[Interrelations between the presence or lack of bile and bile acids in the small-intestinal lumen, release of motilin and pancreatic polypeptide and migrating myoelectric complex in dogs]

Abstract

5 male and 1 female dogs weighing 15-20 kg were used in the study. Animals underwent the functional cholecystectomy, bidirectional cannulation of the common bile duct and the implantation of 9 bipolar electrodes located in the stomach and small intestine. In 13 experiments performed on 4 dogs the interdigestive myoelectric activity was recorded and plasma motilin and PP levels were determined by radioimmunoassay during: 1) the control period where the spontaneous bile circulation was preserved, 2) bile depletion with or without intravenous motilin (56 pmol.kg-1.hr-1) infusion, 3) intraduodenal infusion of 50 mM Na-taurocholate with or without intravenous infusion of PP (400 pmol.kg-1.hr-1). During 88 additional experiments performed on all operated animals, which comprised the control studies, bile deprivation experiments and bile or bile acid infusions, the interdigestive myoelectric activity was recorded along with the estimation of sites of phase III origin. Motilin infusion at the lack of bile and bile acids in the intestine elicited the premature phase III in the duodenum, markedly increased the percentage of phases III originating from the stomach, inhibited the arrival of phase I of the myoelectric cycle and lowered plasma PP level. Infusion of PP despite the presence of bile acids in the small intestinal lumen caused the phase III originated from the proximal or mild jejunum and lowered plasma motilin level. Thus, unlike bile or bile acids, both motilin and PP are directly responsible for the appearance of phase III in the stomach and proximal small bowel of the dog. The luminal bile appears only to play a mediatory role influencing the release of the hormonal peptides examined here.