Energy metabolism during transplantation rejection

The effect of transplantation rejection on energy metabolism is unknown. In order to investigate energy expenditure changes in this setting, we used an eight-cage rat indirect calorimeter to measure resting energy expenditure (REE) in the well-defined model of rat cardiac transplantation. Preoperative baseline measurements of REE were performed on Lewis recipients of allogeneic (Wistar Furth) or syngeneic (Lewis) heterotopic abdominal cardiac grafts (80.3 +/- 3.3 kcal0.75/day). Postoperatively, REE was measured on days 1 through 10, 15, and 20. An abnormal REE was defined as a greater than 10% change from the preoperative value. All cardiac allografts were rejected on postoperative day 7, whereas syngeneic hearts contracted for more than 100 days. Both groups of animals had a hypermetabolic response to surgery on postoperative day 1 compared with preoperative values (93.0 +/- 7.6 kcal/kg0.75/day, p less than 0.01). On postoperative day 2, REE normalized to preoperative baseline values in the syngeneic group and remained unchanged for the duration of the study (80.4 +/- 1.0, p = 0.49). In the allogeneic group, on postoperative days 3 through 6 an abnormal REE was recorded in 22 of 28 measurements compared with only 3 of 16 in the syngeneic group (p less than 0.001). After transplant rejection, REE normalized to preoperative values in the allogeneic group. Characteristic changes in energy expenditure occur during transplantation rejection. These changes in REE preceded rejection in this animal model.