Bradykinin stimulates t-PA release from intact vessels, but not from endothelial cells in culture. It has been proposed that the nerves of blood vessels are the source of bradykinin stimulated t-PA release. In order tho test this hypothesis, we intend to infuse bradykinin into the brachial (arm) artery and the coronary arteries of heart transplant recipients and control subjects. This is because heart transplant recipients do not have nerves to their coronary arteries.