MOLECULAR ANALYSIS OF THE ADAPTIVE RESPONSE OF INTESTINAL BILE-ACID TRANSPORT AFTER ILEAL RESECTION IN THE RAT

Background & Aims: The apical sodium-dependent bile acid transporter i s critical for intestinal reclamation of bile salts, Its expression an d activity, along with the ileal lipid-binding protein, were studied b efore and after intestinal resection in the rat. Methods: The effects of surgical resection and bile acid feeding on the expression of ileal bile acid transport were assessed by a combination of functional (tau rocholate uptake into crude brush border membrane vesicles) and molecu lar assays (Northern and Western blotting), Results: Transport, apical sodium-dependent bile acid transporter and ileal lipid-binding protei n messenger RNA and protein expression were restricted to the distal 3 0 cm of ileum. After resection, transport and expression were limited to the remaining portions of this segment, Limited ileal resection inc reased protein mass and, therefore, transport in the terminal 5 cm of ileum without a specific increase in transporter gene expression, incr eased bile acid presentation to the terminal ileum did not induce ilea l hyperplasia. Eighty-five percent intestinal resection led to ileal h ypertrophy and a specific repression in bile acid transport activity. Conclusions: Native and compensatory bile acid transporter gene expres sion occur predominantly in the terminal 30 cm of ileum. The specific ileal responses to intestinal resection are dependent on the extent of resection.