Plasma Motilin Variation During the Interdigestive and Digestive States in Man

To evaluate the role of motilin in human physiology, we measured plasma motilin during the inter digestive and digestive states while recording antroduodenal contractile activity. In 24 healthy fasting subjects, 51 migrating periods of phase III activity were recognized, 42 of them started from the antral region and nine from the duodenum. A definite association was noted between circulating motilin and the gastric migrating motor complex. Significant peak elevations in plasma motilin were associated with phase Ills initiated from the antrum, but not with those originating from the duodenum. Exogenous synthetic motilin, when administered in supraphysiologic amounts, induced premature periods of front activity in fasting subjects. A test meal administered 30 minutes after a front of antral activity induced a significant release of motilin. Elevated plasma motilin levels were detected postprandially for a period of 30 minutes. Postprandial motilin increases were comparable in amplitude to the cyclic peak increases observed during the fasting period. Our study brings support for the argument that the contractile activity of the fasting stomach is regulated by circulating motilin in man, as it is in animals. The documented postprandial release of motilin is, however, unique to man and suggests that motilin could also be active during the digestive period in this species.