Bile salt inhibition of motility in the isolated perfused rabbit terminal ileum.

The effects of bile on small bowel motility were studied in isolated, perfused rabbit terminal ileum. It was proposed that bile delivery into the distal ileum would inhibit ileal motor activity, by peptide YY (PYY) release and therefore the effect of luminal bile on motor activity was examined and PYY release measured. Luminal bile and taurocheodeoxycholic acid (10 mmol) inhibited ileal motor activity. Arterial infusion of venous effluents from a bile inhibited ileum suppressed motor activity in a second isolated ileum. This shows the presence of a humoral inhibitor of ileal motor activity. Luminal bile increased venous PYY concentrations (42.5 (8.5) to 502 (46.2) pmol/l; p < 0.01) and increased bile salt values (1.7 (0.36) to 88.6 (5.6) 10 mumol/l/l; p < 0.005). Arterial infusion of taurocheodeoxycholic acid at concentrations found in the venous effluent (100 mumol/l/l) suppressed motility (p < 0.001) but infusion of PYY at concentrations in the venous effluent (500.0 pmol/l) failed to inhibit motility. Furthermore, PYY antagonist, PYX 1, failed to reverse the bile induced inhibition of motility. Luminal bile salts inhibit terminal ileal motility and this is independent of PYY release. By slowing motility, bile salts may participate in their own absorption by the 'ileal pump' and in the 'ileal brake' mechanism.