Scanning electron microscope studies of rabbit aortic endothelium in areas of haemodynamic stress during induction of fatty streaks.

Young male rabbits were fed a diet containing 0.2% cholesterol for 4, 6, 12 and 20 weeks. At death the aortas of each animal were prepared for scanning electron microscopy (SEM) and the size of the atherosclerotic lesions surrounding the aortic ostia was measured by planimetry. Under SEM the early fatty lesions appeared as small discrete swelling of the endothelial cells. These cells were often larger than normal endothelial cells and their cell boundaries stained poorly with silver salts. Large confluent lesions were observed distal to the aortic ostia both 12 and 20 weeks after commencement of the diet but were still found to be endothelialized. No lesions however were observed immediately proximal to the entrance of an aortic branch. Haemodynamic forces, such as a high shear force, were presumably responsible for the localisation of these lesions.