RECEPTOR-SPECIFIC EFFECTS OF ACUTE REJECTION AFTER HEART-TRANSPLANTATION ON ENDOTHELIUM-DEPENDENT CORONARY RELAXATION IN DOGS

To establish the effects of acute rejection on coronary artery endothe lial reactivity in a canine model of heart transplantation, we submitt ed seven mongrel dogs to heterotopic heart transplantation without imm unosuppression for a period of 7 days. At harvesting, all transplanted hearts displayed a grade IV histologic rejection. Compared with nativ e heart, the endothelium-dependent relaxation of the coronary arteries from the graft displayed an increased sensitivity to serotonin, a dec reased sensitivity to thrombin, and no change in the response to acety lcholine and adenosine diphosphate; endothelium-independent relaxation to sodium nitroprusside was not affected. Therefore, in the canine he terotopic heart transplant model, acute rejection has no effect on end othelium-independent relaxation of coronary arteries but affects endot helium-dependent relaxation in a receptor-specific manner.