Endogenous nitric oxide in the regulation of gastric secretory and motor activity in humans

Background: Studies in animals have shown that nitric oxide (NO) affects ga stric secretory and motor functions. However, little information is availab le about the involvement of this substance in the control of gastric secret ory and motor activity in man. Methods: This study, performed on 18 healthy, Helicobacter pylori-negative volunteers, was designed to evaluate the role of NO in the control of gastr ic acid secretion and of gastrin and somatostatin release in response to or dinary feeding (group A) and on gastric motor and electrical activity (grou p B). Gastric acid secretion was determined by means of intragastric pH-met ry before and after feeding with a semi-liquid meal. Plasma levels of gastr in and somatostatin were measured using specific radioimmunoassays. Gastric emptying rate was measured using the C-13-acetate breath test, antral moto r activity using a manometric catheter and myoelectric activity using cutan eous electrogastrography. Studies were repeated following pre-treatment wit h N-G-monomethyl-L-Arginine (L-NMMA), L-Arginine (L-Arg) or their combinati on. Results: L-NMMA delayed the recovery of intragastric pH to the pre-meal val ue, and suppressed postprandial gastrin release while increasing the plasma somatostatin level. L-Arg did not affect postprandial pH and plasma hormon es, but reversed L-NMMA-induced alterations in intragastric pH and in plasm a gastrin and somatostatin levels. Both postprandial antral motor activity (motility index) and gastric emptying significantly increased in tests with L-NMMA, but this was not observed when L-NMMA was given in combination wit h L-Arg or when L-Arg alone was used. The gastric electrical pattern, as me asured by cutaneous electrogastrography, was not affected by L-NMMA, L-Arg or their combination. Conclusions: (1) Endogenous NO appears to be involved in the regulation of postprandial gastric acid secretion. This effect may be mediated by the cha nges in release of gastrin and somatostatin. (2) Endogenous NO delays gastr ic emptying and antral motor activity without affecting gastric myoelectric al activity.