduced LES relaxation 34.1% and increased its restin g tone 71.2%. Superoxide dismutase did not affect LES function, but pr otected the tissue from the effects of diethyldithiocarbamite and xant hine/xanthine oxidase. These studies are consistent with the hypothesi s that superoxide acts by inactivating nitric oxide and suggest that t hese antioxidant enzyme systems may play a role in the maintenance of LES function.