STEREOSPECIFIC EFFECTS OF INTRADUODENAL TRYPTOPHAN ON PYLORIC AND DUODENAL MOTILITY IN HUMANS

Background: L-Tryptophan delays gastric emptying in animals to a great er extent than D-tryptophan, but none of the possible motor mechanisms responsible for this stereospecific effect have been evaluated. Metho ds: In 11 healthy volunteers antropyloroduodenal pressures were record ed in the fasted state with a sleeve/sidehole manometric assembly duri ng 20-min intraduodenal infusions (2 ml min(-1)) of isotonic L- and D- tryptophan (50 mM, pH5.7) and normal saline (pH 5.5), given in randomi zed order. Results: Intraduodenal L-tryptophan increased basal pyloric pressure (p < 0.05), whereas D-tryptophan had no effect. In contrast, L- and D-tryptophan both stimulated (p < 0.05) localized phasic pylor ic pressure waves, and there was no significant difference in the resp onses. The number of duodenal pressure waves was greater during infusi on of L-tryptophan than during D-tryptophan (p < 0.05). Conclusion: We conclude that intraduodenal tryptophan has stereospecific effects on pyloric and duodenal motility. Although the precise contribution of th ese differential effects to gastric emptying remains to be clarified, they may be partially responsible for the differences in gastric empty ing of D-tryptophan and L-tryptophan.