BINDING OF [H-3] 5-HYDROXYTRYPTAMINE TO HUMAN CORONARY-ARTERY AND BYPASS GRAFT VESSELS

Objectives: 5-Hydroxytryptamine (5-HT) has a wide range of vascular ef fects mediated via specific receptors and it has been suggested to be a mediator in ischemic heart disease, The aim of the present study was to localise the 5-HT receptors within the vessel wall. Methods: Epica rdial coronary arteries obtained from patients undergoing cardiac tran splantation, internal mammary arteries from heart donors and saphenous veins from patients undergoing coronary bypass surgery, were sectione d and incubated with [H-3]-5-HT for in vitro receptor autoradiography. Results: Microscopic analysis of high resolution autoradiographic ima ges revealed a similar pattern of [H-3]-5 HT binding in epicardial cor onary and internal mammary artery, where it predominated in the lamina muscularis. In the saphenous vein, binding increased towards the adve ntitia which showed dense, displaceable binding to the vasa vasorum as well as to nerve-like structures, from which binding was only partial ly displaced. Computer-assisted densitometric analysis of low resoluti on autoradiographs revealed a high degree of specific binding to all v essels examined. Conclusions: The distribution of the [H-3]-5-HT bindi ng is different in the saphenous vein compared to epicardial coronary and internal mammary artery. The dense binding to vasa vasorum in the saphenous vein suggests a role for 5-HT in closure of these nutrient v essels, which could contribute to the formation of atherosclerotic cha nges in saphenous vein grafts.