Electron microscopic study on permeability of coronary artery wall of normotensive rabbits using horseradish peroxidase as a tracer

In order to study the pathways in the coronary artery vessel wall horseradish peroxidase (HRP) was used as a tracer. HRP was injected directly in the left ventricle of rabbit hearts. 30 seconds after intracardial injection of HRP in normotensive rabbits, peroxidase reaction products could be located in random areas of the coronary arterial system and could then be observed in all three layers of the coronary walls at these locations. HRP reaches the subendothelial space of the coronary arteries along two pathways: through intercellular junctions and by plasmalemmal vesicles. Through the fenestations of the internal elastic lamina HRP reaches the media and can be detected between the media smooth muscle cells. The influence of the methodology on the results is discussed.