Objective: To establish mouse-to-rat heart transplantation for the rejection of xenografts. Methods: NIH mice and Wistar rats were served as donors and recipients respectively. Heart from the donor was transplanted heterotopically into the recipient. The aorta of the donor heart was anastomosed end-to-end to the right common carotid artery of the recipient and the pulmonary artery was anastomosed end-to-end to the right external jugular vein using a microsurgery technique. Xenograft function was assessed by daily palpation

and the day of rejection was defined as the day when no pulsations could be detected in the transplanted heart. The rejected xenografts were analysed histologically. Results: 15 times of transplantation were done with the successful rate of 87%. The mean survival time of the xenografts was 2.15±0.90 days. The histology of the rejected xenografts showed widespread intravascular thrombosis

less hemorrhage associated with a large number of infiltrated inflammatory cells

focal ischemic infarcts and coagulative necrosis. Conclusion: These data suggest that mouse-to-rat heart transplantation with its simplicity

easiness and reliablity

is a good model in studying xenotransplantation.