Use of a Heterotopic Cardiac Isotransplant for Pharmacological and Toxicological Studies*

Abstract

The heterotopically transplanted rat heart provides a unique model for examination of the direct humoral effects on the myocardium since the transplanted heart is exposed to the same hormonal milieu as the in situ heart but does not support the hemodynamic load. In this model, the heart of an inbred rat is transplanted into the abdomen of a recipient of the same inbred strain by attaching the stumps of aorta and pulmonary artery end to side to the abdominal aorta and inferior vena cava of the recipient. The transplanted heart is perfused by the recipients' blood through the coronary vessels. It left ventricle beats mostly isovolumically and at a slower rate than the heart in situ. The transplant functions as a denervated "non working" Langendorf heart and does not appreciably contribute to the haemodynamics, while the recipient in situ heart supports the haemodynamics and serves as a control heart. The above model has been used to study the direct and indirect effects of thyroxine, catecholamines and of physical exercise on the cardiac mass and on its structure, function and chemical composition. It can also be used to study the acute and chronic effects of unloading and subsequent reloading. It can also shed some light upon the effect of denervation and potential reinnervation of the myocardium.