EFFECT OF HYDROXYL RADICAL (OH-CENTER-DOT) ON SPHINCTER OF ODDI MOTILITY

Antioxidant enzymes are present in sphincter of Oddi nerves and regula te sphincter of Oddi motor function mediated by NO-releasing nerves. O xygen free radicals (O-2(radical anion)) produce hydrogen peroxide (H2 O2) by the action of superoxide dismutase (SOD). Hydroxyl radical (OH. ) has been shown to play an important role as a mediator of H2O2 toxic ity. The aims of our study were to determine the effects of H2O2 On sp hincter of Oddi motility and if these effects are mediated by OH.. Adu lt opossums were sacrificed and the sphincter of Oddi removed and plac ed in a tissue bath containing oxygenated Krebs solution. Force transd ucers recorded tension in a transverse orientation at two sites along the sphincter of Oddi specimen. H2O2 was added into the tissue bath at concentrations from 0.01 to 0.5%. O-2(radical anion) radicals were in hibited by the addition of SOD, while OH. was scavenged by the additio n of alcohol (ETOH) or dimethyl sulfoxide (DMSO). H2O2 produced a dose -dependent increase in baseline amplitude, frequency, and peak amplitu de of contractions. The effect of 0.01% H2O2 on sphincter of Oddi cont ractile frequency was inhibited by 0.2% ETOH and DMSO, but not by SOD. We conclude that H2O2 has profound effects on sphincter of Oddi motil ity and that the actions of H2O2 are probably mediated through OH..