ENTEROCYTE FUNCTIONAL ADAPTATION FOLLOWING INTESTINAL RESECTION

Following massive small bowel resection, the remaining intestine under goes compensatory adaptation to maintain absorptive capacity, The purp ose of this study was to determine the relative importance of mucosal hyperplasia and functional adaptation by individual enterocytes in thi s process. Distal ileum was harvested from rats 2 weeks following 70% small bowel resection or transection with reanastomosis. Transport par ameters were determined in Ussing chambers, Short-circuit current (I-s c) responses to additions of 3-O-methylglucose were measured to assess Na+/glucose cotransporter kinetics. Microvillus absorptive surface ar eas were calculated with computer-assisted morphometric modeling. Thes e surface area values were used to normalize transport parameters, Ile al absorptive surface area was 70% greater in resection tissues than i n transection tissues (P < 0.05). Na+ and Cl- fluxes were generally lo wer in the resection group. Na+/glucose cotransporter Delta I(sc)max ( an index of cotransporter quantity) for resection and transection tiss ues were 0.3 +/- 0.1 and 1.8 +/- 0.3, respectively (P < 0.05). K-m (an index of cotransporter affinity for substrate) did not differ signifi cantly. Following intestinal resection, ileal surface area increases; however, transport parameters, when normalized to absorptive surface a rea values, diminish. During early postresection adaptation, expansion of ileal absorptive surface area due to hyperplasia seems to play a g reater role than upregulation of enterocyte Na+, Cl-, and glucose abso rption. (C) 1996 Academic Press, Inc.