Continuous measurement of gastric nitric oxide production.

With the use of a double-lumen catheter, nitric oxide (NO) was dialyzed across a Gore-Tex membrane into a gas phase and subsequently analyzed on-line by chemiluminescence. This new technique for the continuous measurement of NO was evaluated bench-side and applied in the human stomach in vivo to measure the nonenzymatic formation of NO generated from nitrite in an acidic milieu. A linear relation (r2 = 0.991, P < 0.0001) between concentrations of NO in aqueous solutions (2.5-52.5 mM) and NO in the corresponding gas phases obtained by the dialysis technique (50-1,000 parts per billion) validated the present method for quantitative analyses of NO. Interassay and intra-assay coefficients of variation at all concentrations of NO for six experiments were < 5%. High intragastric concentrations of NO (in the micromolar range) were found during basal conditions. The requirement of both nitrite from the saliva and an acidic environment for NO formation is indicated, since depletion of saliva as well as acid neutralization greatly reduced gastric NO concentrations. Furthermore, large amounts of gastric NO were formed after intake of sodium nitrate. With the use of this technique, NO can be continuously measured with accuracy experimentally and clinically in any organ accessible to intubation.