A Secretory Epithelium of the Small Intestine with Increased Sensitivity to Bile Acids in Irritable Bowel Syndrome Associated with Diarrhoea

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Abstract
Irritable bowel syndrome is occasionally associated with diarrhea (IBSD). The loss of fluid cannot be explained by abnormal intestinal motility, but may be due to a secretory disorder of the intestine. Since the large bowel has proved to be absorptively normal in IBSD, perfusion studies of the ileum and jejunum were performed on 6 patients and 10 normal subjects. Perfusates were isosmotic saline solutions containing 0-2.5 mmol/1 glycochenodeoxycholic acid (GCDC). Net movements of H2O and electrolytes, bidirectional fluxes of Na, K and Cl, and the transmural electrical potential difference (PD) were recorded simultaneously. In the normal ileum 1 mmol/l GCDC significantly stimulated absorption, while 1.5-2.5 mmol/l decreased absorption and evoked secretion of H2O and electrolytes. In IBSD ileal secretion occurred spontaneously during control perfusions. Absorption was facilitated at 0.25 mmol/l GCDC, while larger concentrations evoked profuse secretion. Increased plasma to lumen fluxes seemed responsible for the spontaneous secretion of Na and Cl in IBSD. GCDC reduced the lumen to plasma fluxes of Na and Cl equally in both groups. The jejunal patterns were like the ileal. No changes in the transmural PD were demonstrated. The small intestinal epithelium in IBSD, besides being prestimulated by some at present unidentified agent (e.g., prostaglandins or gastrointestinal hormones), shows an increased sensitivity to the stimulus of GCDC, which may have therapeutic implications.