Serotonin (5-HT): an enteroendocrine marker of rejection after small bowel allotransplantation in the pig.

The histopathologic findings of mucosal epithelial cell injury in acute and chronic rejection in small bowel transplantation are well known. Several studies have been done on the pig either as autotransplantation, allotrans-plantation, orthotopic, or enterotopic transplantation, with or without immunosuppression. Very few investigations on the enteroendocrine system have been done. In particular, none have been done on rejection in pigs after intestinal transplantation. On the other hand, changes in the enteroendocrine markers (somatostatin and chromogranin A) have been examined in detail after auxiliary small bowel transplantation in dogs without immunosuppression, showing no apparent changes on the 7th postoperative day, even if in a severe rejection status. Recent studies on rats have evaluated the presence of serotonin after small bowel allotransplantation with different times of preservation, and after reperfusion. The authors concluded that the number of serotonin-positive cells decreased with a preservation time of more than 1 hour in Ringer lactate at 4°C. We too have examined the modifications of argentaffin as well as serotonin-positive cells in the harvested small bowel of pigs perfused with Belzer solution (4°C) and preserved in Ringer lactate at 4°C, after preservation and reperfusion in the combined liver-small bowel allotransplantation. We noticed that the argentaffin and serotonin cells were preserved up to 20 hours and that after reperfusion the most important injury was due to the disappearance of these cells from the crypts. In this study, we studied the modifications of the intestinal enterochromaffin cells after combined liver-small bowel and small bowel alone allotransplantation in pigs, with the aim of evaluating a correlation with rejection.