L-ARGININE NITRIC-OXIDE PATHWAY MODULATES GASTRIC-MOTILITY AND GALLBLADDER EMPTYING INDUCED BY ERYTHROMYCIN AND LIQUID MEAL IN HUMANS

There is recent evidence that nitric oxide, a soluble gas produced fro m L-arginine, is released by the smooth muscle cells and neurons of th e gastrointestinal tract where it exerts a myorelaxive action. However , little is known about the effects nitric oxide has on gastric and ga llbladder motility during the inter- and postprandial phases in man. W e therefore investigated the effects 200 mg/kg/hr L-arginine exerts on the gastric and gallbladder motility induced by 2 mg/kg erythromycin or a liquid meal in 21 subjects in a double-blind, placebo-controlled study. Gastric and gallbladder emptying were evaluated by sonography. Fasting antral motility was expressed as antral motility index (MI). I n fasting subjects, L-arginine administration determined a threefold i ncrease in plasma nitrite concentrations. Administration of erythromyc in caused a significant rise in the antral MI, which was inhibited by L-arginine (P < 0.05). Ingestion of a liquid meal also significantly i ncreased antral MI, but it returned to basal values 90 min after the e nd of the meal. Although L-arginine administration caused a significan t reduction in the antral MI (P < 0.05), it did not inhibit gastric em ptying. L-Arginine provoked an approximately 40% increase in basal gal lbladder volume, completely blocked erythromycin-induced emptying, and partially, but significantly, prevented the emptying induced by a liq uid meal (P < 0.01). Our study suggests that nitric oxide may be impli cated in the physiological modulation of gastric and gallbladder motil ity during the inter- and postprandial phases in man.