SYSTOLIC MECHANICAL PERFORMANCE OF HETEROTOPICALLY TRANSPLANTED HEARTS IN RATS TREATED WITH CYCLOSPORINE

Objectives: The aim was to compare left ventricular mechanical performance of the heterotopic cardiac transplant undergoing atrophy and the in situ recipient hearts of immunosuppressed rats. Methods: The hearts of outbred male Wistar rats were transplanted, with a part of the lungs, into the abdomen of recipients of the same strain by attaching the stump of the aorta end to side to the abdominal aorta of the recipient. The animals were treated with cyclosporin A at a daily dose of 15 mg.kg-1 for seven consecutive days after the operation. Ventricular function was assessed in the isolated perfused ''non-working'' heart under isovolumetric conditions. Results: Within three, 14, and 28 days after transplantation the mass of the left ventricle of the transplant decreased to 84, 54, and 43% compared with corresponding recipients. The developed pressure, maximum rate of pressure development, and the slope of the systolic stress-strain relation were unaffected in the atrophic ventricles of the transplants; the rate of relaxation, however, significantly decreased. Similar results were obtained with inbred Lewis rats receiving no immunosuppression. Conclusions: The data indicate that systolic mechanical performance of the heterotopically transplanted hearts was maintained during the development of atrophy; the cardiotoxic effect of cyclosporin did not manifest itself under these conditions.