OBJECTIVE

To test the hypothesis that the duodenum is required to coordinate interdigestive insulin secretion with gastrointestinal motility and to determine whether duodenectomy alters the interdigestive cycles of plasma motilin and insulin levels and their relations to insulin secretion and motility.

METHODS

Adult mongrel dogs were chronically implanted with force transducers in the stomach, duodenum, and upper jejunum to monitor contractile activity. Eight healthy mongrel dogs were divided into control and duodenectomized dogs. Insulin secretion, gastrointestinal motility, and plasma concentrations of motilin during the interdigestive period were measured in normal and duodenectomized dogs.

RESULTS

After duodenectomy, no obvious phase III contractions were seen in the gastric antrum, but migrating phase III contractions were seen in the upper jejunum. The plasma motilin concentration did not fluctuate as it does in normal dogs, and remained low. After duodenectomy, insulin secretory cycles were not coordinated with either cycles of interdigestive motility or the plasma concentration of motilin. Exogenous motilin administration stimulated endogenous insulin release significantly compared with saline-treated controls. The contractile response of the stomach to exogenous motilin after duodenectomy was similar to that of intact dogs.

CONCLUSIONS

Duodenectomy disrupts the relation between cycles of both interdigestive gastrointestinal motility and insulin secretion. These effects of duodenectomy may be attributable to interruption of the duodenopancreatic neural connections, hormonal abnormalities, or loss of vagus-sensitive humoral factors. The duodenum, which stores motilin, seems to play an important role in the relations between gastric migrating motor complexes and the concomitant increase of insulin secretion in fasted dogs. The mechanism responsible for the effect of motilin in both duodenectomized and normal dogs may involve a cholinergic pathway.