INTESTINAL FUNCTION FOLLOWING ALLOGENEIC SMALL INTESTINAL TRANSPLANTATION IN THE RAT

Abstract

This study tests the hypothesis that small bowel transplantation alters the function of the intestine. The function of the small intestine was investigated after syngeneic (BN----BN or Lew----Lew) and fully allogeneic (BN----Lew) orthotopic total small intestinal transplantation (SIT) using a two-stage model. All animals were treated with cyclosporine A throughout the 60-day study period. Syngeneic transplantation reduced weight gain in the (BN----BN) rats, but not in the (Lew----Lew) animals. Allogeneic transplantation caused a reduction in weight gain for the first 30 days posttransplantation, which may have been associated with graft-versus-host disease. Thereafter, the rate of growth of allogeneic SIT animals was normal. Dietary fat absorption was reduced in all groups of transplanted animals. Intestinal permeability to mannitol and polyethylene glycol 400 (PEG-400) was increased by syngeneic transplantation in all groups, with further permeability increases to mannitol, lactulose, PEG-400, and 51Cr-EDTA after allogeneic SIT. The glucose-stimulated intestinal short circuit current was reduced by both syngeneic and allogeneic SIT, but the maximal active transport rate for glucose uptake was increased, as was the passive uptake of fatty acids. These functional alterations were not associated with changes in intestinal morphology or evidence of rejection. These findings demonstrate that: (1) SIT results in significant changes in the transport characteristics of the bowel, but these have a minimal impact on the well-being of the animal overall; (2) SIT induces an increase in intestinal permeability to mannitol and PEG-400, with a further increase in permeability to all markers following allogeneic SIT; (3) following SIT, and the immune events associated with allogeneic SIT, significant adaptation of the transplanted intestine occurs. We suggest that denervation of the small intestine after SIT is the underlying cause of the changes observed.