Effect of L-arginine on lower oesophageal sphincter motility in man.

OBJECTIVE: Inhibitory responses of the lower oesophageal sphincter (LOS) are mediated via an L-arginine/nitric oxide (NO) pathway. L-arginine is known as the precursor of NO. We have studied the effect of intravenous L-arginine on LOS motility in man. DESIGN: Twelve healthy subjects participated in a double-blind, placebo-controlled randomized study. METHODS: We investigated the effect of continuous infusion of L-arginine (500 mg/kg body weight/120 min) in six subjects under fasting conditions. Six other subjects were studied under postprandial conditions. LOS pressure (LOSP), swallow-induced LOS relaxations and transient lower oesophageal sphincter relaxations (TLOSR) were measured with sleeve manometry combined with pH metry. The meal consisted of a carbohydrate-high fat meal. Blood samples were taken before and after administration of L-arginine or saline to determine plasma levels of amino acids, cholecystokinin and gastrin. RESULTS: Plasma levels of arginine and citrulline significantly (P < 0.05) increased during L-arginine infusion. L-arginine did not affect plasma hormone levels. Under fasting conditions, LOSP and TLOSR were not influenced by L-arginine. Ingestion of the carbohydrate-high fat meal significantly decreased LOSP. L-arginine did not significantly influence TLOSR frequency, either under fasting conditions or postprandially. CONCLUSIONS: These results suggest that in humans under fasting or postprandial conditions intravenous infusion of L-arginine does not influence LOS motility.