Role of bile in regulation of gut motility

Bile empties into the duodenum not only after a meal but also in the interdigestive state. In man, interdigestive biliary emptying is related to fasting motor activity, the migrating motor complex (MMC), in the stomach and small bowel and generally occurs during phase 2 preceding a gastroduodenal phase 3 activity (activity front). It seems that the main regulatory peptide to initiate phase 3 is motilin. During a period with 13 phase 3 activities of MMC, 18 episodes of gall-bladder emptying and 19 motilin peaks were observed. Such a peak of plasma motilin usually took place 25 +/- 11 min after onset of biliary emptying. In conclusion, data indicate that motilin is released to the circulation by the biliary output and induces phase 3 of MMC. The induced phase 3 propels bile acids along the gut to promote their absorption in the distal intestine. The choleretic action of recycling of bile acids may cause subsequent episodes of biliary emptying with motilin release by the action of the enterohepatic circulation of bile acids. In such a manner the MMC may be withheld as a recycling motility pattern.