In vivo transmural potential difference: an early monitor of rejection in small bowel transplantation.

To determine if serial measurements of transmural potential difference (TMPD) can serve as an early monitor of rejection in small bowel transplantation, three groups of rats were studied. The groups are defined as follows: (1) group 1, isolated loop (N = 5): 20 cm of distal jejunum was defunctionalized (Thiry-Vella loop); (2) group 2, isotransplant (N = 5): 20 cm of distal jejunum was isotransplanted between inbred Lewis rats, as a Thiry-Vella loop; the native bowel remained in continuity; (3) group 3, allotransplant (N = 8): allotransplantation as in group 2 but between outbred Sprague-Dawley rats. Using luminal and peritoneal electrodes, TMPD was measured serially every third day. Biopsies of the stoma were taken on the same days for histologic examination of rejection. Group 1 animals (isolated loop) did not show a significant decrease in TMPD from day 1 to day 20. Group 2 (isotransplant animals) had a significant decrease in TMPD as compared with group 1 on day 5 (P less than .01), but by day 8, TMPD returned to baseline. Biopsies in groups 1 and 2 showed no signs of rejection. Group 3 (allotransplant animals) showed a significant decrease in TMPD as compared with group 1 on day 5 (P less than .01). The severity of the histologic signs of rejection parallelled the TMPD decrease throughout the remainder of the study. Monitoring TMPD is a sensitive method of detecting early rejection in small intestine transplantation.