The effect of intestinal autotransplantation on serum diamine oxidase activity.

Circulating levels of diamine oxidase (DAO), a mucosal enzyme found primarily in the small intestine, have been shown to reflect intestinal mucosal damage in a variety of disease states. Our aim was to assess the usefulness of both basal and postheparin DAO activity as a marker of intestinal allograft rejection by studying the influence of the nonrejection effects of intestinal transplantation on these activities. This separation of the immunological from all other effects of transplantation was achieved by studying 11 dogs who had undergone autotransplantation of the small intestine and 11 unoperated controls. Basal serum DAO activity increased during the first 3 postoperative days following autotransplantation (20.5 +/- 0.7 units/ml on Day 3 versus 6.9 +/- 4.1 units/ml preoperatively, P less than 0.05) but thereafter returned to control levels at 1 month and remained so for more than 18 months. Postheparin DAO activity was similar in both groups with a maximum increase between 15 and 60 min following heparin administration. There was no correlation between maximal DAO activity and time since operation in the transplant group. Intestinal DAO activity was similar to unoperated animals 18 months after autotransplantation. These findings suggest that postheparin serum diamine oxidase activity is not influenced by autotransplantation and thus, is a potential marker of graft rejection following intestinal allotransplantation.